Newbie iso Help Choosing/Understanding NAS to store 6-9TB digital media forTivo Acces

Discussion in 'TiVo Home Media Features & TiVoToGo' started by lynnalexandra, Dec 18, 2011.

  1. lynnalexandra

    lynnalexandra Member

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    I'm ready to think about getting an NAS. I have just about filled up about 5TB with Tivo'd video (one full expanded Tivo HD 2TB, one upgraded 2TB Premier and a 2TB external hard drive connected to my PC). Between all my videos - and well over 1TB of music (lossless format), I clearly need a better way to store it than multiple external hard drives. So I've looked over the other threads and I think what I need is a NAS storage device. I'd like it to hold our evergrowing amount of video, music, pictures and documents. I'd like to be able to stream the video and music (through the Tivos) and the music through the Tivo and into a home audio-video receiver.

    I have set up the Tivo to publish the folders of video and music that are stored on my external hard drives. I have my living room Tivo outputing audio to the home a/v receiver. Right now the connection is with a Tivo Wireless N adapter, but I"m planning to run a cat6 cable so that the Tivo is directly wired to the router.

    Now I think I need an NAS that can house 4-5 drives. A few people have recommended the synology NAS and I think this is the way to go, but I could use some guidance.

    I am a newbie at this. I believe I need an NAS to be DNLA compatible (but I could not really tell you what that means beyond more digital formats can be accessed more easily- I may be confusing this with a need for a home media server to be DNLA compatible. Is the Tivo DNLA compliant? Is that sufficient? Should my a/v receiver be DNLA compliant too?).

    Anyway, I want at least 4 bays - and the option to expand would be useful. I've seen folks here rave about this synology DS1511 scalable NAS:

    http://www.amazon.com/Synology-Disk...?s=electronics&ie=UTF8&qid=1323232357&sr=1-13

    A less expensive model is the Synology DS411J:

    http://www.amazon.com/Synology-Disk...?s=electronics&ie=UTF8&qid=1323232357&sr=1-24

    From what I can understand, the 1511 is a higher level model for two reasons. A fifth bay - and it can be expanded on by simply buying and connecting this expansion unit:
    http://www.amazon.com/Synology-Plug-n-Use-Expansion-Attached-DX510/dp/B003DTLXKG/ref=pd_sim_e_2


    No need to set up another NAS - just add this onto it.
    -------------------------------------------------
    .
    Are there other features to this DS1511 5-bay system that makes it better than the 411? Is it pricier because it has features that are way beyond what I need? I think I saw mention of monitoring from cameras - and remote access - features that I don't think I need. I just want to store my digital media, a few other documents - have back-ups - and be able to access this information from any home-networked device (or maybe that would be handy - but not necessary).

    Some features I would like:
    1)reasonably easy user interface

    2) being able to have any home-networked device access the files stored on the NAS
    3) be able to use different sized drives. So I can use the 2TB drives I already have (one filled with Tivo video and the other new and blank so far). And then potentially add some 3TB drives. Can NAS's hold differently sized drives? Can I add them on as I go or do I have to set them all up at once?
    4) if I start with 2TB drives - and in the future 3-4TB drives become reliable, inexpensive and available, can I swap drives and replace the 2TB drives with larger drives

    No doubt there is software and other considerations that go into choosing a suitable NAS. Is there anything else I should consider? Or is it so complicated that it's better to just tell me to just take your word for it?

    And then there's the question of what is RAID? what would I want? Raid0,1,5, unraid. I don't know anything about what these mean and I see here that people have set up their devices differently.

    Thanks for any help. I'm sorry this isn't very coherent. I'm sure I'll learn as I go and be able to fine-tune my questions more.

    Thanks.
    Lynn.

    PS - if it matters, I currently have a dell inspiron 530 with Windows XP. In the next year or so I'll probably get a new desktop with Windows 7. Does the operating system of my pc matter in terms of setting up the NAS? Any problems with switching the desktop operating system in a year or so?
     
  2. xekester

    xekester New Member

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    If you are interested in exploring using a NAS, check out http://www.smallnetbuilder.com/
    If you are considering a Synology unit try http://forum.synology.com

    I just recently got the 411J, but I am too much of a NAS newbie to be much if any help to try and directly answer your question. So take your time with your research; there are many different NAS vendors out there, and a lot of resources for DIY builders as well.

    Xekester
     
  3. jcthorne

    jcthorne Well-Known Member

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    I have the Synology 1511 and could not be more pleased with it. My reasons for choosing it over the 411J were:

    Future expandability and glad I did, I would have outgrown the 411J in less than a year. I now have the 1511 and one 510 expansion with one drive in it (6 drives) in a Synology Hybrid RAID format.

    Larger memory and faster processor in the 1511 means file server and media serving run ON the NAS. Pytivo, squeezebox and vidmgr. DLNA and Squeezebox are Synology supported apps. Pytivo is supported by its developers.

    Online drive replacements and upgrades. Don't underestimate this. Even for home use. Add a 3TB drive to an existing array can take several days to complete. The 1511 allows insertion of the new drive and will add to the existing array while in use.

    RAID in general gives you some redundancy in the event of a drive failure. Its not the same as a backup. I run a Synology Hybrid RAID format with single drive redundancy. This means if any one drive in the array fails, the NAS promts me to replace the failed drive and then rebuilds the arrray without loss of data. The hybrid raid is very similar to standard RAID 5 except that it handles varyious drive sizes and online updates of the array.

    To your specific question, yes you could use several 2TB drives you currently have and add 3TB drives in the future to add space to the same array.
     
  4. Phantom Gremlin

    Phantom Gremlin Active Member

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    I have no personal experience with the Synology products but have been keeping my eye on them.

    I'll throw out a slightly lower priced product that may not be expandable enough for the thread starter, but may be useful to others reading this:

    Synology sells the DS712+ which starts out with 2 disks and allows use of the same 5-disk DX510 expansion that the DS1511+ supports. This combination may be of some interest to people who want to save some money and don't think they will need more than 7 drives total.
     
  5. wmcbrine

    wmcbrine Well-Known Mumbler

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    The TiVo does not speak DLNA, only its own protocols. If the NAS doesn't explicitly list TiVo support as a feature, you may be able to add third-party software to it, like pyTivo, to handle that.

    The OS of your PC should be irrelevant. The NAS has its own OS. It's possible the makers of the NAS will distribute some junkware with it, but it should have a web interface, telnet daemon, etc.
     
  6. lrhorer

    lrhorer Active Member

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    There is a law of nature - hereafter known as lrhorer's law, which states that no RAID array is ever large enough for more than a short period of time.

    Now, I'm not going to stand here and say a NAS is a bad idea. For some people and some applications they are fine. There is also a place for hardware RAID and even fakeRAID systems. The proper place for them, however, is a low end system that does not need to be expanded or upgraded beyond a certain point. For anything larger than 5 drives, I definitely recommend a Linux based server, not a canned NAS. I also recommend at a minimum RAID6, and a good, solid backup solution. I would also stay as far away from non-standard schemes that allow things like asymmetrical arrays. No matter what the type of array, stick with one drive size, or at least one member size, for the array.

    Yes, these restrictions do imply spending more on the array, at least in the short run, but they will prevent a great many headaches over time, and may even wind up costing less in the long run.

    The great thing about a Linux RAID array is it is based upon a massively supported set of tools, allows for maximum flexibility, and is easy to maintain and upgrade. If one runs into a problem, the mailing lists can usually come up with an answer in a matter of hours, and most of the lists are monitored by at least one of the principle developers of the application. Most Linux distros can be installed free of cost and take only about 45 minutes to set up. My preferred distro is Debian. Debian is as rock solid as it comes, and when setting up a server, rock solid is a very important thing. Both of the RAID servers in my house have been up nearly seven months, and the only reason both were shut down then was there was a prolonged power outage at my house which exhausted both UPS units. The last time I performed any maintenance on either array was last year when I replaced all the 1T drives on the primary array with 3T drives, dropping from 15 drives to 8.

    I am not saying anyone else must follow my example, but I do suggest you think carefully before deploying something in great measure different. Ultimately, going a different direction may not be a poor decision, depending upon one's needs, but it should be a carefully considered one.

    My two RAID servers consist of a pair of Antec 4RU rackmount enclosures to house the CPUs and the boot drives, and not much else. (I got them cheap - I would not spend a lot of money on the CPU housing.) The motherboards and CPUs are fairly modest AMD Athlon 64 x 2 systems on decent Asus motherboards. The HBAs are also nothing special - just a pair of $25 Port Multiplier compatible PCIe x4 cards. I am a big fan of keeping the boot drive system separate from the data system. In this case, I just took four old 500G drives (which are way, way overkill: 80G is more than plenty) I had lying around and partitioned them into 3 partitions each. Each has a tiny /boot partition of 50M, a very large swap partition of 20G, and the rest partitioned as the root. Each system has 2 of the boot drives installed with each partition paired with its twin in a RAID1 array.

    I then bought first a 12 drive Port Multiplier RAID chassis and then later a 20 drive Port Multiplier RAID chassis from PC Pitstop as the systems grew. The main array consists of eight unpartitioned 3T drives combined into a RAID6 array. The backup server hosts twelve unpartitioned 1.5T drives also combined into a RAID6 array. Both arrays are formatted as XFS.

    The primary server is running pyTivo, kmttg, SAMBA (and SWAT), HME for Python, vidmgr, Galleon, openvpn server, DHCP, Apache2 web server, SSMTP, and NCID, plus it acts as a backup controller for the system which controls my HVAC system. The backup server is running an rsync job that backs up the primary server every morning at 04:00, plus it is also the primary controller for my HVAC system. It also runs DDNS, Apache2, and SAMBA.
     
  7. lrhorer

    lrhorer Active Member

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    It is worth noting many people have done that very thing.
     
  8. unitron

    unitron Well-Known Member

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    And unitron's ammendment/corollary to that is that nothing used for file storage is ever large enough for more than a short period of time.:D

    (not even if it's only paper files in a cabinet)

    As to the OP's original question/dilemma...

    If possible, you might want to stall the decision, while continuing research, to see if drive prices come back down any next spring when makers are supposed to be recovered from the Thailand flood damage that choked off the supply chain and ran prices up so dramatically recently.
     
  9. jrtroo

    jrtroo Chill- its just TV

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    Personally, I use a homebuilt version of the first WHS. It meets all of your feature requirements, can be done with last generation hardware, and could be a cheap solution that backs up everything in the entire house. It is easy to expand capacity, add/subtract discs, supports pytivo, TTG, ect.
     
  10. Soapm

    Soapm Active Member

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  11. lynnalexandra

    lynnalexandra Member

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    Wow. It's hard to know where to start. First - thank you to everyone for your generousity in responding to my query. Unfortunately, most of these posts are way beyond my level of comprehension.

    JCThorne - your response was encouraging. If an NAS is what I need, it makes sense to get one with a faster processor, and expandability. Glad to hear you like your 1511. Also glad to hear I can mix drive sizes (although it sounds like lrhorer does not necessarily agree with that - but I don't understand the potential complications). Also good to know that the system stays up and running if a drive needs to be added/replaced. That's a consideration I hadn't considered - thank you.

    Lrhorer - my grasp of what you're saying is so limited, I am not sure I should take more of your time asking for clarification. But if you are inclined, there are so many questions. I think for starters that I may not understand what system you are propposing - and how that is different than an NAS. I don't really know what an NAS is. I thought it was just something that housed multiple drives so that they could all be accessed on the network (I did know it had some type of software and processor). Beyond that, I don't know what I"m looking for - except large capacity, reliability and being able to stream video over the home network (for the most part that's in the living room and wired).

    I love the law of nature and corollary - that no storage is enough for long. I remember first upgrading my Tivo back here June 2009 - and being wondering how I could possibly need more than 2TB of storage. Of course, now I'm way over that.

    I don't know what linux is (although I have a vague sense that it's an operating system of sorts - and open sourced).

    I don't really know what RAID is (I know what it stands for - just not what it is). I certainly don't know what a hardware RAID and even fakeRAID is. Don't know what Raid 0, 1, 5 or hybrid means - so I have no idea what guides that choice. I do think your solution is going to remain well beyond my capability - but I think you're got a lot of wisdom - some of which I may be able to grasp.

    On another note, I first considered this NAS before the Thai floods and increase in drive prices. I'm not in a rush to buy the drives if what I have is sufficient - the 2TB drive nearly full, a new 2TB drive and a new 1.5TB drive. So if it's okay to mix sizes, will that be enough to start? Does the choice of Raid eliminate a lot of space. I have a vague notion that the drives make copies of themselves - so depending on the type of Raid, only a certain portion is available for new files. Is that much right?

    Any guidance on type of RAID - or where to go for a quick RAID, NAS for dummies (not a whole book, please - but happy to get more educated by being pointed somehwere.

    Thanks everyone.
    Lynn
     
  12. Soapm

    Soapm Active Member

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    While someone is answering lynnalexandra question can you also riddle me this...

    Lets say I have 4 2TB drives in a RAID 6. How much data can I store? 2TB... 4TB... 8TB...
    Why would I need a backup solution if the failure of one drive means I can simply insert a new drive into the array and it will heal itself?

    I'm just wondering if it's worth the cost for movies that will eventually come on again or DVD's where you still have the original in mint condition???
     
  13. lrhorer

    lrhorer Active Member

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    Not so much a faster processor. A NAS doesn't do much in the way of number crunching. The exception might be if you intend to use the NAS' processor to do a lot of full video recoding of HD material. In that case I recommend at least 6 of the fastest cores you can find. Expandability is a must in my opinion.

    It certainly can be done, but it is not supported in any of the standard RAID implementations, to my knowledge, and for good reason. LVM supports it, but performance will almost surely suffer, and redundancy is certain to be problematical. Of course there is nothing wrong, if you happen to get a good deal on a 3T drive or two, installing them in an array with 2T spindles and only using 2T for the time being.

    Don't count on that working very well if the drive sizes are all different. It also depends on the implementation. LVM doesn't directly support redundancy. RAID, OTOH supports various levels and types of redundancy.

    RAID0 employs no redundancy, but only stitches together a number of devices to make one large volume. Performance increases are huge, however. The loss of a single device may take down the array and lose a large amount of data, possibly all of it.

    RAID1 employs simple mirroring. A RAID1 array is composed of two or more essentially identical devices. All but one of these devices can fail without taking the array offline.

    RAID5 offers the ability to set up an array of N + 1 devices, where any single device can fail without taking down the array, and the size of the array is equal to N * C, where C is the capacity of each device. Performance increases are also usually very large, but not as large as a RAID0 array.

    RAID6 is similar to RAID5, except any two devices can be lost without taking the array offline. If the total number of devices is N + 2, the array capacity is N * C. I recommend RAID6 any time the number of data elements exceeds 6 (6 data elements + 2 parity ).

    RAID levels can be combined. For example, RAID 1 + 0 can take a number of RAID1 arrays and stitch them into a single large array. Each RAID1 element can lose all but one of its members.

    There are lots more options, including RAID10, RAID50, RAID60, etc., but they are generally beyond what the home user would ordinarily consider.

    Properly speaking, a NAS is an embedded device dedicated to the purpose of sharing files over a network. Most are based on some flavor of Linux, but like the TiVo, most have a very limited, canned UI - usually web based. Some utilize proprietary protocols and require specialized drivers for access. I would avoid these. Most NAS systems have their OS in a flash system, or possibly even in ROM. In general, to run more applications than those with which the NAS is packaged will require hacking the NAS. Some are easier to hack than others. Most NAS systems do not even have the ability to attach a keyboard, mouse, and monitor. There are exceptions.

    By comparison, a Linux system is just that: a more or less ordinary PC running Linux. The only thing particularly specialized about it is the attachment of a RAID chassis, if needed. There are plenty of tower cases that can house 8 or 10 drives, but beyond that, one probably needs an external drive enclosure capable of holding many drives. There is nothing wrong, however, with starting simply with a small tower capable of holding 5 or 6 drives and upgrading later. The beauty of a Linux system is there is no hacking involved. One simply loads whatever software one wishes. That, and of course the software is all available free of charge. For a starter system, you can probably pick up a used tower for under $200 and add a handful of medium-large drives. For a better fit, get a nice multi-bay tower from Newegg or Tiger Direct (or whatever) and pick up a decent, middle of the road motherboard and CPU along with enough SATA ports to handle the number of drives you intend to put in the system. Again, for robustness, ease of management, ease of configuration, and ease of installation, I recommend getting a small, inexpensive hard drive for booting, and leave the big boys exclusively for data. An 80G drive is more than plenty. 40G is fine. 10G is a bit small, especially if you want a desktop GUI.

    That's a very broad brush. You need to focus your intent a bit more. First of all, what is your budget? What is the most you intend to spend up-front?

    Secondly, you need to think about just what reliability means to you. RAID systems are fault tolerant, but they do not provide a replacement for a backup strategy. If you do not have a good backup strategy in place, then eventually you WILL lose data - maybe all of it. How much do you want to spend on your backup solution, and how comprehensive does it need to be? For example, are you willing to differentiate between videos you cannot abide losing versus some which won't give you great heartache to lose? If so, you can afford to limit the scope of the backup system and save some time and money. If not, then the backup solution is going to have to be able to store at least a bit more data than the primary solution. Beyond that, just how reliable does the system need to be? Is it of extreme importance the system never be down under any circumstances? In that case, a high availability dual chassis system employing mirrored networks and drives with extensive UPS units is required. With Linux, this is easy, but expensive. If you just want to be able to get the system online quickly and easily when it does go down, then a single online system fills the bill quite well. If you want a system that almost never goes down in the first place, but is not guaranteed never to go down, then a simple Linux server is your best bet. Depending on exactly what you need, the system can range from a couple of hundred dollars (plus the cost of the data drives) to many thousands of dollars.

    Exactly. My best advice is to not lock yourself into a system that can only be expanded a limited amount.

    Not "of sorts". It is an operating system. A real one. Most Linux applications are open source. Some are not. There are quite a few different distributions - most of them available free of charge. Typical Linux distros include 20,000+ applications. You probably won't need all of them. :)

    The one I prefer for most deployments is called Debian. It is available at www.debian.org. The latest stable version is called "Squeeze", and includes some 29,000 software packages. There are also a lot of Debian derivative distros. The most popular is probably Ubuntu. Ubuntu is aimed more at the user who wants to have all the latest bells and whistles. Consequently, it is not as stable as Debian, but it has all the latest features. The other main set of distributions are derivatives of Red Hat Linux. Red Hat and Debian developed two different methods of packaging their software elements, as well as two different ways of managing the software on the live system. I prefer Debian's approach, although both have their strong points.

    Hardware RAID implements the RAID functions in hardware. Hardware RAID used to be faster than software RAID, but no longer since CPUs have gotten so blazingly fast. Software RAID also used to eat up a lot of CPU resources, but once again, now that CPUs are so fast, the overhead from RAID is insignificant. Hardware RAID cannot be upgraded except by replacing the RAID controller entirely. (The exception being the UI, which may reside in flash.) FakeRAID implements software RAID directly on a controller card. It tends to enjoy the worst of both worlds. Some controllers claim to be hardware RAID, when they are really fakeRAID. I recommend software RAID. It eliminates interoperability issues with the OS, and may be more stable. It is readily upgraded. These days it is faster than hardware RAID. Non-RAID controllers and fakeRAID controllers with their RAID software disabled are cheaper than hardware RAID.

    I suggest you read up on RAID and also on Logical Volume Management. In the mean time, I posted a short comparison above.

    Not really. Once you have decided on a system to implement (don't worry too much if it's wrong at the outset - fixing it is not too difficult if you proceed with a small amount of caution and ask before you leap), it's not that difficult. If you have a decent broadband connection, downloading one of the Debian netinst .iso files and burning it to CD-ROM only takes a few minutes. After that, installing a basic Debian system is quite easy, and only takes about 45 minutes. Once the OS is up and running, if you choose a Desktop (GUI) environment, there is a fairly decent drive manager automatically provided that does a pretty good job of creating and managing a RAID array. Barring that, mdadm is easy to use, and as I mentioned, has tons of support via the mailing list. The principle developer, Neil Brown in Australia, is very active on the list, as are a few dozen other very experienced people.

    I hear you. I am thrilled I upgraded my arrays a few months ago with enough space to last more than a year and a half.

    LVM allows one to mix sizes, but it takes a severe performance penalty to do so. Standard RAID implementations do not allow mixing device sizes, but one needn't use a whole drive as the device. On could, for example, partition the 1.5T drive into three partitions and the 2T drives into four partitions, and use the 500G partitions as array elements. One can take the elements and piece them together in such a was that no single drive failure will take down the array. Off the top of my head, however, I can't think of an arrangement that won't eave at least one 500G element unused, but still can survive the loss of any of the drives intact. What's more, a RAID5 implementation will take one unit over and above the total number of data elements as a parity element. In the simplest implementation, this means one drive. If you split up the drives into 500G partitions, this means at least 2T, unless you wish to take a chance on one of the 2T drives failing. It's your data, but I certainly don't recommend it. At the very least, I would look for another 2T drive on sale, or better yet two. What you could do, if you feel like gambling a little, is get a single 2T drive, and then create a RAID5 array with a missing drive. This will allow you to create a 6T unprotected array. As soon as you come across a bargain on another 2T drive, get it and add it to the array, healing it. From that point on, any single drive can fail without taking the array down.

    Files of any sort (new or old), yes. RAID1 employs mirroring. It can be a two, three, four, or more way mirror, but all of the data of the array is held in toto on every element of the array. Thus, a RAID1 array made of four 1T drives can only hold 1T of data, but any three of the four drives can fail completely and simultaneously without taking down the array. By comparison, a RAID5 array made of six whole 1T drives can store 5T of data, and any one drive can fail without taking the array down. A RAID6 array made of six whole 1T drives can lose any two drives without failing, but only holds 4T of data.

    One more thing: although booting from a RAID5 or RAID6 array is possible, I don't recommend you try. At most I recommend RAID1 on the boot devices. You can create small boot partitions on the larger hard drives for booting, but it is so much easier and less troublesome to simply use a small drive or two exclusively for booting.
     
  14. lrhorer

    lrhorer Active Member

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    4T, assuming the array is not degraded. RAID6 is probably not the best choice for a 4 element array, although there can be valid reasons to choose RAID6 for a 4 element array.

    What happens when that one drive catched fire, and destroys two other drives? I have had 4 drives fail simultaneously. Last year I had four Seagate Barracuda drives in a single array bite the dust together. I also had a power outage right in the middle of expanding an array from ten drives to twelve. The array was taken offline, but I was able to start a recovery of the upgrade, when the power failed again. All of the data structures more than 16K in size were massively corrupted. A few hundred text files survived, but the video files all looked horrible, with tons of pixellation. Without a backup I would have been in deep pookey. As it was, it took two weeks to recover all the data and another two weeks to verify it all.

    The odds of losing two drives in a matter of an hour is not very high, but it can take several days for the data to be rebuilt. What happens if another drive fails, and then another?

    Finally, while drive failures certainly occur, the most common cause of lost data is operator error. One of my favorite movies is the original Superman, with Christopher Reeve, Margot Kidder, and Gene Hackman. I was doing some work on the metadata file when I accidentally overwrote the video file with the metadata file. The video was unrecoverable. I did not have a backup of it. I kicked myself weekly for over three years until it aired again.

    Do yourself a huge favor. If any data is even slightly important to you, back it up.

    That's a judgement call, and entirely yours. If you wish to arrange the movies by importance and only back up the ones you really, really don't want to lose, you can save yourself some money. If you decide no movie is so important that you would be bothered to lose it, then you can save yourself a ton of money. Just don't be bothered when all the movies go POOF!!.
     
  15. Soapm

    Soapm Active Member

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    I really don't get it. Six 1Tb drives will get you 4TB. Four 2TB drives will get you 4TB.

    I try and try to understand RAID but I guess I'm limited to 2TB drive = 2TB. Want more space get another drive. Pray you don't have a drive failure and burn any movie you must keep to a disc...
     
  16. lrhorer

    lrhorer Active Member

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    Sometimes a picture is worth 1000 words. Here is a screen-shot of a remote session on my video server (running Linux). I elected to run a desktop (not usually the best practice for a server) because there are several GUI based applications I want to run on that server, including kmttg. Notice it in the background. The foreground should also be familiar. In the upper right corner you can see I have 17T total storage from /dev/md0 mounted on /RAID, which is the local data array, and 14T total storage on the array mounted on /Backup, which is local to the other server. You might also take note of the storage from /dev/md2, mounted on /. That is the operating system. It is using 13G out of 302G total. I could very easily have used a 20G or 40G drive, but I had the old 500G drives laying around, unused. Also note the up time in the lower right corner: 4774 hours ( 199 days, or 6.5 months ).

    [​IMG]
     
  17. Soapm

    Soapm Active Member

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    Wow, 12T worth of data??? Is it possible to watch that many shows???

    I see how much space you have and obviously there are no 17'T drives that I know of but how many individual drives do you have making up the 17T and the 14T?
     
  18. lrhorer

    lrhorer Active Member

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    San...
    Again, if N is the number of devices (not necessarily drives, it can be partitions, files, whatever), then N - 2 devices carry the data, and 2 devices carry parity. The data can be re-constructed from any N devices, whether those devices carry the actual data or the parity informaton. Eight 1T drives in a RAID6 array hold 6T of data. Twelve 1T drives hold 10T of data. (Actually, the architecture of RAID6 allows for more than 2 parity drives. I believe the code allowing for 3 or more parity drives in Linux is under development right now. For more than 12 data drives, 2 parity drives is a little thin.)

    I don't know what you mean, here. Any data that is important needs to be backed up. For the best security, the backup should be housed somewhere else, preferably at least 30 miles away. A fire can take out an entire house. A gas explosion can take out a whole city bock. An Earthquake can take out buildings across a whole sector of a city. Two or three drive failures can take out a RAID5 or RAID6 array. Its a great deal less likely than taking out a RAID0 array, though, which only requires a single drive failure. The odds of a single drive failing in the span of a year is pretty low, but certainly not zero. The odds of any one of ten drives in a 10T RAID0 array failing in a single year is pretty high.
     
  19. lrhorer

    lrhorer Active Member

    6,933
    10
    Aug 31, 2003
    San...
    In what time frame? I have seen all but a few of the shows on the array. A bit over 2000, mostly movies: http://fletchergeek.homelinux.net:8080

    That doesn't include the DVDs.

    Code:
    RAID-Server:/RAID/Server-Main/Movies# mdadm -D /dev/md0
    /dev/md0:
            Version : 1.2
      Creation Time : Fri May 20 03:41:03 2011
         Raid Level : raid6
         Array Size : 17581590528 (16767.11 GiB 18003.55 GB)
      Used Dev Size : 2930265088 (2794.52 GiB 3000.59 GB)
       Raid Devices : 8
      Total Devices : 8
        Persistence : Superblock is persistent
    
      Intent Bitmap : Internal
    
        Update Time : Wed Dec 21 01:36:09 2011
              State : active
     Active Devices : 8
    Working Devices : 8
     Failed Devices : 0
      Spare Devices : 0
    
             Layout : left-symmetric
         Chunk Size : 1024K
    
               Name : RAID-Server:0  (local to host RAID-Server)
               UUID : 73143f23:62cff764:b4a47b8f:4dbf4316
             Events : 494630
    
        Number   Major   Minor   RaidDevice State
           0       8        0        0      active sync   /dev/sda
           1       8       16        1      active sync   /dev/sdb
           2       8       32        2      active sync   /dev/sdc
           3       8       48        3      active sync   /dev/sdd                                                                                                                                                
           4       8       64        4      active sync   /dev/sde                                                                                                                                                
           5       8       80        5      active sync   /dev/sdf                                                                                                                                                
           6       8       96        6      active sync   /dev/sdg                                                                                                                                                
           7       8      112        7      active sync   /dev/sdh 
    
    Backup:/usr/share/thermostat# mdadm -D /dev/md0
    /dev/md0:
            Version : 1.2
      Creation Time : Mon May 31 16:23:10 2010
         Raid Level : raid6
         Array Size : 14651371520 (13972.64 GiB 15003.00 GB)
      Used Dev Size : 1465137152 (1397.26 GiB 1500.30 GB)
       Raid Devices : 12
      Total Devices : 12
        Persistence : Superblock is persistent
    
        Update Time : Wed Dec 21 01:24:06 2011
              State : clean
     Active Devices : 12
    Working Devices : 12
     Failed Devices : 0
      Spare Devices : 0
    
             Layout : left-symmetric
         Chunk Size : 1024K
    
               Name : Backup:0  (local to host Backup)
               UUID : 431244d6:45d9635a:e88b3de5:92f30255
             Events : 436732
    
        Number   Major   Minor   RaidDevice State
           0       8        0        0      active sync   /dev/sda
           1       8       16        1      active sync   /dev/sdb
           2       8       32        2      active sync   /dev/sdc
           3       8       48        3      active sync   /dev/sdd
           4       8       64        4      active sync   /dev/sde
           5       8       80        5      active sync   /dev/sdf
           6       8       96        6      active sync   /dev/sdg
           7       8      112        7      active sync   /dev/sdh
           8       8      128        8      active sync   /dev/sdi
          10       8      144        9      active sync   /dev/sdj
          12      65        0       10      active sync   /dev/sdq
          11       9       10       11      active sync   /dev/md10
    
     
  20. jcthorne

    jcthorne Well-Known Member

    3,116
    196
    Jan 28, 2002
    Houston
    Just a quick note on the hybrid RAID arrangement used by Synology. For single redundancy in a mixed size arrray, the RAID volume = the total of all drives in the array less the largest drive. For double redundancy, its the same less the two largest drives.

    Any one drive fails, replace with a drive same size or larger and the array is restored.

    All hybrid RAID schemes are propritary and panented so are not in the public domain as are standard RAID arrangements. This limits the systems that can mix drive sizes to those that own the tech. Synology is one of those.

    For the same reasons I do not run a HTPC, the NAS made more sense for me than a DIY system. Its also very power efficient.
     

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