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eSATA RAID boxes

Discussion in 'TiVo Series3 HDTV DVRs' started by Diacritical, Oct 10, 2006.

  1. Diacritical

    Diacritical Member

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    Jan 10, 2003
    Brooklyn...
    I am starting to put aside some duckets for an eRAID box for that great day when they allow expanded capacity (the S3 is full.. no room for suggestions).

    Does anyone have any sense whether RAID5 will work for this? We tend to avoid RAID5 in my business because of write bottlenecks and go with RAID1+0 -- but I don't want to waste that much capacity if I do not have to. I'm looking at a 2.5TB RAID5 array that might do the trick. if RAID5 is a problem with SATA drives, might I get past that by going to a SAS array with an eSATA connection? I don't want to spend more than $2-3k on this, but I will if it will make a difference. Noise is not a problem since it will go in an acoustical enclosure with it's own cooling unit, next to my home PC's SAS RAID arrays.
     
  2. NetJunkie

    NetJunkie New Member

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    Charlotte, NC
    RAID5 w/ SATA will be just fine. Remember, it's using a single SATA right now. Yes, you'll lose some write performance with RAID5 but with 3 drives you'll be fine with the increased spindles.
     
  3. rockhome

    rockhome New Member

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    Unless you are going to invest in some serious hardware, RAID 5 is all but useless. Typically, in large storage applications, the hardware is tailored with large, on disk caches and other tuning to make RAID 5 useful.

    If you are buying an off the shelf product from a consumer electronics store, I'd recommend RAID 0 at the most, that is really all you need. A lot of the decisions sort of depend on how the eSATA port on the S3 will be managed. RAID 5 is wholly unnecessary and could cause some problems if you lose a drive.
     
  4. jlib

    jlib Lean Forward

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    Nov 21, 2002
    Carmel...
    As opposed to losing a drive in a RAID 0 config? ;)

    I think the only reason to consider RAID 5 is to avoid problems with losing a drive. Someone considering a multi-Terabyte RAID is probably interested in not losing 6 months of saved movies and shows and all of their Season Passes. You are probably right about the performance limitations but Tivo is an unchallenging application and any write bottlnecks would not likely be approached even with two simultaneous write streams and one read.
     
  5. rodalpho

    rodalpho New Member

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    RAID5 is the way to go. Tivo doesn't need great write performance, and you can't beat the savings over RAID1 and 1+0.

    RAID0 is foolish.
     
  6. AbMagFab

    AbMagFab What happened, TiVo?

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    Feb 5, 2001
    My main server is a ~2TB RAID5 array in my PC with all SATA 3GB drives. Not eSATA, but per your original question, no issues with RAID5 and SATA.

    And you can use write-through or write-back, the latter for much improved write performance (at the expense of data loss if you're really unlucky with a hard outage at the wrong time).

    My only mistake was not using a large enough power supply. Seagate's have the best warrantee, but don't support staggered start up, so it's a big hit on power when they all spin up at the same time (for 8 x 320GB, it's about 270W of power on a full start). Just some advice from experience - get the biggest power supply you can get (I have a 650W in my PC that's has the RAID5 array in it).
     
  7. Diacritical

    Diacritical Member

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    Jan 10, 2003
    Brooklyn...
    Thanks, folks. I am willing to try a cheaper RAID5 solution first -- if it fails I can always use it somewhere else and replace it with a more robust RAID1+0 unit.

    RAID0 is not a serious option and RAID1 does not offer enough capacity to be worth the effort -- but RAID5 (very economical, fast reads, slow writes) may well work fine. When you consider the actual transfer rates (6MB/hour/stream???), all you should need is fast seek times for it to work well...

    Now for the interesting part -- getting eSATA enabled and figuring out just how large a volume the TiVo will support.
     
  8. Jazhuis

    Jazhuis New Member

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    Aug 30, 2006
    I do have one theoretical question; do any of the raid enclosures you're looking at do auto-repair and rebuild? While I'm sure there are some (for the $$$), I'm thinking that there certainly won't be any software interface through the S3 to initialize a drive replacement and subsequent rebuild.

    Edit: Yeah, while I can find drive arrays that have, for instance, an ethernet port for web-based configuration, I think most people will be far below the $10k rack-mount storage device range. Anyone have some sort of insight?
     
  9. JamieP

    JamieP Member

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    Aug 2, 2004
    Keep in mind that the MFS file system can't be larger than 2TiB (512 byte block size with 32 bit unsigned integers for block addresses = 2^41 = 2TiB).

    There are already some display problems when you go above 1TiB, presumably due to a few places in the code where signed integers are being used for size-in-blocks calculations. More details in this thread.
     
  10. rodalpho

    rodalpho New Member

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    Sep 12, 2006
    Yeah, all of the enclosures with hardware RAID will do that, configured via serial port or web browser. The cheaper ones actually have multiple sockets to connect to your computer for software RAID, they won't work with the Tivo. Or at least not in RAID. Hardware RAID eSATA enclosures aren't consumer-level items right now; they're only used in linear editing and such. Expect to pay over $800 for the enclosure alone.
     
  11. c3

    c3 TiVoholic

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    Silicon...
  12. rodalpho

    rodalpho New Member

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    Sep 12, 2006
    That's only two disks. RAID5 requires at least 3. It supports raid1 or raid0. Good for data protection, I guess, although you still have a non-mirrored disk inside the tivo.
     
  13. Diacritical

    Diacritical Member

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    Jan 10, 2003
    Brooklyn...
    I would only procure hardware RAID that does not require any support (aside from the eSATA interface) from the TiVo at all. All good hardware RAID enclosures will automatically rebuild (and I will have a hot-spare installed as well). In fact, connecting such a box is not impossible with TiVo as she is -- but I don't want to open the box and I'd much rather use the port once it is enabled.

    This is not cheap, but it is worth the effort.

    --
     
  14. jlib

    jlib Lean Forward

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    Carmel...
    JamieP, thanks so very much for that heads up. I too have been contemplating rigging up a hardware RAID (in my case in lieu of the the internal drive). That bit of information will keep me on track in not going so overboard on capacity that I cause other problems.

    Rodolpho, just in the last few months the market has been flooded with cheap Taiwanese hardware-based consumer RAID 5 enclosures (using single path SATA or eSATA host interfaces). There usually is little if any technical support for these products so buyer really needs to examine the website of the manufacturer to make sure they provide at least firmware updates (the chip is the thing with these units).

    Here is the thread that c3 mentioned. It got a bit off the original subject but is now about the whole RAID thing (substituting for the internal drive in particular). Interested readers may be able to cull some information out of it but this is a more appropriately named one.
     
  15. rodalpho

    rodalpho New Member

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    Sep 12, 2006
    Can you link to any? I'd love to setup an array with four cheap staples-special 250GB drives for the tivo.
     
  16. greg_burns

    greg_burns Now in HD

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    May 21, 2004
    Slower...
    http://www.cooldrives.com/sata-raid1.html

    Specifically...
    http://www.cooldrives.com/harasaiipomu.html

    Does this mean this wouldn't work with an S3? Does the S3's eSata port of have this circuitry? :confused:
     
  17. jlib

    jlib Lean Forward

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    Carmel...
    RAID 5; $290.05. This looks the same as the Accusys unit so they are probably the OEM. A user would want to go with an external power supply I think rather than tapping into the S3 power with 3 drives. For about $1K you have a fault-tolerant 1 TiB of storage (assuming 3 of the super quiet WD Caviar 500GB drives).
     
  18. c3

    c3 TiVoholic

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    RAID 0 and SPAN (concatenation) modes would work with TiVo, but you have to set up the box through a PC. It is very unlikely that TiVo's SATA hardware is port multiplier aware, but you do not need that functionality when the box is configured as a single virtual drive.
     
  19. jlib

    jlib Lean Forward

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    Nov 21, 2002
    Carmel...
    For our application the following terms in the description on a RAID enclosure equal incompatibility (i.e., they require controller cards or software drivers): Port Multiplier, Multilane, Infiniband and any with individual cables to the hard drives instead of one to the enclosure.
     
  20. c3

    c3 TiVoholic

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    Sep 8, 2000
    Silicon...
    Some boxes can provide more features with a port multiplier host and/or host software, but they can also be run standalone (compatible with TiVo) with less functionality.
     

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