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save hd movies to blu ray or series of hard drives?

Discussion in 'TiVo Home Media Features & TiVoToGo' started by markmarz, May 25, 2012.

  1. lrhorer

    lrhorer Active Member

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    Aug 31, 2003
    San...
    No it wouldn't. A RAID5 array with 4 spindles should be faster than a RAID1 + 0 array with 4 spindles. Essentially, with the RAID1 + 0 array, data would be reading or writing to two drives simultaneously, while the RAID5 array will be reading or writing the same amount of data to 3 drives, with a corresponding increase in speed of nearly 50%, all else being equal.

    My 8 spindle RAID6 array can read and write data in excess of 450 MB/sec, which is far, far faster than any of the individual drives can be read or written.

    See my response above. Implementing a regular data sync, rather than mirroring represents a better example of not putting all the eggs in one basket.

    I have never been able to discern any loss in PQ using the default options in VRD. I've looked quite closely.

    Not just then. It's up to four times faster transferring to a THD and 3 times faster transferring to an S3. The space savings is also significant from a cost savings, both in terms of the investment in drives and the reduced power costs. Twenty drives use considerably less power than 30.

    Of course I was especially glad of the decreased storage size when the flooding in Thailand caused the prices of hard drives to skyrocket. Recoding to h.264 prevented me from having to buy new drives when 3T spindles were over $350 a pop.
     
  2. markmarz

    markmarz Member

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    Feb 3, 2002
    Chicago, IL
    Wow! What a thorough & well ordered reply! Thanks!

    It's a lot for me to digest .. the only thing I'm not convinced of is your statement that the BR discs will almost certainly have to be replaced in 10 years, and so on.

    How do you figure? I haven't had to replace a single dvd-r as yet, and some of them are over 10 years. Of course I haven't checked every single one of them, just a random sample driven by what I want to watch. But aren't blu rays less likely to fail than dvd-r? I'm not saying they won't fail (for anyone who wants to put words in my mouth); I'm trying to weigh the likelihood vs the cost of hard drives.
     
  3. lrhorer

    lrhorer Active Member

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    Aug 31, 2003
    San...
    You're welcome.

    The Library of Congress has run extensive durability tests on digital storage media. They very widely not only from manufacturer to manufacturer but even between batches from a single manufacturer. Some DVDs faded to complete unusability in under 3 years. Others have held up well for over 10 years in the same environment. The thing is, there is no way for a consumer to tell whether the media he is using at the moment will wear well or poorly. Ten years is a very good number to reach without any data loss. Of course, the environmental conditions make a huge difference. If kept in ideally low temperatures at ideal humidity in complete darkness in an antiseptic environment, recordable media can last much, much longer than media subjected to excessively high or low humidity, high temperatures, and onslaught by mold and fungus. My brother, for example, turns off his air conditioner completely when he is away from the house, and the daily temperature regularly soars to 40C or above. My house, however, has temperature controlled rooms where the temperature never exceeds 25C. Most, but by no means all, of my digital recording media, and all of my commercially recorded discs are still intact AFAIK. None of my brother's media more than 10 years old is.

    I don't know for a fact, but I doubt it. Of course, as I mentioned, DVD-R media varies a great deal in its longevity.

    I'm just not sure it's a terribly meaningful comparison.

    Note one thing, BTW. You had mentioned the cost of power keeping drives spinning. It is a significant cost, to be sure. One can, however, do some things to mitigate those costs. One is to shut down the array when not in use. The drives can then be allowed to spin down. Bringing the array back up only takes a few seconds. This can be especially practical for the backup. One can have the array automatically dismounted and disassembled after the daily rsync, and then fired up every day before the rsync. (Yet another advantage of not employing mirroring.)

    The last time I checked, mdadm did not support the automatic spin-down of RAID members, but that was several months ago, and it may now be supported. Of course, purchasing green drives and slower drives at the outset will also help. For most residential users, the loss in performance is more than offset by the increase in performance engendered by employing an array, assuming it is an issue in the first place.
     
  4. pmiranda

    pmiranda New Member

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    Feb 12, 2003
    Austin, TX
    A couple last notes on my comments...
    My RAID5 is dog slow since it's basically running in software. If you have a hardware controller it should indeed be faster than a single drive.
    I use GoodSync to "mirror" between computers, with it setup to automatically add files in one direction and only at chosen intervals, but it won't delete anything without user intervention and it won't do the sync if more than X% of the fileset changes. If you inadvertently modify a file this won't help, but for this stuff that would almost never happen anyway. I'm sure you can get the same effect with other, free, software as well.
     
  5. lrhorer

    lrhorer Active Member

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    Aug 31, 2003
    San...
    Untrue. In years past, hardware RAID was faster than software RAID, but it has not been true now for well over half a decade. With today's multi-GHz 64 bit processors, software RAID is almost always faster than hardware RAID. What's more, true hardware RAID is pretty rare, only found in very high dollar RAID controllers. Most so-called RAID controllers and RAID motherboards run what is known as "fake RAID", which is actually software RAID embedded on the controller and implemented through the BIOS.

    If you are having problems with speed, unless you are running an ancient 386 or something, it isn't due to the slowness of software RAID. I am running md RAID under Debian "Squeeze" Linux on two fairly old AMD Athlon 64 x 2 processors, each with a little $45 four port HBA, and as I mentioned, the systems are easily capable of reading and writing in excess of 450 MBps.

    What is true is the RAID implementation is limited by the speed of the expansion interface. If your drive controller is a simple PCI card, it will be limited by the 133 MBps bandwidth of the PCI bus. PCI-x or better yet PCI-E adapters are preferred, since both are much faster. PCI-E interfaces can support up to 8GBps in both directions. Of course older drives with slower interfaces, slower spin rates, and smaller caches will also perform more poorly than more modern, higher speed drives.

    Multi-lane RAID implementations are also much faster than Port Multiplier implementations, but also much more costly, and usually not able to support as many spindles overall. PM implementations are more than sufficient for most home users, though. I did run a multi-lane system for a while, but currently I am using Port Multipliers.

    Yeah, Linux. Free OS, free RAID software (mdadm), free sync software (rsync), free scheduling software (cron). 'Fast, easily configurable, and stable as granite. 'Downloadable anywhere. 'Available for just about every platform imaginable.
     
  6. markmarz

    markmarz Member

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    Feb 3, 2002
    Chicago, IL
    This has been a great discussion, I appreciate everyone's input immensely!

    I'm now leaning more towards the hard drive array solution, provided I can find a green solution and keep the initial investment low. I like the idea of having the drives spin down etc; in fact I see no need to keep the system up at all (especially backup) until needed. I'm not even sure I need to run raid .. but all this is better handled in another thread. There's probably lots already on the subject so I'll browse around and if I have something not handled in an existing thread, I'll open a new one.

    Going to keep a particular lookout for lrhorer's contributions.

    Thanks!
     
  7. jcthorne

    jcthorne Active Member

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    Jan 28, 2002
    Houston

    Yes, good idea. He has been instrumental in my NAS media server setup. Lots of good information there. Spend some time reading his old posts as much of this subject has been already covered.
     
  8. fyodor

    fyodor Member

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    Sep 19, 2006
    Some of this has to come down to your preferred viewing experience too.

    I think that for many people here a viewing experience in which you have to first decide what you want to watch, run upstairs, find the disc, and play it from a single location, is extremely nonoptimal.

    People like to be able to have all of their movies remotely browsable and watchable, which you can't do with 2700 blu-ray discs.
     
  9. fyodor

    fyodor Member

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    Sep 19, 2006
    AVSforum used to have a sticky in its HTPC subforums for media servers. That might be a good place to look.

     
  10. FeliciaCorrine

    FeliciaCorrine New Member

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    Apr 18, 2012
    I prefer the external Hard Disk Drives over blue ray's.......because they are rewritable.
     

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