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    Momentus XT Raid 0

    Discussion in 'Hardware Components and Aftermarket Upgrades' started by edd666999, Aug 30, 2011.

  1. edd666999

    edd666999 Notebook Guru

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    i know this is possible but what id like to see (if anyone has links please show me!) is the Momentus XT raid 0 benchmarked against 2 500gb 7200rpm drives in raid 0.

    i want to see this purely to see if the nand flash really is doing its job in raid.
     
    edd666999, Aug 30, 2011
    #1
  2. woofer00

    woofer00 Wanderer

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    woofer00, Aug 30, 2011
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  3. newsposter

    newsposter Notebook Virtuoso

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    early on in it's lifecycle, a lot of people tried to use the Momentus XT in raid groupings.

    Didn't work all that well, there was a lot of problems ranging from poor performance to data corruption.

    Seagate released a series of firmware updates that tried to 'fix' the cache coherency problems with the XT series in raid configs.

    Performance didn't improve all that much as compared to raid sets built with other disk drives. Benchmarks are spectacular, but real-world performance isn't all that special. Anyone who really needs high-performing disk arrays (not just fanbois bragging rights) buys SSDs and appropriate controllers anyway, not consumer-grade mechanical drives run by consumer-grade controllers.

    But the data corruption errors did in fact 'go away'. It's been speculated (but not proven) that Seagate had to tell the XT line to detect when they were in a raid set and if so, completely disable the flash memory cache.
     
    newsposter, Aug 30, 2011
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  4. chimpanzee

    chimpanzee Notebook Virtuoso

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    strange. A drive is a drive and if putting it into RAID can cause data corruption, something is very wrong, afterall it is accessed via LBA and nothing else.
     
    chimpanzee, Aug 30, 2011
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  5. newsposter

    newsposter Notebook Virtuoso

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    too many layers of cache that don't talk to each other. Or as the Brits say "too clever by half......."

    That was the problem with initial XT in raid configs. There is no way for the Momentus XT cache layers to coordinate with each other nor is there any way for the raid controllers/software to communicate with or control the XT flash cache.

    Works fine/spectacular as standalone drives though.
     
    newsposter, Aug 30, 2011
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  6. Pirx

    Pirx Notebook Virtuoso

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    I never had a problem with mine, of any kind.

    That is nonsense. My RAID array clearly shows the typical behavior of the XT cache with obtaining significant speed-ups in boot times after repeatedly rebooting, and loosing those speedups when forcing the drives to repeatedly read data that are unrelated to files that are read while booting. The XT cache is active in RAID as well.

    There is no reason why these caches would have to talk to each other. None at all.

    Again, there is no need to implement any such communication or control. All the XT does is remembering what blocks are accessed frequently, and caching those. This strategy is valid no matter how the disks are used, and in what kind of RAID they are.

    Works just as fine in RAID.

    Of course, not to be misunderstood, your comment about the limited performance gains of the kind of cheap RAID solutions (as in laptop chipsets) we are talking about here is entirely valid. People should not expect wonders from such configurations. On the other hand, they are solid performers, in my experience.
     
    Pirx, Aug 30, 2011
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  7. newsposter

    newsposter Notebook Virtuoso

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    anyway, there is a whole momentus XT thread already in place, the mods could probably merge this with that one........
     
    newsposter, Aug 30, 2011
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  8. chimpanzee

    chimpanzee Notebook Virtuoso

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    I am with Pirx on this one. The drive cannot know it is in RAID(and should not) so if there is any corruption, it is more likely to be at the RAID layer(probably bugs as XT may response too fast due to the cache) rather than the drive layer.
     
    chimpanzee, Aug 30, 2011
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  9. jclausius

    jclausius Notebook Virtuoso

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    It really depends on the RAID level. I've been running RAID-1 w/ out a problem since I installed the drives last November. I've seen some posts that RAID-0 will work and others where RAID-0 lost data integrity, and finally RAID-5 is a crap-shoot.

    In any case, Seagate does not support the Momentus XT in any RAID configuration, so you're a bit on your own here.

    For addt'l info, see:

    RAID - Seagate Community Forums

    Any problems Momentus XT in a RAID 5 using Intel I... - Seagate Community Forums

    http://forum.notebookreview.com/sag...ger-np7280-owners-lounge-485.html#post7607300
     
    jclausius, Aug 31, 2011
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  10. sgogeta4

    sgogeta4 Notebook Nobel Laureate

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    IMO, for most consumers and especially on notebooks (Intel software), RAID0 is not worth it. For a two drive configuration, you're almost always better off with a small SSD (64GB is plenty for most users for OS and programs) and a HDD (say 1TB).
     
    sgogeta4, Aug 31, 2011
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  11. edd666999

    edd666999 Notebook Guru

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    Thanks for the replys guys, i have seen many people run it successfully. How ever I didn't know Samsung and WD both now make 1tb laptop drives that fit, so im going 64gb ssd and one of those.
     
    edd666999, Aug 31, 2011
    #11