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RAID 0 - Real-world peformance on the home desktop?

Discussion in 'Storage Drives' started by Jimbo Mahoney, 19 Jan 2006.

  1. Jimbo Mahoney

    Soldato

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    Location: Belfast

    I'm always seeing people wanting RAID 0 arrays, even though they are using a fairly typical home setup of Windows + Games + MP3s.

    My personal opinion is that RAID 0 offers little, if any, performance improvement on the typical home desktop system, BUT, I would like to investigate this as fully as possible, partly because I too, ironically, am tempted with the RAID 0 bandwagon...

    My own belief, based on my understanding of a RAID 0 setup, is that there comes a point where the latencies of the discs are the limiting factor, something RAID 0 cannot address and in fact, may increase.

    So,

    Small files = latency is limiting factor

    Large, contiguous, files = transfer rate is limiting

    My question is, where is the turning point? Is it 500kB, or 1MB, or 100MB?

    So far, I've only managed to dig up a paper from 1996:

    http://archive.nlm.nih.gov/pubs/bangbuck/bangbuck.php

    From this, the fastest performing system (3 disk RAID 0+1) is only 9% faster than 6 simple volumes. Most of their files are <100kB.

    Does anyone have any idea as to the file size which means RAID 0 would be faster?

    Are there other factors to consider? (Apart from reliability, I'm only interested in this from a performance POV. Everyone should realise the increased risk in having data striped across multiple drives...)
     
    Last edited: 19 Jan 2006
  2. Jimbo Mahoney

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    Interestingly, I hadn't realised this before, but any files smaller than your chosen stripe size will only be written to one disk, eliminating ANY performance gain from RAID 0.

    Also, a little formula I found:

    Optimal Strip size = Average File Size / 2n

    where n is the number of drives the RAID controller 'sees'. For RAID 0 = all drives, for RAID 5 = all drives, for RAID 10 = 50% of drives. Always round the final figure down to the nearest stripe size permissible.

    EDIT - surely (Average File Size / n) makes more sense?

    also

    Optimal Cluster Size = Stripe/2


    Let me know if these hold water.
     
    Last edited: 19 Jan 2006
  3. Jimbo Mahoney

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    /watches tumble weeds roll by....

    :D

    I see noone makes an informed decision when buying RAID 0 setups then?

    /dons flame suit

    Or, I'm asking dumb questions...
     
  4. noxidjkram@hotm

    Wise Guy

    Joined: 29 Oct 2005

    Posts: 2,447

    Location: Newcastle upon Toon


    Interesting opinion.

    For 'normal' usage you are correct.

    For those of us who like Superfast Windows load (ooh i've saved 5 seconds - what will i do with it?), or those of us who need the game level to load quicker so we can get killing faster than anyone else, it has a use.

    There are also those of us who must just have the fastest and the best!

    Perhaps also there is some use for video-editing where large files are moved around...

    Otherwise, there's me. I have come to realise (after 2 years of RAID0 Raptoring) that those extra seconds do not matter to me for my usage, and that i prefer silence.

    [EDIT] RAID0 with the right drives definitely offers a huge performance boost in a specific area - disk access - but if you don't need it, its no use. [/EDIT]

    Hence the 'rig in the sig'.

    M
     
    Last edited: 20 Jan 2006
  5. semi-pro waster

    Man of Honour

    Joined: 27 Sep 2004

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    If the argument is they are unnecessary for an average home user then yes I'd say you are correct however if like I did you simply want to experiment then there is no harm in using Raid0 arrays providing you either have back-ups or don't store critical data on them.

    A Raid0 array does have its place but most people will not really see a major benefit, I have used Raid0 drives for about 3 years both as my primary boot drive and also as a single large storage drive and I can honestly say that the speed difference was negligible to me when I reverted back to single drives.
     
  6. noxidjkram@hotm

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    Well thats the argument base so far, but an expansion wouldn't hurt either (i.e. look at it from other users points of view) - might give some more perspective to it?

    M
     
  7. Jimbo Mahoney

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    I just wonder if there's been any benchmarks anywhere which relate to real-world usage with different file sizes, rather than just people flinging HDTach burst speeds around ;)

    Of course, having never used RAID 0 myself, I am also open to having my opinion changed.

    It is true that with smaller files, you are access speed-limited though, right? Or, does 0% fragmentation mean that they are effectively contiguous and the higher throughput of RAID 0 would help?
     
  8. noxidjkram@hotm

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    With any size file you will have the addition of the access speed.

    It will just be a smaller percentage of the total time on larger file accesses.

    0% fragmentation would mean the files were contiguous *if* the files you were getting were related in a way that the defragmentation process had accounted for, nothing else.

    The higher throughput of RAID0 should help on any size, it will just be more noticable on the larger files due to the percentage of total time reason mentioned above.

    M
     
  9. Jimbo Mahoney

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    Of course! (to both points).

    Ta.

    Does anyone know of a program which pulls up statistics of file sizes on a drive?

    Obviously, average is easy to do, but can be heavily biased. I found one piece of software which sounded promising, Simpl-File Statistics, but again, it only gives average, min and max and crashed when I gave it a drive to analyse because of the System Volume Information directory. Other statistics would no doubt be useful in helping determine stripe size or whether RAID would be beneficial or not.

    Thanks for the input so far. (all)
     
  10. Jimbo Mahoney

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    I also mean most of us here on OcUK without an OBVIOUS benefit, like video editing. Gamers / overclockers / average home users, but not people who edit 100's of MBs of video, as that is almost a case-closed scenario.

    I agree, but I'm questioning whether, in many cases, RAID 0 is any faster, except in HDTach. I guess there's the placebo factor to take into account, or the fact it makes you happier to know you have RAID 0 Raptors even though they don't really benefit you in the real world, which is fair enough.

    You want to get yourself some SilentStar WC enclosures! I have my two drives (one's a raptor) inside a Dual Silentstar and they are great! I used to use SilentDrives (and still do in another rig), but was worried about the Raptor inside one of them with little airflow (I'm WCing the whole rig and there aren't very many fans around).

    ROFL :D - When you buy the 74GB Raptor RAID bundle, you save 1p :D

    http://www.overclockers.co.uk/acatalog/westerndigital_sata.html
     
    Last edited: 20 Jan 2006
  11. noxidjkram@hotm

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    See 'rig in sig'.

    I have the SilentMaxx with one of the quiestest 250Gb HDDs there is.

    My whole system is fanless, and the only mechanical part is the HDD, (DVD and floppy are rarely used).

    It is (and i kid you not) effectively completely silent.

    I sleep in the same room, and cannot hear it even when defragging (as windows sometines does by itself) or downloading...

    M
     
  12. marc2003

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  13. joeyjojo

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    Nice find marc2003! Great piece of software
     
  14. G00SE

    Gangster

    Joined: 24 Feb 2003

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    this thread is most interesting.

    i have just gone from raid 0 ide to a single raptor (36gb) and the difference in tangable performance is not noticble!

    However, i thought this was due to exceptional performance from the raptor and i'm on the verge of getting another raptor for raid 0, hoping for a substantial increase in performance!

    HDtach showed my ide raid0 as being faster than the raptor, but like i said, actual noticable performance difference was, well..... not noticeable!!

    so maybe i should i save my hard earned!!
     
  15. noxidjkram@hotm

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    RAID0 raptors ARE fairly awesome though...

    Particularly the larger size drives!

    An ordinary drive (7200rpm) RAID0 is a tad better than a single drives... Raptors are special when in RAID0 (for some reason)... Or maybe its just me...

    M
     
  16. G00SE

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    you just auctioned 2 36gb's ;) i know cos i was gonna bid on one! :p

    you upgraded to 74's or 150's?
     
  17. Jimbo Mahoney

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    What was your stripe size and cluster size?


    Good work fella!
     
  18. Jimbo Mahoney

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    Any further input on the Optimal Strip Size being:

    Average File Size / 2n

    where n = number of drives over which striping will occur? (e.g. RAID 0 with two drives, n = 2, RAID 0+1 or 1+0 with 4 drives, n = 2).

    I'm sure

    Average File Size / n

    makes more sense?

    Anyway, on my work laptop, the entire HDD is one partition, and it breaks down like this (thanks Marc2003!!!):

    Distribution of sizes in C:\

    Size Interval % of Files

    Over 1 GB .......0.0%
    256 MB - 1 GB .....0.0%
    64 MB - 256 MB ....0.1%
    16 MB - 64 MB .....0.3%
    4 MB - 16 MB ......0.7%
    1 MB - 4 MB .......2.3%
    256 KB - 1 MB ......6.7%
    64 KB - 256 KB .....13.3%
    16 KB - 64 KB ......21.2%
    4 KB - 16 KB .......20.5%
    1 KB - 4 KB .......17.1%
    0 KB - 1 KB .......17.8%

    (no doubt the forums will mess up the table format)

    You can see that ~ 75% of my files are smaller than 64kB and ~90% are smaller than 256kB.

    I'd be inclined to go with a stripe size of 32kB for this system, or even 8kB since some 55% of my files are smaller than 16kB!

    Maybe most people are making their stripe size too large when RAID 0'ing at home?
     
  19. ByteJuggler

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    Surely we should be talking *median* filesize, as opposed to *average* filesize... that's what the size interval tables effectively give you... :confused:
     
  20. Jimbo Mahoney

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    Yeh, sorry, that's what I mean. You're right - average is silly.