Slooooow Raid performance...

Discussion in 'MacBook Pro' started by appleguru1, Oct 11, 2007.

  1. appleguru1 macrumors 6502

    Joined:
    Mar 13, 2003
    #1
    So, I've been running a 600GB raid0 array for a while now... 2x 320GB Seagate SATAII drives, connected to my C2D 2.33GHz MBP via an Expresscard SATA controller (Sil 3132).

    That setup gave me very good performance; consistently above 140MB/s read and write.

    Today I got in a 5 bay port multiplying SATA case, along with 4 new seagate 320GB drives... so now I have 6 drives total.

    Doing a raid0 stripe across all 6 drives gives me around 112MB/s, though sometimes even slower... Adding drives to a Raid0 should speed it up, not slow it down!

    A raid 10 (stripe and mirror, 3 drives in each striped set mirrored), gave a dismal ~55MB/s.

    ...Single bare drive performance is just over 79MB/s read and write.

    I'm in the process of building a raid 5 (using Silicon Image's SATA RAID 5 Manager) to test its performance, but I'm not too hopeful...

    The theoretical maximum for this setup is ~320MB/s, which I really shouldn't have any trouble hitting with 6 drives raid0'd. (This is the 2.5Gb/s limit of the express card slot... the SATA II limit for all hardware involved is 3Gb/s).... Even if for some strange reason the setup was defaulting to SATAI (and it shouldn't be... all hardware is SATAII compliant and all drives are jumpered to SATAII), I still should be getting 1.5Gb/s, or ~192MB/s.

    Any ideas as to why I'm getting such crappy performance?
     
  2. deadpixels macrumors 6502a

    deadpixels

    Joined:
    Oct 30, 2006
    #2
  3. appleguru1 thread starter macrumors 6502

    Joined:
    Mar 13, 2003
    #3
    I have a feeling I'm bumping into the (arbitrary?) 125MB/channel limit that appears to be on the card I'm using. Not sure where that's coming from, as SATAII is supposed to be 3Gb/s, but still:

    http://www.sonnettech.com/product/tempo_sata_express34.html

    (Different manufacturer.. same card: says there under tech specs, Data Transfer Rate: Up to 125 MB per second per port).

    So, given this information, theoretically I should have 2 drives per SATA port to maximize performance (A setup like that should give me ~240MB/s).. Unfortunately I only have one port multiplying case, so one channel can only have one drive.

    So, since the performance per channel is limited to 125MB/s, adding more than 2 drives to a channel wouldn't net me a performance gain (and may actually give me a hit), so... what I'll try next is a raid0 with 2 drives in the case on one channel, one drive on the other channel and a FW800 drive (It's a PATA drive, seems to max out at ~37MB/s by it self)... That 4 drive raid should, at least based on my calculations and real world testing, get me ~240MB/s, though I'm expecting more like 150MB/s... which would not be much better than my 2 drive SATA raid0 got me :/

    I'm expecting this lower value b/c when I had a 6 drive raid it spanned both channels.. and still only got me ~120MB/s...)

    We'll see soon though!
     
  4. appleguru1 thread starter macrumors 6502

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    Mar 13, 2003
    #4
    Alright, so that 4 drive setup gets me just under 150MB/s (149.7MB/s Write, 144.7MB/s read)... Hrm...

    Seems like my best bet for performance is to run a single drive per channel on SATA coupled with a FW drive (or two), striped.. should get me ~170MB/s... Let me try pulling one of the drives and connecting it via USB2.... 8)
     
  5. appleguru1 thread starter macrumors 6502

    Joined:
    Mar 13, 2003
    #5
    Throwing USB 2 in the mix doesn't help... speeds drop to 61.1MB/s Write, 71.0MB/s read (This is with one SATA drive on each SATA channel, one drive on FW800 and one drive on USB2).

    Lets try a 3 drive setup now, which based on my data should give me the best performance I'm going to get with what I have available... 1 SATA drive direct connect per channel (nix the multiplier), and 1 FW800 drive... 3 drive raid0.

    I'm predicting ~170MB/s.
     
  6. appleguru1 thread starter macrumors 6502

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    Mar 13, 2003
    #6
    3 drive raid0, 2x320GB SATA via independent channels and 1x 400GB PATA via FW800 gave me 117.5MB/s Write, 180.5MB/s read (Peak read during 1GB ram to disk write ~205MB/s... Peak Write ~129MB/s)

    ...Single drive in port multiplying case but otherwise same setup gave ~117.3MB/s Write, ~179.4MB/s Read)

    Other drives in case, mounted (in case... 2 in raid 10, 1 as bare drive, 1 as part of raid0.. 1 unused) gives roughly the same speeds.
     
  7. appleguru1 thread starter macrumors 6502

    Joined:
    Mar 13, 2003
    #7
    Sorry for spewing the boards with benchmarks... just want this to be somewhere on the net in case someone is looking for similar data :p

    4 drive raid0, 2 SATA on one channel, 1 SATA on the other channel, and one via FW800 gives write performance of ~150MB/s (Burst to ~174MB/s) and read performance of ~145MB/s (Burst to ~178MB/s)
     
  8. jamerson9 macrumors newbie

    Joined:
    Feb 11, 2007
    #8
    Thanks for the tests. The results seems to reinforces other peoples benchmarks with 3 drive raid 0. This is the first result I've seen with 4 drives. Doesn't seem to be worth going for more than a 2 drive raid 0, given the trade off between the improvement in performance and increased risk of drive failure.


     

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