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OT: slow RAID speeds
I just installed 4 Western Digital WD2500KS SATA 2 drives in my Mac Pro dual 2.66ghz and RAID’d them using disk utility. Problem is I do not think I am getting the speed that these drives should be putting out.
Using Blackmagic Disk Speed Test, testing one single WD2500KS drive I get
a Read rate of 40.5 MB/s and a write of 50.2 MB/sI then RAID 4 of the same drives and test with same utility and get
a Read rate of 116.0 MB/s and a write of 179.6 MB/sI used Apple Disk Utility to RAID the drives and selected striped option and
Mac OS Extended (not journaled)any idea what this read rate is so slow? should it not be roughly 4 times the single drive rate, somewhere around 160 MB/s?
btw the drives did not come with jumpers and I did not use any, just put them in. I have the boot drive connected to the extra SATA2 port on the motherboard, the 4 drives are in the 4 Mac Pro drive sleds.
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4 Replies
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try this – (and you will think that I am nuts) –
try a RAID 0 with Apple Disk Utility of only THREE drives (not 4) – I bet your speeds increase. I saw a similar observation on http://www.barefeats.comBob Zelin
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I did try that, it did not help.
Striping drives 1,2,3 gave me 96 MB/s
then Striping drives 2,3, 4 gave me 98 MB/sI really have no idea why this is not working, puzzling.
Each individual drive gives me in the mid 40 MB/s no problem, together, I do not get the approx 200 MB/s I should.
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I can tell you that you should be able to get about 68mb/sec on a single SATA, and about 128mb/sec with only 2 SATA drives stripped RAID 0. The Hitachi and Seagate drives perform like this. It’s easy for me to say “try a different brand of drive”, but that costs money to do.
Bob Zelin
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Not sure what’s going on with your configuration. I have 3 Maxtor Maxlines in my Mac Pro 2.66 – Apple RAID 0 – read 192 / write 190 – 840 GB storage. I did set the RAID for 256K block size. There must be something with the WD’s. Can you exchange or return them?
Dan Sparks
Tricom Video
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