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Re: Sata speed difference on G-RAIDS?

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Steve Modica
Re: Sata speed difference on G-RAIDS?
on Oct 27, 2012 at 5:20:28 pm

[Thomas Morter-Laing] "10024 501 1998 W 318081566 1048576 DiskSpeedTest ??/G-RAID 001/DiskSpeedTestTemp
and
10155 501 1998 R 317863890 286720 DiskSpeedTest ??/G-RAID 001/DiskSpeedTestTemp"


This says that it takes about 10msec for an IO. These IOs are roughly 1MB and 256K. 10msec for 1MB isn't fast enough for uncompressed stuff, but it's OK for Pro Res. If all the IOs are 1MB, that's not usually very efficient (although it depends on your raids stripe size). We aim for 4MB.

Obviously one or two IOs isn't going to break a stream (the app reads ahead), but if you see a lot of smaller IOs that take 10msec, that's not a good thing. As you might imagine, doing a 4MB IO isn't going to take 40msec. It might finish in 16msec. That would mean roughly 4msec per MB instead of 10msec.

Steve

Steve Modica
CTO, Small Tree Communications


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