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Raid 10 with 2 NCQ drives a 2 non ncq drives

Posted on 2006-11-20
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I have a dell 9200 (ich8r) that supports 6 sata/esata drives.  The 2 internal drives are SATA 3.0Gbps (samsung SP2504C) drives.   I have a 3rd drive, a WD2500JS.
The 2 onboards have NCQ but the 3rd one doesn't.  I was planning on getting another WD2500JS to get a matched set, running them on/over eSATA and create a RAID 10.

So here's the problem/question.  Since I have 2 that support ncq and 2 that don't.  Is there a way to optmimize them drive arrangement to make use of NCQ?
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Question by:medic459
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by:btassure
ID: 17986581
Put one of each type of drive into the raid so that you have

SP2504C            \                        SP2504C
striped                |---> mirroring  
WD2500JS          /                        WD2500JS

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by:medic459
ID: 17989274
Why is that any more optimal than having both NCQ drives together?
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btassure earned 200 total points
ID: 17991350
It will keep the mirror balanced. As each block is written to either drive in the initial stripe it will be replicated to the same place on the other side of the mirror so there will be no lag. If the NCQ drives formed the first half of the mirror there will be a short delay for it to write to the other side of the mirror.
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by:Duncan Meyers
Duncan Meyers earned 800 total points
ID: 17991367
I doubt that its going to make a blind bit of difference to be honest. NCQ ( http://en.wikipedia.org/wiki/Native_command_queueing) will improve performance on the drives that support it (providing your controller supports SATAII). In a RAID 1/0 set, I'd suspect that you may see a minor read performance improvement (the more sophisticated RAID controllers can serve a read from either stripe set) if the two NCQ drives form one stripe set (then mirrored to the non-NCQ drives):

SP2504C            \                      WD2500JS
striped                |---> mirroring  striped
SP2504C            /                       WD2500JS


Its highly unlikely that you'd see any difference to write performance (write performance will be limited by the lowest performance drives) - but that largely depends on the RAID controller.

The best thing to do is try each configuration and run performance tests - just beware of the on-disc cache skewing results.

To take full advantage of NCQ you'll need aqll NCQ drives.
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by:btassure
ID: 17991384
I doubt it would make much of a difference either but I wanted the points :oP

It is also possible that the NCQ drives (being a tad more advanced) may have a faster spindle speed but I haven't looked up the disk specs. Either way I figure spreading the NCQ around would balance out the mirror.
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