Re: RAID5
From: Nuno Souto <dbvision_at_iinet.net.au>
Date: Wed, 16 Nov 2011 20:55:48 +1100
Message-ID: <4EC388A4.9010605_at_iinet.net.au>
That's also what I've seen. I'd add that for sequential scans - FTS and other similar ops - there is not much difference in read speed between RAID5 and RAID10, assuming a stripe across a reasonable number of disks. I did notice in extreme multi-thread load situations that random reads are marginally faster in RAID10.
Writes however are a completely different proposition. RAID5 seems to be slower there across the board, compared to RAID10. Not sure if that's because the parity generation algorithms are notoriously slow, or some other reason. But it's a fact I've been able to confirm in various setups, from native attached disks to large SAN hardware.
Too early to say anything about our new Symmetrix.
Date: Wed, 16 Nov 2011 20:55:48 +1100
Message-ID: <4EC388A4.9010605_at_iinet.net.au>
That's also what I've seen. I'd add that for sequential scans - FTS and other similar ops - there is not much difference in read speed between RAID5 and RAID10, assuming a stripe across a reasonable number of disks. I did notice in extreme multi-thread load situations that random reads are marginally faster in RAID10.
Writes however are a completely different proposition. RAID5 seems to be slower there across the board, compared to RAID10. Not sure if that's because the parity generation algorithms are notoriously slow, or some other reason. But it's a fact I've been able to confirm in various setups, from native attached disks to large SAN hardware.
Too early to say anything about our new Symmetrix.
-- Cheers Nuno Souto in sunny Sydney, Australia dbvision_at_iinet.net.au Allen, Brandon wrote,on my timestamp of 16/11/2011 9:51 AM: > I'm curious why your reads were so much faster on the RAID10.Received on Wed Nov 16 2011 - 03:55:48 CST
> All else being equal, I'd expect to see the writes faster on RAID10
> vs. RAID5 (once your cache is exceeded), but not the reads.
> I suspect there was something else affecting the numbers other
> than just the RAID level. As with pretty much everything else,
> the correct answer on the RAID5 vs. RAID10 question is - it depends.
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