From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Robinson Subject: Re: high throughput storage server? Date: Wed, 23 Feb 2011 14:25:49 +0000 Message-ID: <4D6518ED.1080908@anonymous.org.uk> References: <4D5EFDD6.1020504@hardwarefreak.com> <4D62DE55.8040705@hardwarefreak.com> <4D63BC6D.8010209@hardwarefreak.com> <4D64A082.9000601@hardwarefreak.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: David Brown Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 23/02/2011 13:56, David Brown wrote: [...] > Incidentally, what's your opinion on a RAID1+5 or RAID1+6 setup, where > you have a RAID5 or RAID6 build from RAID1 pairs? You get all the > rebuild benefits of RAID1 or RAID10, such as simple and fast direct > copies for rebuilds, and little performance degradation. But you also > get multiple failure redundancy from the RAID5 or RAID6. It could be > that it is excessive - that the extra redundancy is not worth the > performance cost (you still have poor small write performance). I'd also be interested to hear what Stan and other experienced large-array people think of RAID60. For example, elsewhere in this thread Stan suggested using a 40-drive RAID-10 (i.e. a 20-way RAID-0 stripe over RAID-1 pairs), and I wondered how a 40-drive RAID-60 (i.e. a 10-way RAID-0 stripe over 4-way RAID-6 arrays) would perform, both in normal and degraded situations, and whether it might be preferable since it would avoid the single-disk-failure issue that the RAID-1 mirrors potentially expose. My guess is that it ought to have similar random read performance and about half the random write performance, which might be a trade-off worth making. Cheers, John.