From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Brown Subject: Re: make filesystem failed while the capacity of raid5 is big than 16TB Date: Thu, 13 Sep 2012 09:13:11 +0200 Message-ID: <50518787.4010501@hesbynett.no> References: <505033fe.8aec440a.5d52.ffffe37b@mx.google.com> <50504094.2040302@hesbynett.no> <505059DD.8000108@hesbynett.no> <5051542A.4090901@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5051542A.4090901@gmail.com> Sender: linux-raid-owner@vger.kernel.org To: Mathias Buren Cc: GuoZhong Han , stan@hardwarefreak.com, linux-raid@vger.kernel.org List-Id: linux-raid.ids On 13/09/2012 05:34, Mathias Buren wrote: > On 13/09/12 11:21, GuoZhong Han wrote: >> Hi David: >> >> I am sorry for last mail that I had not described the >> requirements of the system very clear. >> >> I will detail for you to describe the requirements of the >> system. >> > > (snip) > >> >> As you said, the performance for write of 16*2T raid5 will be >> terrible, so what do you think that how many disks to be build to a >> raid5 will be more appropriate? > > Personally I wouldn't use more than 5 drives in a RAID5 with drives > larger than 1TB, the failure risk is too high. With 16x 2TB drives, how > about two RAID6 arrays of 8 drives each, then RAID0 them? (RAID60) > > Or, two RAID6 arrays with 7 drives each, 2 hotspares, and RAID0 on top. > (RAID10 + 2 HSP) > I wouldn't bother with hotspares with RAID6 unless service and replacement of a dead disk is going to take a long time - you already have double redundancy with the raid6. Raid6 on 8 disks is already orders of magnitude safer than raid5 with 16 disks - once you have a higher risk of the power supply taking fire and burning /all/ your disks, you don't benefit from even greater redundancy! > You mention 36 cores. Perhaps you should try the very latest mdadm > versions and Linux kernels (perhaps from the MD Linux git tree), and > enable the multicore option. > If that is possible for the OP, then that is definitely worth trying. It is this kind of setup that will benefit most from the newer multithreading support.