From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tomasz Chmielewski Subject: RAID-10 and 4 HDDs - how many HDDs can break without loosing data? Date: Thu, 10 Aug 2006 10:49:37 +0200 Message-ID: <44DAF321.7090204@wpkg.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-2; format=flowed Content-Transfer-Encoding: 7bit Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids I want to set up RAID-10 on 4 400 GB drives, on a not-so powerful machine (600 MHz ARM, Thecus n4100) - to have a total of 800 GB storage, with some protection against a drive failure. As the machine is not very powerful, I don't want to use RAID-5 nor RAID-6. Previously, I would use RAID-0 on top of two RAID-1s: ----RAID0---- | | RAID1 RAID1 | | | | HDD1 HDD2 HDD3 HDD4 With RAID-0 on top of RAID-1, with 4 drives, I would achieve: - 100% chance of recovery if any single, one disk fails, - 50% chance of recovery if any two disks fail. Now with RAID-10 in the Linux kernel, what are my chances of recovering from a single and two disk failure? RAID10 ------------------ | | | | HDD1 HDD2 HDD3 HDD4 Is it also 100% if one disk fails, and 50% if two disks fail? Or perhaps, with 4 drives, RAID-10 can survive any 2 disks failure? -- Tomasz Chmielewski http://wpkg.org