From mboxrd@z Thu Jan 1 00:00:00 1970 From: Reindl Harald Subject: RAID10 and 'writemostly' support Date: Thu, 16 Feb 2017 15:08:32 +0100 Message-ID: <07e8d394-2f95-caae-d971-a5fef009fefe@thelounge.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; 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 Hi i am new and was redirected to this list from the bugtracker please have a look at https://bugzilla.kernel.org/show_bug.cgi?id=194551 currently "writemostly" seems to be only supported on "real" RAID1 while i was in hope that by the conecpt of RAID10 having more or less RAID0+RAID1 it would also work on RAID10 (and on the virtual machine wre i tested mdadm with the flag before buying the disks it did not complain) RAID10 with "writemostly" makes a lot of sense for large storages to get them fast *and* reliable without make it extremly expensive * you don't want RAID5/RAID6 rebuild over many TB * very large SSD for RAID1 are much more expensive than smaller ones so with 4x2 TB disks you get 4 TB useable storage and with "writemostly" which would be in the best case "writeonly" you have a lightening fast RAID0 on SSD with good redundancy most workloads are read-intense with less writes (rsync with --checksum enabled, booting, starting large applications...) another benefit: different technologies - it's very unlikely that both disks of a stripe fail at the same time or due rebuild when one half is a SSD and the other a HDD