From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gandalf Corvotempesta Subject: Re: New setup: partitions or raw devices Date: Sat, 2 Dec 2017 14:14:07 +0100 Message-ID: <6066a947-2a4e-d8d5-239d-dccb80e39ac0@gmail.com> References: <7f6abcbc-7dfa-0252-e9df-984e7e637936@thelounge.net> <3654cb70-9d7c-dfc0-f57d-c57004f11f92@thelounge.net> <253c22a2-8f77-2737-b3b4-6beef107c28c@youngman.org.uk> <14078b47-29dd-6c07-f680-77ac9445be32@thelounge.net> <87tvxazahs.fsf@esperi.org.uk> <5A218EDB.6030909@youngman.org.uk> <1d3830e8-9e5e-681c-d556-1b8b6524dda2@thelounge.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1d3830e8-9e5e-681c-d556-1b8b6524dda2@thelounge.net> Content-Language: en-US Sender: linux-raid-owner@vger.kernel.org To: Reindl Harald , Wols Lists , Nix Cc: Linux RAID Mailing List List-Id: linux-raid.ids Il 02/12/2017 00:44, Reindl Harald ha scritto: > a RAID10 can survive two faile disks while a RAID5 is for sure dead Absolutely not. This is a common misconception. RAID-10 can survive two failed disks IF AND ONLY IF these disks are on different mirrors. I had multiple (more than 4) RAID-10s totally lost due to double failure in the same mirror. Each disk in a mirror will get the same write pattern, thus, you'll risk a double failure for any firmware bugs or similiar. With SSDs this risk is higher, because you wear out both members in the same way at the same time. If the controller kicks out two adiacent disks, you'll loose everything (this is happened to me: fully synced RAID10: disk0 was kicked out by the controller, RAID survived and after a couple of minutes, disk0 was automatically reactivated and started a rebuild. during the rebuild, disk1 was kicked out. RAID lost: disk0 out-of-sync and disk1 kicked out) RAID-6 is *much* more safe than RAID-1/RAID-10 as it can survive ANY TWO disks failure, you will loose data on the third failure.