From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steve Costaras Subject: mdadm / force parity checking of blocks on all reads? Date: Thu, 17 Feb 2011 20:04:48 -0600 Message-ID: <4D5DD3C0.3020804@chaven.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; 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'm looking at alternatives to ZFS since it still has some time to go for large scale deployment as a kernel-level file system (and brtfs has years to go). I am running into problems with silent data corruption with large deployments of disks. Currently no hardware raid vendor supports T10 DIF (which even if supported would only work w/ SAS/FC drives anyway) nor does read parity checking. I am hoping that either there is a way that I don't know of to enable mdadm to read the data plus p+q parity blocks for every request and compare them for accuracy (simlar to what you need to do for a scrub but /ALWAYS/) or have the functionality added as an option. With the current large capacity drives we have today getting bit errors is quite common (I have some scripts that I do complete file checks every two weeks across 50TB arrays and come up with errros every month). I'm looking at expanding to 200-300TB volumes shortly so the problem will only get that much more frequent. Being able to check the data against parity will be able to find/notify and correct errors at read time before they get to user space. This fixes bit rot as well as torn/wild reads/writes and mitigates transmission issues. I searched the list but couldn't find this benig discussed before, is this possible? Steve Costaras stevecs@chaven.com