From mboxrd@z Thu Jan 1 00:00:00 1970 From: Spelic Subject: Does multipath require disabled write cache? Date: Sun, 20 Jul 2014 23:20:07 +0200 Message-ID: <53CC3287.3010708@shiftmail.org> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: device-mapper development List-Id: dm-devel.ids Hello all, I am wondering if multipath requires a disabled write cache at the remote disks. We have some external SAS disks, for which the connection is flaky and sometimes is lost and then they are detected again. Multipath seems perfect for this situation. However, when the disks are lost, I suppose resets are issued, which might clear the write cache so that data located there might not be committed (true? well at least on power loss this is true). It would be great if multipath would issue a flush every N writes, and then remember the last N writes and resubmit them when the path is reestablished, so that there is again chance to flush them to stable storage. (similar to DRBD epochs) However I don't know if this smart mechanism is implemented. Thanks for info S.