From mboxrd@z Thu Jan 1 00:00:00 1970 From: Takahiro Yasui Subject: Re: DM-RAID1 data corruption Date: Thu, 25 Jun 2009 12:16:24 -0400 Message-ID: <4A43A2D8.6030709@redhat.com> References: <20090415031210.GA11881@us.ibm.com> <49E645DA.4010204@redhat.com> <20090416024959.GB19876@us.ibm.com> <49E7B029.20906@redhat.com> <20090623010930.GA13392@us.ibm.com> <4A41065D.10804@redhat.com> <19009.38782.225681.85214@notabene.brown> <4A424FC3.50809@redhat.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Mikulas Patocka Cc: device-mapper development List-Id: dm-devel.ids On 06/25/09 10:47, Mikulas Patocka wrote: >> superblock approach may solve this data corruption issue without an >> additional delay. When dm-raid1 detects a write error, it can disable >> the mirror leg quickly and ask userspace to process aftertreatment. >> >> I would like to continue discussion how to fix this issue. >> >> Thanks, >> Taka > > The current code already blocks all i/os if the log fails. So if your > application is sensitive for it, you have to test for it anyway. It is also a known issue. We are trying to make a log device redundant to prevent disk replication when a log device has problem. It will solve the delay caused by a log device failure as well. > You can write new implementation dm-raid1.2 that will have two log devices > (just like md-raid has two superblocks) and can perform without userspace > intervention if any of the legs or logs fail. > > But it is really more like rewrite --- I think it would be easier to write > it from scratch than to patch it over existing dm-raid1 code. Hmm. I will look at implementation if we could add superblocks into current code. Thanks, Taka