From mboxrd@z Thu Jan 1 00:00:00 1970 From: malahal@us.ibm.com Subject: Re: [RFC][PATCH 0/4] dm-log: support multi-log devices Date: Mon, 5 Jan 2009 10:44:08 -0800 Message-ID: <20090105184408.GA20412@us.ibm.com> References: <492C91DF.7040507@redhat.com> <49467039.6060801@redhat.com> <20081220001305.GA8574@us.ibm.com> <49502F7E.9040300@redhat.com> <20081223180228.GA24831@us.ibm.com> <49622ADB.7040200@redhat.com> <20090105162435.GB18452@us.ibm.com> <4962450C.20507@redhat.com> Reply-To: device-mapper development Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <4962450C.20507@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: dm-devel-bounces@redhat.com Errors-To: dm-devel-bounces@redhat.com To: Takahiro Yasui Cc: dm-devel@redhat.com, agk@redhat.com List-Id: dm-devel.ids Takahiro Yasui [tyasui@redhat.com] wrote: > > Not really. What I meant is re-integrating a failed log device when it > > comes back again. That is also what I mean by handling 'transient > > errors'. > > Thanks, I see your requirement on this feature. > Let me put one more question. > > LVM mirroring is used to make system available even if some devices, > such as data and log device, have a problem. Currently, activations > by "vgchange -ay" command seem to fail during system booting if one > of devices related to VG are missing or had I/O error. For example, > if a mirror is structured by two data devices and log devices, the > mirror logical device should be activated and used even if one data > device and one log device are missing. > > Could you give me an idea or solution to handle this? Do we need to > enhance your feature to achieve this requirement? The requirement you are asking is more than "mirrored log" support. Actually it is nothing to do with "mirrored log" support! LVM has "--partial' option but that creates read-only volumes. IBM has implemented "--partial-rw" that activates such mirror devices. Essentially it creates an 'error device' in place of a missing device, but the patch isn't complete as it doesn't work well with other segment (target) types! What we need is changes to LVM "--partial" code path where it can create volumes read-only or read-write based on what is available instead of blindly doing read-only. Thank you for looking at these enterprise level features. Thanks, Malahal.