From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Dake Subject: Re: readonly start of Linux RAID Date: Wed, 29 Jan 2003 09:53:39 -0700 Sender: linux-raid-owner@vger.kernel.org Message-ID: <3E380713.7090709@mvista.com> References: <3E36C2C3.3070101@shaolinmicro.com> <3E36CBB5.6050904@mvista.com> <3E37445F.5020609@shaolinmicro.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <3E37445F.5020609@shaolinmicro.com> To: David Chow Cc: neilb@cse.unsw.edu.au, linux-raid@vger.kernel.org List-Id: linux-raid.ids David, The changes to the md driver itself are minimal to support clustering and I think they are likely to make kernel.org (the ability to set read-only or write mode with some extensions to support resyncs between cluster nodes). The significant changes are to the userland utilities. I also have an implementation of raid multihost locking, which locks a RAID array to a specific host ID (based upon geographical address, fibrechannel host's wwn, or scsi host id). This ensures that a RAID cannot be shared between hosts and will prevent other hosts from starting the raid or causing any problems with it. Regards, -steve David Chow wrote: > Steve, > > Thanks for replying. The message you given talked about a cluster > implemetation of MD driver which is completely out of the scope of > linux raid. I do think such implementation belongs to some cluster > file system or volume management systems, and it seems such > implementation of md will be very hard to get into the stock kernel . > What I am asking is a generic simple enhancement of the md which might > be useful in lot of areas (shared storage is just one example), and > even administration on preventing some md being rebuild immediate > after an unclean shutdown or similar senarios. The work to do is > mimimal comparing the work on a cluster md driver implementation. > > Someone talk about this... > http://marc.theaimsgroup.com/?l=linux-raid&m=103300356601897&w=2 > > Neil talked about this before too... > http://marc.theaimsgroup.com/?l=linux-raid&m=102669565104333&w=2 > > Please give pointer to access information so that I can keep track the > read-only stuff if it exists. Thanks. > > regards, > David > > Steven Dake wrote: > >> David, >> >> Read this regarding enhancing the MD driver to work in a shared >> storage environment. >> >> http://marc.theaimsgroup.com/?l=linux-raid&m=104170749423143&w=2 >> >> David Chow wrote: >> >>> Hi Neil, >>> >>> I've been reading some archives in the Linux RAID mailing list. >>> Someone ask for implementing a readonly mode instead of degraded >>> mode in RAID-1/5 setups. I'm falling into a similar problem . I >>> think it is important to have a readonly mode on starting a RAID >>> device or operating on a RAID device. Think of systems that didn't >>> want to rebuild their RAID immediately after an unclean shutdown... >>> Calling autorun() ioctls will make all devices starting rebuild >>> themselves in case of any available disk exists. In case we are on a >>> shared storage system, the active cluster might have using the RAID >>> disks which seems to be unclean on the other standby cluster. The >>> standby cluster might want to have a read-only inspection of the >>> shared storage. In case of a high availability cluster system >>> failover, the standby cluster might want to determine to start full >>> read/write access by some tools instead of forced automatic at >>> system boot (initrd calling raidautorun). In such circumstances, the >>> curr! >>> ! >>> ent md driver cannot be used. This also prohibits many >>> implementation of a high availability system from implement linux >>> RAID on a shared storage on an HA system which is extremely >>> important. I guess, this problem also comes with LVM and other >>> similar volume management system. I'm currently studying the md.c >>> code in a 2.4.19 kernel which I see implementing a read-only mode >>> for md is possible. Please give advice or anything happening, so >>> that I don't spend duplicated efforts. Thanks. >>> >>> >>> regards, >>> David Chow >>> >>> > > >