The server that has it in rw mode can write new data at any time. Thus reorganize datablocks inodes and whatever needed to fit the new files into free space. The other server may not be aware of this move of bytes on the disk. So an IO error might happen, or maybe read-error, don't know which.
_________________________________________________ Tore Agblad System programmer, Volvo IT certified IT Architect Volvo Information Technology Infrastructure Mainframe Design & Development, Linux servers Dept 4352 DA1S SE-405 08, Gothenburg Sweden Telephone: +46-31-3233569 E-mail: [email protected] http://www.volvo.com/volvoit/global/en-gb/ -----Original Message----- From: Linux on 390 Port [mailto:[email protected]] On Behalf Of Roger Evans Sent: den 12 oktober 2011 09:44 To: [email protected] Subject: Re: dasd_configure doesn't see partition 1 on RO disk I've been using this scenario for database backups since we had the discussion about shared VM disks on this thread about a year ago. David made the point then that if you had a hipervisor that allowed it, not making a disk dependent on one of the machines being up at all times (as with NFS), had some advantages.. I also used Tore's suggestion to stick to ext2 so nobody would try to replay a journal. .I use them for database backups that I take each night, and for SLES10 (both SP1 and SP3) it works fine. IF the RW linux is down (usually because it didn't come up again), caching won't be an issue. If the machine that 'owns' the database/disk is down, I can still see the database, and can recover a copy on the machine that has RO access. without having to go in and change the VM configuration. It's also easy to check to see that the backup went ok. and the recovery would work. I haven't tried sharing a disk between 2 SLES 11 machines yet, and that's where I'm going with upgrades. If it doesn't work, it would be nice to know. Why would the fact that one of the machines has the disk mounted RW keep the other(s) from seeing it at all? Best Regards/ Med vennlig hilsen Roger Evans ________________________________________________________________________ On Tue, 2011-10-11 at 10:11 -0600, Mark Post wrote: > >>> On 10/11/2011 at 04:26 AM, Roger Evans <[email protected]> wrote: > > I am trying to mount a disk R/O from two linux machines on one VM. One > > of them is SLES10 where the disk is defined in zipl.conf. The other > > is a new SLES11 ('CLPRODB2).. > > > > The disk is mounted RW on a SLES10sp3 machine. > > This is never a good idea. If you want to share a disk between z/VM guests, > _all_ of them need to have it read only. None of them can have it > read-write. There's too many layers of caching going on for it to work > reliably, if at all. > > If you absolutely have to have access to a disk that is mounted read-write, > use NFS to export it read only. > > > Mark Post > > ---------------------------------------------------------------------- > For LINUX-390 subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO LINUX-390 or visit > http://www.marist.edu/htbin/wlvindex?LINUX-390 > ---------------------------------------------------------------------- > For more information on Linux on System z, visit > http://wiki.linuxvm.org/ ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/ ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
