Mark is right. This is one of the nice things about DCSS RO filesystems. Unlike disk, VM manages the space in such a way that the "owner" can go ahead and write new or changed content without worry of mixing up the "client" view of things. Very nice.
-- R; <>< On Wed, Aug 25, 2010 at 12:21, Mark Post <[email protected]> wrote: >>>> On 8/25/2010 at 08:26 AM, Christian Paro <[email protected]> wrote: >> As for ext2 vs ext3 for the read-only file system, there is a question of >> whether it's a disk which is to be written to once and then linked to and >> mounted read-only by everyone (in which case ext2 makes the most sense, with >> ext3 adding nothing but unnecessary overhead), or a disk which is regularly >> written to by one system - which you for some reason want be able to link to >> and mount read-only from another (in which case the ext3 journal does still >> serve a purpose while the disk is being accessed in write mode by that first >> system). > > This would be a very dangerous practice, and one I always tell people to > never use. If a file system is going to be shared between Linux systems, it > needs to be mounted read-only by all systems, including the "owner" of it. > (Unless we're talking about clustering file systems, which we're not.) Given > the way Linux delays write I/O you're likely to never have a consistent view > of the file system from anywhere other than the owner. Throw in z/VM > minidisk caching and the problem can get much worse very quickly. > > To me, the bottom lines is that if you want to share non-clustering file > systems, no one can have it mounted read-write. If that functionality is > necessary, then you need to go with a cluster file system and all the > additional infrastructure that entails. With SLES11 that was made pretty > easy to do, and SLES11 SP1 improves on that. The SLE High Availability > Extension is a no additional cost option for anyone with a valid SLES > subscription. Use it, and keep your data intact. > > > 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/
