On 27/08/2007, at 12:36 AM, Rainer J.H. Brandt wrote: > Sorry, this is a bit off-topic, but anyway: > > Ronald Kuehn writes: >> No. You can neither access ZFS nor UFS in that way. Only one >> host can mount the file system at the same time (read/write or >> read-only doesn't matter here). > > I can see why you wouldn't recommend trying this with UFS > (only one host knows which data has been committed to the disk), > but is it really impossible? > > I don't see why multiple UFS mounts wouldn't work, if only one > of them has write access. Can you elaborate?
Even with a single writer you would need to be concerned with read cache invalidation on the read-only hosts and (probably harder) ensuring that read hosts don't rely on half-written updates (since UFS doesn't do atomic on-disk updates). Even without explicit caching on the read-only hosts there is some "implicit caching" when, for example, a read host reads a directory entry and then uses that information to access a file. The file may have been unlinked in the meantime. This means that you need atomic reads, as well as writes. Boyd _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
