On Sun, Feb 01, 2009 at 04:26:13PM -0600, Gary Mills wrote: > I realize that this configuration is not supported. What's required
It would be silly for ZFS to support zvols as iSCSI LUNs and then say "you can put anything but ZFS on them." I'm pretty sure there's no such restriction. (That said, I can't speak for the ZFS team, and it's remotely imaginable -barely- that there could be such a limitation, but it would be strange indeed.) > to make it work? Consider a file server running ZFS that exports a > volume with Iscsi. Consider also an application server that imports > the LUN with Iscsi and runs a ZFS filesystem on that LUN. All of the > redundancy and disk management takes place on the file server, but > end-to-end error detection takes place on the application server. > This is a reasonable configuration, is it not? IMO it's no more and no less reasonable than putting a DB on an iSCSI LUN backed by ZFS. > When the application server detects a checksum error, what information > does it have to return to the file server so that it can correct the > error? The file server could then retry the read from its redundant > source, which might be a mirror or might be synthentic data from > RAID-5. It might also indicate that a disk must be replaced. ZFS relies on doing all the mirroring and/or RAID-Z work itself in order to be able to recover from bad blocks. If you put the redundancy below ZFS (e.g., using HW RAID) then you typically lose that capability, BUT with ZFS on the target side the target-side ZFS will be able to do the recovery while still retaining end-to-end integrity protection. Neat, eh? > Must any information accompany each block of data sent to the > application server so that the file server can identify the source > of the data in the event of an error? In this case there's no need: the target will know which blocks are bad and automatically correct (assuming enough redundancy exists). Nico -- _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
