Clayton Wheeler wrote:
I'm setting up OpenSolaris on Amazon EC2, and planning on using their Elastic Block Store volumes to store a persistent ZFS zpool. I'm inclined to make a mirror of two EBS volumes (essentially LUNs with snapshot features and an API for mapping/unmapping them), for better data protection. However, EC2 only lets you snapshot one volume at a time; there is no consistency group feature for taking simultaneous snapshots of the volumes comprising a zpool. Likewise, you can only map or unmap one volume at a time.
Interesting. Let us know how it works.
My question is this: how well can ZFS deal with the mirror devices getting out of sync? For instance, if one or both of my EBS volumes are lost and I have to restore from EBS snapshots, one volume will have a newer version of the data than the other. Will ZFS be able to recognize this and safely resilver from the newer device to the older?
Syncing is done to a transaction group. By default, txgs are sync'ed every 5 or 30 seconds. It would be relatively easy to setup a script which would notify EBS to snap immediately after a txg commit completes. If the workload contains a lot of sync writes, special care would be needed to design the system to properly deal with the ZIL. -- richard _______________________________________________ zfs-discuss mailing list [email protected] http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
