Hi Henrik Yes I have the following concerns….. and as I haven’t done any practical tests this is only “in theory”….
1. Reclaiming thin devices will not work, EMC have a 768K byte minimum reclaim limit (768Kbytes needs to be all zeros). And HDS have 42MB I believe, IBM and 3PAR I don’t know. The COW will eventually leav footprints in ~128Kbytes and as that is less then eg: 768 it will be difficult to reclaim that space. 2. ZFS don’t have the possibility to “tell the array” to reclaim it’s blocks, and event is ZFS would be able to do that in the future how will 8-128Kbytes harmonize with the 786Kbytes for EMC and 42MB for HDS? 3. I have concerns of the COW behavior, Will this create a “random read” situation for the spindles “in my 450TB array”. 4. COW don’t have any performance advantages when the IO arrives at the storage arrays as writes always is written to the cache (if it’s not full). 5. We are an EMC V-MAX customer that have decided to only use thin devices, one reason is that we plan to use FAST VP in the future with SSD FC and SATA disk installed in the array. My belief is that in a ZFS + thin device environment this feature will not have the possibility to interact with the (future) FAST VP algorithm as the COW will spread it’s blocks in a non predictable way. 6. The cost savings will not be sufficient when comparing ZFS free of charge with VxFS thin aware in our environment as the over allocation in the file systems are significant. 7. The possibility to over provision a server when thin devices work 100% can be administratively positive as the organization don’t need to spend time with provisioning “as often” in a thin aware configuration as the real disk is not consumed. 8. We don’t use this but I would like to have a ”backup mount server” dealing with our major large Oracle databases, I believe that snapshots of an ZFS file system can’t be exported outside the server. Ps: I do understand that ZFS will make th administration easyer from a Solaris perspective /Laban -- This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
