On 8/4/2010 10:10 AM, Emmanuel Noobadmin wrote:
derivative work or something along those lines.
the OpenSolaris or NexentaStor versions since you wouldn't be using much else from the system anyway.
If I really have to, but I was hoping I wouldn't need to learn another relatively similar OS and get myself confused and do something catastrophic while in console one day. Especially since I'm way behind schedule on picking up another programming language for projects my boss wants me to evaluate.
That's sort of the point of nexentastor which gives you a web interface to manage the filesystems and sharing since you don't need anything else. But the free community edition only goes to 12 TB. That might be enough per-host if you are going to layer something else on top, though.
Snapshots and block-level de-dup are other features of zfs - but I think you'll lose that if you wrap anything else over it. Maybe you could overcommit an iscsi export expecting the de-dup to make up the size difference and use that as a block level component of something else.
Honestly, I've no idea what all that was about until I go read them up later although I understand vaguely from past reading that snapshot is like a backup copy
It is good for 2 things - you can snapshot for local 'back-in-time' copies without using extra space, and you can do incremental dump/restores from local to remote snapshots.
However, in my ideal configuration, when a VM host server dies, I just want to be able to start a new VM instance on a surviving machine using the correct VM image/disk file on the network storage and resume full functionality.
The VM host side is simple enough if its disk image is intact. But, if you want to survive a disk server failure you need to have that replicated which seems like your main problem.
Since bulk of the actual changes is to "files" in the virtual disk file, having snapshot capabilities on the underlying fs doesn't seem to be useful. ZFS checksum ensuring that all sectors/inodes of that image file are error free seems more critical. Please do point out if I am mistaken though!
If you can tolerate a 'slightly behind' backup copy, you could probably build it on top of zfs snapshot send/receive replication. Nexenta has some sort of high-availability synchronous replication in their commercial product but I don't know the license terms. The part I wonder about in all of these schemes is how long it takes to recover when the mirroring is broken. Even with local md mirrors I find it takes most of a day even with < 1Tb drives with other operations becoming impractically slow.