Hey folks, Does anybody know if any of these are on the roadmap for ZFS, or have any idea how long it's likely to be before we see them (we're in no rush - late 2008 would be fine with us, but it would be nice to know they're being worked on)?
I've seen many people ask for the ability to expand a raid-z pool by adding devices. I'm wondering if it would be useful to work on a defrag / restriping tool to work hand in hand with this. I'm assuming that when the functionality is available, adding a disk to a raid-z set will mean the existing data stays put, and new data is written across a wider stripe. That's great for performance for new data, but not so good for the existing files. Another problem is that you can't guarantee how much space will be added. That will have to be calculated based on how much data you already have. ie: If you have a simple raid-z of five 500GB drives, you would expect adding another drive to add 500GB of space. However, if your pool is half full, you can only make use of 250GB of space, the other 250GB is going to be wasted. What I would propose to solve this is to implement a defrag / restripe utility as part of the raid-z upgrade process, making it a three step process: - New drive added to raid-z pool - Defrag tool begins restriping and defragmenting old data - Once restripe complete, pool reports the additional free space There are some limitations to this. You would maybe want to advise that expanding a raid-z pool should only be done with a reasonable amount of free disk space, and that it may take some time. It may also be beneficial to add the ability to add multiple disks in one go. However, if it works it would seem to add several benefits: - Raid-z pools can be expanded - ZFS gains a defrag tool - ZFS gains a restriping tool This message posted from opensolaris.org _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
