Re: multiple device usage

Chris Samuel
2009-01-01T01:02:17Z

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On Wed, 31 Dec 2008 8:25:08 am Chris Mason wrote:

> This gets confusing in a hurry, but the idea is to duplicate metadata by
> default.  So, if you're using the default mount options on a single
> drive and add a second drive, it should switch metadata to raid1.

Yup, that's what I inferred from your earlier posts and the code. :-)

> I've always planned on adding an option to btrfs-vol -b to have it
> change the data or metadata allocation policies (raidX to raidY,
> restripe etc).  The kernel side code is all there, we just need
> something to wire it up to userland.

Understood. If I get some Copious Spare Time (tm) I might take a look at that
(though don't let that stop anyone else trying first!).

> data duplication on a single spindle could work, I just haven't hooked
> it up because I couldn't think of a really strong reason to do it ;)

I think for SSD's it could be really handy, especially for people who have a
standard distro install and decide they want to convert their ext3 partition
to btrfs using the tools. It's just a bit easier than getting them to
backup, repartition, make the filesystem and restore.

Downside of course is that those original blocks never get mirrored (unless
something like btrfsck was extended to fix those things up).

cheers,
Chris
--
Chris Samuel : http://www.csamuel.org/ : Melbourne, VIC

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