[BBLISA] filesystems supporting snapshots

[Daniel Feenberg]

On Wed, 22 Aug 2007, Adam Moskowitz wrote:

> Tom Metro <tmetro+bblisa at vl.com> wrote:
>> I've also wondered, given the value of that feature, why we haven't seen
>> it appear in one of the community developed, open source file systems.
>
> I'm pretty sure Kirk McKusick out snapshots in the FreeBSD FFS quite a
> few years ago. I suspect it never really took off because of the
> relative populatiries of FreeBSD v. Linux.

We have had experience with FreeBSD snapshots, and found that taking a 
snapshot took much longer than doing an fsck, typically several hours on 
our larger (1 TB) partitions. This surprised us, since Mr McKusick wrote 
that snapshots should take seconds. We found several other users had 
posted similar times to ours, with no contradictory replies. We had to 
conclude that FreeBSD snapshots are not usable, or that we were doing 
something wrong. We still put most of our non-Netapp storage on FreeBSD, 
but snapshots would be great. I wouldn't assume that snapshots are a 
side-effect of WAFL - they may be the main point of WAFL.

I posted a summary of our storage experiences at

    http://www.nber.org/sys-admin/linux-nas-raid.html

Daniel Feenberg


>
> AdamM
>
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