Date: Thu, 10 Jul 2008 21:23:58 +0200 From: Ivan Voras <ivoras@freebsd.org> To: freebsd-fs@freebsd.org Subject: Re: Storing UFS snapshots externally? Message-ID: <g55nkh$cgf$1@ger.gmane.org> In-Reply-To: <48765802.9060502@audilis.com> References: <48765802.9060502@audilis.com>
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[-- Attachment #1 --] Daniel E. Lynn wrote: > Greetings all, > > First, let me apologize if this has been asked before. If it has then my > search skills must be lacking because I couldn't seem to find it in the > lists anywhere. > > I'm wondering if it is feasible to store snapshots for UFS on a separate > drive, and if so if there is an advisable way of doing it. The basic > idea is that I'd like to be able to mitigate any write overhead of using > a lot of snapshots by using a separate disk for them entirely. Here's > the proposed setup: > > FreeBSD (/) is on ad0 > Homedirs and userdata (/data) is on gm0 (ad2+ad3 mirrored) > > I've been successfully using snapshots for /data, and the overhead on > this system doesn't seem too bad (yet) but if I have more than a dozen > snapshots, I get the feeling it could get messy. It'd be great if I > could store the snapshots for /data on / someplace. UFS snapshots don't copy the data into the "snapshot" file - they just adjust internal references in the file system. The big file you get when you create the snapshot isn't really a file in the traditional sense - it consists of file system internal pointers to real data. Simplified, when data gets changed on the "real" file system, *then* the old data gets a separate copy in the snapshot. In short, there's no way other than manually copying (dd, tar) the data from the snapshot to wherever. [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.5 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFIdmHPldnAQVacBcgRAhNvAJ4rsx9g2HQkPxU1qy3O3sH0dWkcewCdERdv N4TwMdwkouvPmlfwrC2Y18k= =OGUV -----END PGP SIGNATURE-----
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