Date: Wed, 24 May 2006 07:18:00 -0500 From: Eric Anderson <anderson@centtech.com> To: Kris Kennaway <kris@obsecurity.org> Cc: freebsd-fs@freebsd.org Subject: Re: Access to UFS stuck during snapshot. Message-ID: <44744EF8.2000000@centtech.com> In-Reply-To: <20060524061848.GA58522@xor.obsecurity.org> References: <4473FA8F.6050102@outblaze.com> <20060524061848.GA58522@xor.obsecurity.org>
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Kris Kennaway wrote: > On Wed, May 24, 2006 at 02:17:51PM +0800, Kent Ho wrote: >> Hi, >> >> I having problems accessing file system during snapshot runs. snapshot >> takes approximately 10 to 20 mins to run. >> >> During that time access to files in the file system are blocked until >> the snapshot has completed. Lot of processes was stuck and piles up on >> the fs. >> >> This fs stores mailboxes and it's accessed 24/7. This is similar to >> what described in this thread. >> >> http://www.freebsd.org/cgi/getmsg.cgi?fetch=14968+0+/usr/local/www/db/text/2006/freebsd-fs/20060312.freebsd-fs >> >> Has this been improved or fixed in recent releases, I see a bunch of >> fixes in march? any possible work around? any alternatives or >> recommendations? Looking for high availability fs with snapshots. > > It's by design. > > Kris I found that making the .snap directories permissions 0700, and then making a subdirectory under the .snap that stores the actual snapshots helped, as long as I did not make any stat() calls to the snapshot file that was in snaplk state. Kris - you've had your head deep in the snapshot spaghetti recently - is this blocking just a matter of the locking on the snapshot file and a stat() call blocking on it, which causes an upward locking to the root dir of the filesystem? Could this be avoided by 'hiding' the snapshot file while a snapshot is in progress? I have been tinkering with hiding the snapshot directory during snapshot creation, but I don't have any results of anything yet, still too early. I'm a wannabe hacker, so my progress is slow. Eric -- ------------------------------------------------------------------------ Eric Anderson Sr. Systems Administrator Centaur Technology Anything that works is better than anything that doesn't. ------------------------------------------------------------------------
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