Date: Tue, 21 Mar 2006 13:41:27 -0500 From: Kris Kennaway <kris@obsecurity.org> To: John Kozubik <john@kozubik.com> Cc: freebsd-fs@freebsd.org, jroberson@chesapeake.net, freebsd-current@freebsd.org, tegge@freebsd.org, kris@obsecurity.org Subject: Re: UFS2 Snapshots in 6.1-Beta4 - Confirmed Problems Message-ID: <20060321184127.GA19204@xor.obsecurity.org> In-Reply-To: <20060320224313.O55763@kozubik.com> References: <20060320224313.O55763@kozubik.com>
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--J2SCkAp4GZ/dPZZf Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Mar 21, 2006 at 01:36:44AM -0800, John Kozubik wrote: > Here is the behavior I have witnessed: >=20 >=20 > First, I have confirmed that a filesystem with multiple snapshots that > undergoes multiple, rapid deletions of files, will cause the system to > hang. I have witnessed this before, but had not confirmed it or > documented it in a PR. Now that I have confirmed this behavior, I have > documented it in: kern/94769 >=20 > This is a serious problem because, in addition to making it nearly > impossible to run a system with multiple snapshots, it is conceivable that > enough rapid file deletions could occur on an otherwise non snapshotted > system that has a single snapshot on it due to a background fsck, to cause > the system to hang. > Second, kern/92292 is still a problem. I have reproduced this error in > 6.1-BETA4 (and have seen it happening since 5.1). The (small) difference > is that the cp process seems to stick in the flswai state instead of > biowr. Thanks, I'll try to reproduce these two. > This next one is complicated, and I haven't submitted a PR for it yet, but > I believe it is quite serious for reasons I will expand on below. >=20 > The problem is: If you completely fill a filesystem (109% usage in `df` > on most systems) that has a snapshot on it, the system becomes very > unresponsive - all interactive and disk response lags terribly and, > although the system is not hung, it is in many cases unusable. Yes :-( This will probably not be fixable in time for 6.1, but hopefully it will be addressed in the future. FYI, the system may also panic in this situation. Kris --J2SCkAp4GZ/dPZZf Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2.2 (FreeBSD) iD8DBQFEIEjWWry0BWjoQKURAhsiAJ9hM3S6oc9mSZmlT+/ArqJIrv8oGgCgsDkQ 5Vh0MycEjF/FC8O7VT9IXL8= =RopU -----END PGP SIGNATURE----- --J2SCkAp4GZ/dPZZf--
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