Date: Tue, 16 Jan 2007 15:37:39 -0500 From: Kris Kennaway <kris@obsecurity.org> To: Willem Jan Withagen <wjw@withagen.nl> Cc: freebsd-stable@freebsd.org, Scott Oertel <freebsd@scottevil.com>, Willem Jan Withagen <wjw@digiware.nl>, Kris Kennaway <kris@obsecurity.org> Subject: Re: running mksnap_ffs Message-ID: <20070116203739.GA343@xor.obsecurity.org> In-Reply-To: <45AD3507.402@withagen.nl> References: <200701161934.l0GJY1mh057095@ambrisko.com> <45AD3507.402@withagen.nl>
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--0OAP2g/MAC+5xKAE Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Jan 16, 2007 at 09:26:47PM +0100, Willem Jan Withagen wrote: > Doug Ambrisko wrote: > >| > or things can get wedged. We have some other patches as well that= =20 > >might > >| > be required. As a hack on a local server we have been using snap sh= ots > >| > to do a "hot" back-up of a data base each morning. This is based on > >| > 6.x. > >| > >| What do you mean by "get wedged"? Are you seeing a deadlock, and if > >| so then what are the details? When you say 6.x, do you mean > >| up-to-date RELENG_6? There were various snapshot deadlock fixes > >| committed over the past year including some in the past few months. > > > >The file-system would come to a stop, processes stuck on bio, snap-shots > >not finishing etc. This was caused by the system running out of usable > >buffers. The change forces them to be flushed every so often. This is > >independant of locking. 10 might be to aggresive. Some scaling of > >nbuf would probably be better. >=20 > When I run mksnap_ffs it runs to the point where ANY access to the=20 > filesystem gives that process a lockup. Yes, that is expected. Actually it begins when something accesses the directory in which the snapshot is being made, since that causes the parent directory to be locked...then something tries to access the parent directory, which eventually cascades back to the root. > Getting the file system back is only thru "hard reboot". Trying to do it= =20 > the gentle way locks the whole system. Or waiting until the snapshot operation finishes. You (still) haven't determined that it's actually hanging as opposed to just waiting for the snapshot operation to finish. Kris --0OAP2g/MAC+5xKAE Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (FreeBSD) iD8DBQFFrTeSWry0BWjoQKURAp0VAJ4ya2IuNGi6Ko5UkzG6fmXBhPtR+wCgrxRD OxdTYM2KMvMIazTyfhNzsrE= =cCcA -----END PGP SIGNATURE----- --0OAP2g/MAC+5xKAE--
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