Date: Sun, 20 May 2007 22:55:47 -0500 From: Eric Anderson <anderson@freebsd.org> To: Gore Jarold <gore_jarold@yahoo.com> Cc: freebsd-fs@freebsd.org Subject: Re: dangers of delaying an fsck on busy fileserver ? Message-ID: <46511843.4010205@freebsd.org> In-Reply-To: <653845.99663.qm@web63012.mail.re1.yahoo.com> References: <653845.99663.qm@web63012.mail.re1.yahoo.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On 05/20/07 15:28, Gore Jarold wrote: > --- Scott Long <scottl@samsco.org> wrote: > >> Gore Jarold wrote: >>> --- Scott Long <scottl@samsco.org> wrote: >>> >>> >>>> In an ideal world, the only consequence of >> delaying >>>> bgfsck is that >>>> not all filesystem blocks will be marked free >> that >>>> should be. So >>>> if you deleted a large tree of files before the >>>> crash, those blocks >>>> might still show up in use until bgfsck >> completes. >>> >>> Thank you. Would _you_ do this with valuable data >> ? >> Very good question =-) If you're using softupdates >> then any >> damage will have been done when the hard shutdown >> happens; bgfsck >> won't create any new damage. The biggest problem of >> bgfsck beyond >> the i/o slowness and near deadlocks that it can >> create (modulo the >> fixes that the Kostik is working on) is that if it >> does encounter >> damage that it can't fix automatically, it exits and >> leaves the >> filesystem inconsistent. So you need to keep a very >> close eye on >> your logs and check for this, then schedule downtime >> when it happens >> so you can babysit a full fsck. > > > Ahhh... I think you may have misunderstood my original > question. What I am saying is, I don't _ever_ want to > do a background fsck. My systems are too busy (and > have too large of disks) to deal with the (current) > baggage of making a 4 TB snapshot and then > bg_fsck'ing. > > What I am saying is the following: > > - I set background_fsck_delay="86400" > > - I tell datacenter techs NOT to call me when the > system crashes - just to hit reset. > > - users bang on the system, as normal, for X hours - > all the while the filesystems are _dirty_ and nothing > is being done about it > > - I wake up hours later, unmount the filesystems, and > foreground fsck them > > My goal in all of this is to keep from being woken up > in the middle of the night. I don't care about the > downtime to the system when I eventually do foreground > fsck them, I just don't want to do it in the middle of > the night _and_ I don't want my users to have to sit > around waiting for me to do the fsck _on top of_ the > fsck downtime itself. > > So ... comments ? I _suspect_ the conclusions are > about the same - running on a dirty FS is the same as > running on a dirty FS while being bg_fsck'd ... but I > want to make sure... So can't you turn off background fsck, and set fsck_y_enable="YES"? That would allow your NOC to hit reset, and it'll come back and fsck in the foreground while you sleep. Eric
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?46511843.4010205>