Date: Sun, 24 Jun 2012 09:34:43 -0700 From: Kevin Oberman <kob6558@gmail.com> To: "J. Hellenthal" <jhellenthal@dataix.net> Cc: Adam Vande More <amvandemore@gmail.com>, Greg Byshenk <freebsd@byshenk.net>, "freebsd-stable@freebsd.org" <freebsd-stable@freebsd.org>, "Leonardo M. Ram?" <martinrame@yahoo.com> Subject: Re: fsck_ufs running too often Message-ID: <CAN6yY1vVq7sB6uU%2BegsNRRXpoAciOcGprEnGF7SLiX0yYKia%2Bw@mail.gmail.com> In-Reply-To: <20120624160631.GA80121@DataIX.net> References: <1340401637.32116.YahooMailNeo@web113519.mail.gq1.yahoo.com> <3729A720-2C8F-4C84-B05A-201394C40D63@gothic.net.au> <20120624013624.GG24842@portland1.byshenk.net> <20120624025451.GA17721@DataIX.net> <CA%2BtpaK2q_9=cp6tQ__H9U9UDvbvmocF3sgc7jx_yYjRqALv01A@mail.gmail.com> <20120624160631.GA80121@DataIX.net>
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On Sun, Jun 24, 2012 at 9:06 AM, J. Hellenthal <jhellenthal@dataix.net> wrote: > > > On Sat, Jun 23, 2012 at 10:15:19PM -0500, Adam Vande More wrote: >> On Sat, Jun 23, 2012 at 9:54 PM, Jason Hellenthal <jhellenthal@dataix.net>wrote: >> > >> > At one point it was proven that background fsck was not benefitial. >> >> >> Where can we find this "proof"? >> > > It was in the lists amongst many conversations. I think the term 'proof' is being abused here. Proof is rigorous, demonstrable and precise. It is not a non-specific coalescence of bit and pieces in a mail thread. My experience with background fsck is that its benefit is entirely dependent on the requirements of the system. A few things are entirely clear and easily demonstrated. (Note, this is an assertion and not proof.) 1. Background fsck takes considerably longer to run than fsck 2. fsck places a very substantial I/O load on the system, primarily on the disk undergoing the check 3. Other system activity that requires I/O to the disk being checked will slow 4. Background fsck is limited and, when it cannot correct some problems can impact system stability, especially in the event of power failure 5. For systems with large file systems it will make the system available for use MUCH sooner than would be the case if a standard fsck was used As with almost all system performance issues, background fsck requires looking at its benefits and costs. For some, it is a big win. For others it is a losing proposition because a server is rendered effectively useless for an extended period. Full disclosure: I have disabled background fsck on most of the systems for which I am responsible, but not all. -- R. Kevin Oberman, Network Engineer E-mail: kob6558@gmail.com
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