From owner-freebsd-questions Sun Apr 14 12:25:47 2002 Delivered-To: freebsd-questions@freebsd.org Received: from relay.pair.com (relay1.pair.com [209.68.1.20]) by hub.freebsd.org (Postfix) with SMTP id 6B4DB37B404 for ; Sun, 14 Apr 2002 12:25:38 -0700 (PDT) Received: (qmail 12702 invoked from network); 14 Apr 2002 19:25:37 -0000 Received: from rrcs-nys-24-97-1-162.biz.rr.com (HELO GPC) (24.97.1.162) by relay1.pair.com with SMTP; 14 Apr 2002 19:25:37 -0000 X-pair-Authenticated: 24.97.1.162 Message-ID: <00cc01c1e3ea$03382c70$9865fea9@GPC> From: "Gregory Keefe" To: "Fernando Gleiser" Cc: References: <20020414122514.E5464-100000@cactus.fi.uba.ar> Subject: Re: Softupdates Date: Sun, 14 Apr 2002 15:24:33 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00C9_01C1E3C8.7A9F5030" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG This is a multi-part message in MIME format. ------=_NextPart_000_00C9_01C1E3C8.7A9F5030 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable > > FreeBSD Claim: > > http://www.freebsd.org/features.html > > Soft Updates allows improved file system performance without = sacrificing > > safety and reliability > > > > A Unix Expert's Claim: > > http://cr.yp.to/qmail/faq/reliability.html > > ``Do not use async or softupdates filesystems. If you do, and if = your system > > crashes at the wrong moment, you will lose [data].'' > > Sofupdates ensure that the *filesystem* is not corrupt after a crash. > They don't say anything about *data*. You may lose data after a crash. > If you are worried about losing data, you can mount the filesystems > sync, but I don't think you'll like the performance. =3D0) I suspect the world widely acknowledges FreeBSD as a strong server = platform, at least more so than as a strong workstation platform (I use = it for one of my workstations, but at work everybody uses Windows). If = you accept that premise, then does it follow that the default install of = FreeBSD should be geared toward a server instead of a workstation? As a = server, what are its most common deployment scenarios? Web servers & = mail servers? Under a standard web or mail server setup, is the disk = I/O the most likely bottleneck? If so, then I suspect leaving = softupdates turned on by default is reasonable. If the bottleneck is = something else (bandwidth, or perhaps even no bottleneck at all under = most setups), then does it not make sense to offer the most reliability = that's possible, at least by default? Looking at DJB's claim again up top, I suspect that he desires his = software to really "mean it" when it responds to a client saying it = successfully received mail. And the best definition of "mean it" in = this context is that the mail is safely written to disk (I'd personally = go a step further and have it safely written to a cluster of servers' = disks, but that's certainly not reasonable for most environments). If = softupdates indeed compromises that feature, though, then couldn't a = faint shadow of doubt be cast over the reliability of the entire default = install? > IMHO, filesystem corruption is far worse than data loss of the last = writes > before the crash. I believe that both are bad. > Use softupdates on your filesystems and use a good UPS and hardware to > minimize the risk of a crash. >=20 > You have a good UPS on your production systems, dont you =3D0) Yes, I do. I realize that for most installs this isn't a significant = issue. I just wish http://www.freebsd.org/features.html would better = explain that softupdates doesn't sacrifice filesystem integrity, instead = of broadly saying softupdates doesn't sacrifice "reliability" which in = some ways it apparently does. ------=_NextPart_000_00C9_01C1E3C8.7A9F5030 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
> > FreeBSD Claim:
> > = http://www.freebsd.org/features.html
> > Soft Updates allows improved file system performance = without=20 sacrificing
> > safety and reliability
> >
> = > A Unix=20 Expert's Claim:
> > http://cr.yp.to/qmail/faq/reliability.html
> > ``Do not use async or softupdates filesystems. If you = do, and=20 if your system
> > crashes at the wrong moment, you will lose=20 [data].''
>
> Sofupdates ensure that the = *filesystem* is not=20 corrupt after a crash.
> They don't say anything about *data*. You = may=20 lose data after a crash.
> If you are worried about losing data, = you can=20 mount the filesystems
> sync, but I don't think you'll like the=20 performance. =3D0)
I suspect the world widely acknowledges = FreeBSD as=20 a strong server platform, at least more so than as a=20 strong workstation platform (I use it for one of my workstations, = but at=20 work everybody uses Windows).  If you accept that premise, then = does it=20 follow that the default install of FreeBSD should be geared toward a = server=20 instead of a workstation?  As a server, what are its most common = deployment=20 scenarios?  Web servers & mail servers?  Under a = standard web or mail server setup, is the disk I/O the most likely=20 bottleneck?  If so, then I suspect leaving softupdates turned on by = default=20 is reasonable.  If the bottleneck is something else (bandwidth, or = perhaps=20 even no bottleneck at all under most setups), then does it not make = sense to=20 offer the most reliability that's possible, at least by = default?
 
Looking at DJB's claim again up top, I = suspect that=20 he desires his software to really "mean it" when it responds to=20 a client saying it successfully received mail.  And = the best=20 definition of "mean it" in this context is that the mail is safely = written to=20 disk (I'd personally go a step further and have it safely written to a = cluster=20 of servers' disks, but that's certainly not reasonable for most=20 environments).  If softupdates indeed compromises that=20 feature, though, then couldn't a faint shadow of doubt be = cast=20 over the reliability of the entire default install?
 
> IMHO, filesystem corruption is far = worse than=20 data loss of the last writes
> before the crash.
I believe that both are = bad.
 
> Use softupdates on your = filesystems and use a=20 good UPS and hardware to
> minimize the risk of a crash.
> =
>=20 You have a good UPS on your production systems, dont you = =3D0)
Yes, I do.  I realize that for = most installs=20 this isn't a significant issue.  I just wish http://www.freebsd.org/features.html would = better explain=20 that softupdates doesn't sacrifice filesystem integrity, instead of = broadly=20 saying softupdates doesn't sacrifice "reliability" which in some = ways it=20 apparently does.
 
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