Date: Sun, 14 Apr 2002 15:24:33 -0400 From: "Gregory Keefe" <keefeg@keefeg.com> To: "Fernando Gleiser" <fgleiser@cactus.fi.uba.ar> Cc: <freebsd-questions@freebsd.org> Subject: Re: Softupdates Message-ID: <00cc01c1e3ea$03382c70$9865fea9@GPC> References: <20020414122514.E5464-100000@cactus.fi.uba.ar>
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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 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=3DContent-Type content=3D"text/html; = charset=3Diso-8859-1"> <META content=3D"MSHTML 6.00.2715.400" name=3DGENERATOR> <STYLE></STYLE> </HEAD> <BODY> <DIV><FONT face=3DArial size=3D2></FONT> </DIV> <DIV><FONT face=3DArial size=3D2>> > FreeBSD Claim:<BR>> > = </FONT><A=20 href=3D"http://www.freebsd.org/features.html"><FONT face=3DArial=20 size=3D2>http://www.freebsd.org/features.html</FONT></A><BR><FONT = face=3DArial=20 size=3D2>> > Soft Updates allows improved file system performance = without=20 sacrificing<BR>> > safety and reliability<BR>> ><BR>> = > A Unix=20 Expert's Claim:<BR>> > </FONT><A=20 href=3D"http://cr.yp.to/qmail/faq/reliability.html"><FONT face=3DArial=20 size=3D2>http://cr.yp.to/qmail/faq/reliability.html</FONT></A><BR><FONT = face=3DArial=20 size=3D2>> > ``Do not use async or softupdates filesystems. If you = do, and=20 if your system<BR>> > crashes at the wrong moment, you will lose=20 [data].''<BR>></FONT></DIV> <DIV><FONT face=3DArial size=3D2>> Sofupdates ensure that the = *filesystem* is not=20 corrupt after a crash.<BR>> They don't say anything about *data*. You = may=20 lose data after a crash.<BR>> If you are worried about losing data, = you can=20 mount the filesystems<BR>> sync, but I don't think you'll like the=20 performance. =3D0)<BR></FONT></DIV> <DIV><FONT face=3DArial size=3D2>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?</FONT></DIV> <DIV><FONT face=3DArial size=3D2></FONT> </DIV> <DIV><FONT face=3DArial size=3D2>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?</FONT></DIV> <DIV><FONT face=3DArial size=3D2></FONT> </DIV> <DIV><FONT face=3DArial size=3D2>> IMHO, filesystem corruption is far = worse than=20 data loss of the last writes<BR>> before the crash.<BR></FONT></DIV> <DIV><FONT face=3DArial size=3D2>I believe that both are = bad.</FONT></DIV> <DIV><FONT face=3DArial size=3D2></FONT> </DIV> <DIV><FONT face=3DArial size=3D2>> Use softupdates on your = filesystems and use a=20 good UPS and hardware to<BR>> minimize the risk of a crash.<BR>> = <BR>>=20 You have a good UPS on your production systems, dont you = =3D0)<BR></FONT></DIV> <DIV><FONT face=3DArial size=3D2>Yes, I do. I realize that for = most installs=20 this isn't a significant issue. I just wish <A=20 href=3D"http://www.freebsd.org/features.html"><FONT face=3DArial=20 size=3D2>http://www.freebsd.org/features.html</FONT></A> 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.</FONT></DIV> <DIV><FONT face=3DArial size=3D2></FONT><FONT face=3DArial=20 size=3D2></FONT> </DIV></BODY></HTML> ------=_NextPart_000_00C9_01C1E3C8.7A9F5030-- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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