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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[-- Attachment #1 --] > > 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. =0) 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. > > You have a good UPS on your production systems, dont you =0) 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. [-- Attachment #2 --] <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; charset=iso-8859-1"> <META content="MSHTML 6.00.2715.400" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>> > FreeBSD Claim:<BR>> > </FONT><A href="http://www.freebsd.org/features.html"><FONT face=Arial size=2>http://www.freebsd.org/features.html</FONT></A><BR><FONT face=Arial size=2>> > Soft Updates allows improved file system performance without sacrificing<BR>> > safety and reliability<BR>> ><BR>> > A Unix Expert's Claim:<BR>> > </FONT><A href="http://cr.yp.to/qmail/faq/reliability.html"><FONT face=Arial size=2>http://cr.yp.to/qmail/faq/reliability.html</FONT></A><BR><FONT face=Arial size=2>> > ``Do not use async or softupdates filesystems. If you do, and if your system<BR>> > crashes at the wrong moment, you will lose [data].''<BR>></FONT></DIV> <DIV><FONT face=Arial size=2>> Sofupdates ensure that the *filesystem* is not corrupt after a crash.<BR>> They don't say anything about *data*. You may lose data after a crash.<BR>> If you are worried about losing data, you can mount the filesystems<BR>> sync, but I don't think you'll like the performance. =0)<BR></FONT></DIV> <DIV><FONT face=Arial size=2>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?</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>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?</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>> IMHO, filesystem corruption is far worse than data loss of the last writes<BR>> before the crash.<BR></FONT></DIV> <DIV><FONT face=Arial size=2>I believe that both are bad.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT> </DIV> <DIV><FONT face=Arial size=2>> Use softupdates on your filesystems and use a good UPS and hardware to<BR>> minimize the risk of a crash.<BR>> <BR>> You have a good UPS on your production systems, dont you =0)<BR></FONT></DIV> <DIV><FONT face=Arial size=2>Yes, I do. I realize that for most installs this isn't a significant issue. I just wish <A href="http://www.freebsd.org/features.html"><FONT face=Arial size=2>http://www.freebsd.org/features.html</FONT></A> 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.</FONT></DIV> <DIV><FONT face=Arial size=2></FONT><FONT face=Arial size=2></FONT> </DIV></BODY></HTML>help
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