Date: Mon, 19 Aug 2002 22:54:32 -0400 From: "Brian T. Schellenberger" <bts@babbleon.org> To: Matthew Dillon <dillon@apollo.backplane.com>, freebsd-stable@freebsd.org Subject: Re: root (/) not soft-updates by default ? Message-ID: <200208192254.32172.bts@babbleon.org> In-Reply-To: <200208191604.g7JG4DOU077232@apollo.backplane.com> References: <20020819144928.GA6628@nebula.wanadoo.fr> <m3ofbylv71.fsf@merlin.emma.line.org> <200208191604.g7JG4DOU077232@apollo.backplane.com>
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I find that that the performance of my IDE drives is perfectly acceptable with write-caching turned off *if* I also enable softupdates on everything. This is for desktop use, not a server, but then again if I were running a server I believe that I'd use SCSI anyway. On Monday 19 August 2002 12:04 pm, Matthew Dillon wrote: | This conversation is moot, since modern IDE drives (and apparently | seeping into SCSI drives as well) do track-at-once writes to the physical | media, there is no ordering guarentee no matter what you do, and IDE | performance with write caching turned off sucks so badly you pretty much | *have* to turn it on if tags are not supported or suffer penalties so | severe that the last time we tried it our user community was up in arms | over the result. | | So short of caching the data in NVRAM you are *screwed* no matter what | you do. Oh, wait, even caching the data in NVRAM doesn't save us, | since track-at-once writes rewrite sectors we never modified. So we might | as well turn write caching on. If you don't like the default, you can turn | it off in /boot/loader.conf. | | In any case, Jaime Bozza's explanation (the smallish root can fill up | with softupdates enabled when installing a new system over the old one) is | the correct one. This issue is fixed in -current's softupdates but not | fixed in -stable's. The business about IDE not ordering writes is also | correct, but the statement that softupdates is somehow *worse* then a | normal mount with an IDE disk is not correct. Both are equally dangerous | due to the track-at-once writes which IDE drives tend to do these days. | | Since very little on the root partition is modified once a system has | come up, not enabling softupdates on root is not a big deal. | | -Matt | Matthew Dillon | <dillon@backplane.com> | | To Unsubscribe: send mail to majordomo@FreeBSD.org | with "unsubscribe freebsd-stable" in the body of the message -- Brian, the man from Babble-On . . . . bts@babbleon.org (personal) To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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