Date: Mon, 10 Jul 2000 13:04:05 GMT From: Salvo Bartolotta <bartequi@inwind.it> To: Doug Barton <DougB@gorean.org> Cc: freebsd-questions@FreeBSD.ORG, djkanter@northwestern.edu Subject: Re: Softupdates question Message-ID: <20000710.13040500@bartequi.ottodomain.org> References: <20000709005612.A89313@localhost.localdomain> <20000709.23515500@bartequi.ottodomain.org> <3969172D.D3A30104@gorean.org>
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>>>>>>>>>>>>>>>>>> Original Message <<<<<<<<<<<<<<<<<<
On 7/10/00, 1:22:05 AM, Doug Barton <DougB@gorean.org> wrote regarding
Re: Softupdates question:
> Salvo Bartolotta wrote:
> > If performance is your main concern, you may wish to enable
> > softupdates and the "noatime" option for all filesystems except for
> > "/". This last filesystem ("/") should (normally) be used only with
> > the "noatime" option.
> I've read many posts from some really smart people that said not=
only does
> noatime not help you in combination with softupdates, but it can
actually
> hurt you. Also, you shouldn't be doing a lot of i/o on your root
filesystem
> anyway, so I wouldn't advise using noatime on that one either.
> Good luck,
> Doug
Dear Doug Barton,
thank you very much for writing.
My understanding was that the noatime option reduced writes, as per
TFM (mount(8)):
<blockquote>
noatime
Do not update the file access time when reading from a
file. This option is useful on filesystems where there
are large numbers of files and performance is more criti-
cal than updating the file access time (which is rarely
ever important). This option is currently only supported
on local filesystems.
</blockquote>
Essentially, I thought that avoiding these writes in conjunction with
softupdates (smart metadata management) would not do harm.
Also, a number of posts had showed that a few people were actually
using softupdates *and* noatime.
However, I searched -questions, -fs, -hackers, -stable, and -arch (!),
once again for the string "softupdate* and noatime".
Alas, I have not found any clues: rather, it seems that most
authoritative posts (even explicitly) suggest using softupdates
**and** noatime in order to improve performance.
Ok, I am a little confused now :-)
Would you be so kind as to shed more light on the whole matter
(also providing appropriate pointers/material/evidence) ?
I have been using softupdates (+ noatime) for a few months,
so I am particularly intested in correctly understanding the potential
issues and/or dangers connected with this filesystem policy and
noatime.
Many thanks in advance and best regards,
Salvo
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