Subject: Re: softdep?
To: Luke Mewburn <lukem@goanna.cs.rmit.edu.au>
From: Roger Brooks <R.S.Brooks@liverpool.ac.uk>
List: current-users
Date: 03/26/1999 18:40:25
On Sat, 27 Mar 1999, Luke Mewburn wrote:
>Chris Jones writes:
>> As I understand it (which understanding may be orthogonal to reality),
>> the prestoserve card was originally used to cache NFS writes. One of
>> the ideas thrown around in the discussion I mentioned, though, was
>> caching all metadata, in addition to NFS writes, on the card. The
>> could theoretically give you some really spiffy filesystem
>> performance.
>
>As far as I understand it, presto doesn't just `cache NFS writes'. It
>actually caches all synchronous writes to the local disk (which writes
>from the NFS server daemon are, to comply with the NFSv2 spec).
>Metadata writes happen to be synchronous too, so they get a speedup as
>well.
Indeed. I remember poking about on a SunOS 4.1.3 system after running
the wonderfully-named presto_chango script which modified the kernel
build files to use the prestoserve. It hooked the disk driver I/O
routines in the device switch. Sun used to claim that it speeded up
local disk access as well (and by default it would accelerate all
filesystems, including / /usr and /var), although we never bothered
trying to measure the performance enhancement.
Roger
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