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From: hohmuth@irs.inf.tu-dresden.de (Michael Hohmuth)
Newsgroups: comp.unix.bsd.freebsd.misc
Subject: Re: Prestoserve for FreeBSD?
Date: 21 Dec 1995 00:33:28 +0100
Organization: Dept. of Computer Science, TU Dresden, Germany
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Message-ID: <4ba6g8$aph@irzr17.inf.tu-dresden.de>
References: <nbg0Z9M@quack.kfu.com>
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In article <nbg0Z9M@quack.kfu.com>, Nick Sayer <nsayer@quack.kfu.com> wrote:
> For those of you unfamiliar with the concept, PrestoServe is an
> idea Legato came up with and Sun ended up selling for sparc servers.
> In short, it is a board with 1M of NVRAM (battery backed static).
> The RAM is used by a little driver that sits at the bottom of the
> UFS drivers and above the disk drivers to cache synchronous writes.
> When used on a news machine, I have witnessed the unpack rate
> double, and the efficiency of fastrm go straight through the roof.
> Since it only caches synchronous writes, the small ammount of
> RAM can be put to maximum use, and since it's battery backed, it's
> no less safe than if it were written straight to disk (a 'dirty reboot'
> results in the dirty buffers being flushed on the first disk access).
I agree that Presto is nice for NFS servers (which are required to
write their data synchronously), but for a news partition, wouldn't
turning off synchronous writes of file system meta data ("mount -o
async") have the same effect? Given that a news server stays up for
months, and doesn't contain any essential data, and believing the
Linux guys which tell us that async writes almost never render a file
system unrepairable after a crash...
Michael
--
Email: hohmuth@inf.tu-dresden.de
WWW: http://www.inf.tu-dresden.de/~mh1/