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Subject: Re: Redhat Linux, Mailman and Sendmail
From: Andrew McNamara (andrewmconnect.com.au)
Date: Wed Apr 05 2000 - 19:39:17 CDT

> As I thought. Wietse demonstrated in his earlier tests that
>using async mounts under Linux is as much as seven times faster than
>synchronous mounts with asynchronous syslog writes, but we all know
>that using async mounts is not safe, and is a violation of RFC 1123.
>
> Contrariwise, using softupdates on FreeBSD *is* safe, and should
>result in at least the same level of performance, if not better.

When you say "safe", are you referring to the requirement in RFC 1123
that says the destination must not positively acknowledge a transaction
until it is committed to stable storage?

While soft updates are very cool, and do guarantee that at any instant
in time, your filesystem structure is consistent, their performance win
comes from dropping the restriction that metadata updates be
synchronous. This means control is returned to the user process before
their file is committed to disk - in the case of an MTA, it would send
back an ACK to the remote end before the metadata was committed unless
it used fsync().

 ---
Andrew McNamara (System Architect)

connect.com.au Pty Ltd
Lvl 3, 213 Miller St, North Sydney, NSW 2060, Australia
Phone: +61 2 9409 2117, Fax: +61 2 9409 2111