Re: [exim] FreeBSD ffs vs. ufs?

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Author: Tony Finch
Date:  
To: Marcus Barczak
CC: exim-users
Subject: Re: [exim] FreeBSD ffs vs. ufs?
On Mon, 17 Jul 2006, Marcus Barczak wrote:
>
> I'm currently doing some performance tuning on a pretty heavily used
> exim server we have here. We're running FreeBSD 6.1 and am noticing
> the disk loading to be quite high. The filesystems are currently
> configured as UFS however i'm contemplating using tunefs to switch
> them to FFS with soft updates enabled.


UFS and FFS are the same, though in BSD "UFS" refers to a layer between
the VFS and the on-disk structure, which could be FFS or (in the past)
LFS.

> I was wondering if anyone had any positive or negative experience
> with using ffs+soft updates with exim on a FreeBSD system? I
> understand the risk of losing data in the event of a power failure
> (soft updates not being written to disk immediately).


Note that Exim calls fsync whenever anything important happens to a
message, and softupdates guarantees that fsync works properly, i.e. that
the file and all its metadata will be committed to disk. Therefore if you
have a crash, you'll only lose messages which you had not yet completely
received - i.e. the senders will still have them.

Tony.
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