Subject: disk usage and speed

From: Dennis Nilsson <[email-masked]>
Date: Tue, 09 Mar 2004 13:08:35 +0100

Hi all

I have a setup where i have around 200 user and they sometimes have 
mailboxes of 2GB i size
in our current setup we are running an old imap version from the RH 6.2 
release on a 800Mhz machine with 800 MB memory. it also have
an SCSI 2 disk raid ( not very fast).
We have problems when our mail space runs low and a user wants to delete 
some mail, if the user have a mailbox around 1-2 GB in size he cant
delete the mail. we also have speed problems, users somtimes wait 
minutes for a server response..

our new setup is a 3 Ghz machines with 2 GB memory and a RAID 5 storage 
of 400 GB. it runs Redhat Enterprise ES.

the question is:
          Will speed of the new system be good enough, even if a user 
with the 2GB mailboxes starte to delete spam mails.

          Will the IO load of the system be large.

           how does Imap 2002d delete a message from a mailbox, will it 
do a copy of the entire mailbox or can it delete a message in one large file
           without to much IO.

           or do i have to choose a IMAP server that stores mails i 
single files in Unix folders.

thanks
Dennis

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From: Mark Crispin <[email-masked]>
Date: Tue, 9 Mar 2004 07:06:48 -0800 (PST)

> with the 2GB mailboxes starte to delete spam mails.

CPU speed is rarely the issue.  IMAP servers tend to be I/O bound.

>         Will the IO load of the system be large.

Yes.  The more spindles you have (as opposed to single gigantic disks), 
the better.  Definitely separate the mail spool on a different disk from 
user mailboxes.

> do a copy of the entire mailbox or can it delete a message in one large 
> file without to much IO.

It depends upon the mailbox format.  In traditional UNIX format, it has to 
rewrite the mailbox from the point that the deleted message is located to 
the end of the mailbox.

-- Mark --

http://staff.washington.edu/mrc
Science does not emerge from voting, party politics, or public debate.
Si vis pacem, para bellum.