[techtalk] Raid and IMAP

moebius at ip-solutions.net moebius at ip-solutions.net
Wed Mar 22 13:20:33 EST 2000

Hey Robert,
  Below are the specs 

> What do you want to speed up? Or better, what is to slow for your
> needs? Where do you think is more perfermance possible?

Well, it seems that in mail/IMAP generally the bottleneck is always disk
I/O. I am hoping to gain performance from a SCSI software raid array. I'm
thinking raid 0+1. 

> Now the important questions: How many Users? Where are the
> Homedirectories (no nfs)? What MailTransferAgent do you use? Do you
> have quotas? Is the mailserver relay or _the_ mailhost or is it just
> receiving the mail for the x users? How many mails go in which
> direction (approximately)?

Looking at approx. 200 users, home directories are currently on a
partition of the second ide drive (/home/*). I am not using NFS and hope
not to have to use it. The mailserver relays for the webserver so that
those checking mail via TWIG will have any info in the same place,
ie->mailserver. The mail server also runs SPOP, IMAP, and ssh for pine
connections. This MTA is sendmail and IMAP is UW (although I'm looking at
Cyrus). As for the mail, it's the old 80/20 rule. I've got a few users who
get approx 500-700 mails a day with the rest probably averaging 40 per

> Further questions: How do you backup the homedirs? Size of the
> homedirs? Mailspoolsize now? How many disks of which size do you have
> for your RAID?

Backup is currently done with a Travan tape drive daily incremental with
weekly full backup. Don't know what the current spool size is. I do have
quotas of 10M in effect for all but a few users. I am thinking about 2
Adaptec 2940UW card holding 3 9.1G drives each. The reason for this is to
seperate the user directoies into two sections (ie a and b) and try to do
load balancing that way.

I definetley do want to play with Raid but also need to make sure that it
does the job. If I were doiing it with IDE drives than i wouldn't sweat it
but the SCSI are a little more colstly and I would like to be able to
justifiy my expense.
> If you just want to play with RAID take the homedirs.  (:
> Ciao,
> 	Rob
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