Re: RAID config for mailboxes host

In my opinion and experience with email systems off 100k+ users I would put all 12 disks in a raid 10 array.    This is as long as you're using a decent MTA which doesn't beat up your disks before actually writing the message to the user's dir including any local virus/spam scanning.  

Since you are planning on Dovecot I would also research using their new alternative to Maildir called dbox.  I have only tested it in non production environments on top of GlusterFS.

So to sum it up:    Postfix + Dspam + dovecot.   Add in the dovecot dspam plugin so your users can train dspam just by moving messages into their spam folder via their imap client.

Cory
Sent from my U.S. Cellular BlackBerry® smartphone

-----Original Message-----
From: Emmanuel Halbwachs <[email protected]>
Date: Fri, 9 Sep 2011 23:52:13 
To: <[email protected]>
Subject: RAID config for mailboxes host

Hello,

Slightly OT because not Debian specific.

Let this physical server:

    Dell R710
    2x6 cores 2.3 GHz
    48 GB RAM
    12 disks 600 GB, 15 ktr/min
    only one RAID card H700

for the usage of a rather small mailhost:

    MDA
    IMAP/POP for 1500 mailboxes (Maildir)
    webmail
    (MX are other machines)

We consider two RAID config for the 12 disks:

        A   2 disks RAID 1 for system
           10 disks RAID 6 for mailbox space

        B  12 disks RAID 6 for the whole 

In A, we lose 1.2 (raw) TB with respect to B. Advocates of A say that
in B, the heads read/write activity of the mailboxes will seriously
impact the system performance. In A, the system has its own axes,
separate from the mailboxes ones.

Side note: We are considering dovecot.

Do you think that the performance loss will be so visible that it
worth sacrifying 1.2 TB of mailbox space?

Facts are far better than guesses, but how to bench those two configs,
with which test protocol, and how realistic?

Thanks,

-- 
Emmanuel Halbwachs                       Observatoire de Paris-Meudon
Resp. Réseau/Sécurité                           5 Place Jules Janssen
tel  :  +33 1 45 07 75 54                        F 92195 MEUDON CEDEX
fax  :  +33 1 45 07 01 89      véhicules : 11 av. Marcellin Berthelot


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