[horde] Bottleneck ? CPU or HDisk IO or RAM

[Rob MacGregor]

On Tue, Feb 3, 2009 at 09:04, Linux Advocate <linuxhousedn at yahoo.com> wrote:
> good questions rob, thanx for making things clear... my answers below...

>> 1) How many *concurrent* users?
>
> say 1000? or about 70% at any one time.

Is that a guess, or a figure arrived at in a meaningful manner?  If
the reality is half that then you'll potentially spend far more than
you need.

Are the emails largely static, or do you have a large volume of
incoming and/or outgoing?  If it's largely static then caching will
help massively, if it's largely dynamic then it won't help as much.

>> 2) What IMAP server?
>
> dovecot

Maildir or mbox?  Have you followed any of their published tuning
advice (http://wiki.dovecot.org/PerformanceTuning)?  Have you
consulted the dovecot mailing lists (particularly their archives) for
advice on configuration and sizing?

>> 3) What configuration of SATA drives?  A single 1 TB drive will be
>> slower to read than a pair of 1 TB in a RAID0, which will be slower
>> than 4 half TB drives in a RAID10.  Good quality (ie expensive) SATA
>> RAID will be faster than cheap hardware RAID, and software RAID may be
>> faster than cheap hardware RAID.
>
> say 6 x 750 GB Sata disks

Configured how - is that a 6 disk RAID5 array or a 6 disk RAID10 array
(ie a stripe of 3 RAID1 pairs)?  Is it hanging off a hardware RAID
controller (brand and model?) or as a software RAID?  What type of bus
is it hanging off of if it's a controller (PCI, PCI-X, PCIe etc)?

-- 
                 Please keep list traffic on the list.

Rob MacGregor
      Whoever fights monsters should see to it that in the process he
        doesn't become a monster.                  Friedrich Nietzsche