On 09/09/2011 22:52, Emmanuel Halbwachs wrote:
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.
I still would go with option A -- you actually gain a lot of it. All the logs and OS specific operations + MTA spools will go on a separate set of spindles and in some situations that helps a lot.
Make sure you get battery for the PERC controller with ideally 1GB NV cache -- it makes difference especially for massive amount of small writes which I'm sure you are going to have.
Also, I am not sure how dovecot handles fsync() however this can be pain in the ass if you are using ext3/4 file system which by the way is definitelly not the right choice in this case ;-) (what you already know I am sure).
I went through similar problem few months back - we were considering upgrading our mail server for 200+ mail accounts (~ 400 mail addresses in total) and we ended up... getting Google Apps for Businesses. Highly recommend just having a look at it -- cost wise it looks a bit scary initially but you are gaining *a lot*.