[Dovecot] OT - small hd recommendation

[Thomas Harold]

On 9/1/2011 12:48 PM, Daniel L. Miller wrote:
>
> Given my extensive requirements - I haven't yet filled my existing 320GB
> - size isn't a big deal. Am I actually deriving much benefit from 4-disk
> RAID10 using 160GB discs - vs a 2-4 disc 1TB RAID1 array?
>

A pair of RAID-1 mirrors:

- easy to deal with
- you can attempt to manually balance load between the two arrays 
(storage on one pair, indexes and mail queue on other pair)
- disks can be pulled and taken to another machine and read one by one
- slightly harder to screw up (but both setups die if the wrong 2 disks 
fail)

RAID-10 over 4 disks:

- generally faster seeks
- generally faster read/write speeds due to striping
- generally the better choice for performance
- a bit harder to bury the disks vs a pair of mirrors
- lets you have a bigger partition
- all the eggs in a single array

If you're having performance problems on the existing RAID-10, your only 
real choices are to throw more spindles at it (move to a 6 or 8 disk 
RAID-10 w/ a hot-spare disk), throw faster spindles at it (10k/15k SAS), 
or move to SSD.

So, if you think you can manually balance the needs of the system, you 
could try a pair of independent mirrors.  But if you want less hassle, 
stick with the RAID-10.

(And look into a tool like "atop" which can be run in the terminal and 
does a decent job of showing you whether the CPU/DISK is overly busy.)