[Dovecot] OT - small hd recommendation

[Spyros Tsiolis]

Ditto,

Don't know anything on RAID 10 with four disks, but I agree with the two-disk scenario.

s.


 
----
"I merely function as a channel that filters 
music through the chaos of noise"
- Vangelis


________________________________
From: Thomas Harold <thomas-lists at nybeta.com>
To: dovecot at dovecot.org
Sent: Friday, 2 September 2011, 3:23
Subject: Re: [Dovecot] OT - small hd recommendation

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.)