How much does disk speed matter?

[Livin]

I'm getting my first NAS (without drives) on Tues and curious as to real-world results with using 7200 vs 5400/5900 rpm drives when talking about a decent quality NAS.

I'm specifically getting a Thecus N2200XXX which only holds 2 drives so I will mirror them but I'm also interested in how drive speed affects larger 4 & 5 drive NASes.

Lets talk about a few specific cases (assume gig network in all cases)...

2 disk RAID 1
4 disk RAID 10
4 disk RAID 5
5 disk RAID 5

 

[GregN]

I'm getting my first NAS (without drives) on Tues and curious as to real-world results with using 7200 vs 5400/5900 rpm drives when talking about a decent quality NAS.

I'm specifically getting a Thecus N2200XXX which only holds 2 drives so I will mirror them but I'm also interested in how drive speed affects larger 4 & 5 drive NASes.

Lets talk about a few specific cases (assume gig network in all cases)...

2 disk RAID 1
4 disk RAID 10
4 disk RAID 5
5 disk RAID 5

In the case of RAID there are three factors more important than drive speed:

Number of Spindles, the larger the number of disks the better the performance. You get better performance with a large number of small disks than vice versa.

Stripe Size, a little more nuanced involving usage patterns, but tuning your stripe size to how you use your RAID array, and to the filesystem boundaries can really pay off.

Cache size, both on the disk, on the controller card and in the machine/nas.

In the case of Ol'Shuck, where the network was not a factor (4Gb Fiber), drive speed made very little difference - whereas the number of disks in the RAID unit, and stripe size helped significantly. But best of all, setting Write-Back policy had a huge impact.