[Discuss] raid issues

[blu at nedharvey.com (Edward Ned Harvey (blu))]

> From: discuss-bounces+blu=nedharvey.com at blu.org [mailto:discuss-
> bounces+blu=nedharvey.com at blu.org] On Behalf Of Stephen Adler
> 
> Another question. As I try and configure this server which I'm getting
> for work, the key issue is its ability to have a lot of hot swappable
> disks. what I'm seeing these days is a migration to the 2.5" drives away
> from the 3.5". The problem is the 2.5" drives only go up to 1 terabyte,
> while the 3.5" drives go up to 6 terabytes. so what's up with this 2.5"
> drive bit. The literature says that they consume less power (the 2.5"
> drives) and are the favorite for data centers. But there's a factor of 3
> difference between the storage capacity and size. so the problem is that
> I have very few options when it comes to buying a rack mounted server
> with 3.5" hot swap-able drives. there seems to be a lot more rack
> servers with 2.5" drive bays.

The thing is...  All drives can do about 1 Gbit/sec.  Wanna go faster?  Use more drives.  (And choose raid configurations that optimize your performance.)  So even though 2.5" is limited to about 1T, and 3.5" can go much bigger, who needs it?  Just see how long it takes to read/write 6 TB of data with 1Gbit speed.  (Spoiler:  13 hours minimum.)

The speed of a drive is limited by your workload primarily (how much time spent doing random seeks) and secondarily, by the frequency response of the heads.  Wanna go faster, buy more heads.  One head per disk.


> Can anyone recommend a system with 16 3.5" drive bays?

I really like sans-digital.  When they sell you a chassis, it comes with all the caddies, so you can buy whatever disks you want.  But when you shop around, you discover, the best price on disks actually comes from them, when you buy the disks with the system.  Amazing!  And totally contrary to the industry standard.