HP MSA2312 SAN. Spare disks?

[Gongalong]

Hi folks,

 

Our SAN (HP MSA2312) has or rather had a spare HDD.

 

(As background the SAN is configured with two VDISKS. One holds Hyper-V OS VHDs (RAID5) and the other carries Data VHDs (RAID6).)

 

The SAN is supported by a thirdline consultant (it's all far too clever for me!), and we were told that the spare disk wasn't actually necessary when we switched to another consultant.

 

We ran out of space on the SAN so the spare HDD has been incorporated into the VDISK. The latest consultant said this isn't an issue as the Vdisks will not stop working if a drive fails because of RAID.

 

I just wanted to check if the above statement is correct?

 

TIA

[Netwacky87]

Thats my take on it yes, Raid 5 will stay functional if 1 drive is lost (any more than 1 and its goodbye) and raid 6 will stay working if you loose 2 drives but not 3...

 

Thats whats in my head, could be wrong but thats what ive always gone by!

[Gongalong]

As we're somewhat desperate for space I'd rather use the spare if we can, so if RAID can soak up at least one failed drive then I'm happy to take the risk.

[Domino]

The above is true, RAID 5 will tolerate a failed disk.

 

However, I have always run our SANs with a hot spare - the risk of disaster is too great not to IMHO

[Netwacky87]

When it comes to a SAN, fault tolerance comes before risk...IMO a disk wasted is better than having an entire array of nothing-ness

[Gongalong]

Oh well, it's being added into the array now, and basically we need it (due to a cock up by those who previously configured the VHDs). What could go wrong...