Question : Problem: Entry Level SAN OK for "Mission Critical" ?

Hello,

We're in the process of implementing a brand new Exchange 2007 mail system AND upgrading our file servers.  We are considering an ISCSI only SAN (HP 1510i) or a SAN which has both fiber & ISCI connectors (HP Storage Works 4000).  

The entry level SAN is classified by HP as an "entry level" whereas the bigger one is touted for "mission critical applications".

Well, to our 500 users, their 5TB of stuff is mission critical.

Question:
How much more "reliable" would the bigger SAN be if they are both using the same HD's (10,000 SCSI drives)?  

The entry level SAN sports RAID6 to withstand TWO drive failures.  At first glance, it's not clear if every component is redundant (e.g. power supplies, controllers, etc.)

I guess I'm asking: if by chance both SANs have the same redundancies, what would make the bigger one more appropriate for "Mission Critical" applications?

Any and advice much appreciated.

Thanks,
Mike

Answer : Problem: Entry Level SAN OK for "Mission Critical" ?

The primary differences in devices like you mentioned are in the capabilities of the controller.   It doesn't matter that perhaps the drives are the same between the boxes; what matters is the capability of the controller, what redundant features are built in ,etc.

For a "mission" critical environment, you will want something that supports:

a) Multiple drive failures
b) Hot swap drive replacement
c) on-the-fly raid device resizing
d) The abilitiy to create clones and snapshots
e) battery-backup for cache items (i.e., writeback cache battery)
f) multiple power supplies
g) multiple controllers

Offhand, the HP storageworks line of storage is pretty good stuff.   There are multiple levels of storage arrays they offer that have some or all of the features above.

Don't be cheap.   I have seen too many system environments spend all their money on servers, and then the leftovers of the budget on some cheap NAS solution.   bad bad bad.