Performance - Network RAID Impact?

[Paul Hutchings]

I'm looking into the P4000 and I'm struggling to find any indication of expected performance for the different models taking into account network RAID.

I know that being able to choose the RAID level per LUN means there is no simple answer, but with something like, say Exchange, would using a higher level of network RAID result in better or worse performance because on the one hand I assume you're involving more spindles when reading data, but you're also involving more spindles for any write operation?

I suspect the MDL Starter SAN or one of the SAS models is where we'd be aiming depending what HP come back with on pricing, and I suspect we'd be looking at four nodes with dedicated iSCSI switches.

[Bryan McMullan]

It completely depends on your workload. If your workload is read intensive, NW RAID5 or 6 will work well.

If your workload is write intensive, you will have a penalty for going to NW Raid 5 or 6.

For Exchange, it is heavily dependent on the version. Exchange 2003 and earlier is very disk/write intensive, whereas 2007-2010 not so much.

[Mike Povall]

Hi Paul,

If you are after performance there are a couple of points to note. The P4300 models use 8 disks in a single array within the module where the P4500 uses two groups of six disks and the module level. Then the SAS models use 15000rpm SAS drives where the MDL models are using 7200rpm disks - effectively SATA performance characteristics.

When using NW RAID5, NW RAID 6 would be unavailable to you at present on four nodes, the underlying data may be stored as NW RAID5 but the volume will be 'fronted' by a NW RAID10 snapshot to ensure performance. The data from the NW RAID10 area is combined into the underlying data through a scheduled task.

Regards, Mike.

[Paul Hutchings]

Sorry to drag this back up but I was just looking and noticed the comment about the P4500 using 2 groups of 6 disks per node - what does this mean in real-world terms please?

[Jim Silvia]

It's my understanding that there are two separate RAID5 sets and that the data is striped across both RAID 5 sets. The following image illustrates (they only have 4 drives though).

RAID50 only seems to be implemented on the P4500's (12 drives). Those bundles that only come packaged with 8 drives have a single RAID5 set.

One drive in each raid set can fail without a loss of data.

http://en.wikipedia.org/wiki/File:RAID_50_4_drive_example.png

[Paul Hutchings]

Hmm that's interesting.

I'm trying to do some sums on nodes and RAID volumes and the capacity just keeps on falling :-)

[Mark...]

Hi,
It sure will!
As an example using HP's P4000 planning guide...
Start with 60TB raw storage
select HARDWARE raid10
and then Network RAID 10 or old NR2 for all disks
and you get... 6.6TB !!! usable space !!!
Mark...

[Paul Hutchings]

OK so let's say I have 3 x AX701A which is 21.6 RAW, 16.05 usable according to the teledata calculator in RAID50 config.

Presumably the recommendation is still to use network RAID5 as a bare minimum?

I'm looking to spec a system that would potentially store 8tb or so (and growing slowly) of file data, and 2tb or so of VM's.

I'm still struggling a little to wrap my head around the mix of hardware RAID, and the NW RAID (I should have a reseller coming in but it would sure help if HP had their own online calculator).

[Mark...]

Hi
opps - sorry!
My example above should have said Network Raid 10+2 or old NR4 (not just 10!)
Mark...