I am looking to build a very high density storage pool: a rack containing a c7000 chassis with 6 MDS600 arrays with the newly announced Seagate 3TB SAS drives will give me 1260TB with sufficient CPU horsepower. I am trying to decide how to configure the RAID pools. My initial thought is to create many 14-drive RAID6 pools (assigning each blade multiple pools).

Can I configure the system so that RAID pools span multiple MDS600 arrays? What is the maximum I/O that I can expect between the c7000 and the drive arrays and what options do I need to acquire to achieve that performance?


Because of the high density, I had to use SAS/SATA over FC drives (we've been successful in acquiring drive caddies and racking our own drives in HP gear to save quite a bit of money). It appears that the MDS600 is the highest density array that HP sells. (I am not tied to HP, but they seem to make good kit.) I'm still reading up on the configuration of the SAS switches. I'll be using the BL460c with dual 5675.

The OS will be CentOS (5 or 6) with our application running on the blades. My initial assumption is to give each blade a few pools (still kicking around whether to use larger RAID-6 pools, smaller RAID-5 pools, and how many spares) to handle RAID rebuild times.


You won't be able to use those Seagates sorry, just won't work without HP custom firmware, I also doubt any disk over 2.1TB will work in a current generation MDS600. Also you don't mention how many blades of what type you want to use, there's a limit of 100 disks per P700m mezz card but that many disks per controller wouldn't perform terribly well.

As for RAIDing across drive shelves, well yes you can do that but ther are rules to be observed, come back with more details of your planned layout plus OS too.

  • Hmm. We use normal Seagate drives elsewhere (it works with DL180G6, DL360G7, DL380G7, and D2600). I'm surprised that it wouldn't work in an MDS600. (Good point on the capacity though.) I edited the query to indicate the blade. I'm presuming a max of about 50-75 drives per blade. I suppose that I can always populate both mezzanines with p700s.
    – sfried
    Apr 14 '11 at 22:52
  • Obviously you have more experience using non-HP disks than me, you'd have to try it first I guess. Regarding performance if you have 50-70 disks per controller you'll very often 'max-out' the SAS links but I doubt you'd be able to saturate each servers 10Gbps link/s - but you should manage perhaps 5-6Gbps overall with two mezz's. No idea about how to carve up the disks sorry, I'm a RAID 10 snob :)
    – Chopper3
    Apr 15 '11 at 5:47
  • I'm surprised that two p700s could only manage 5-6 Gbps. We are getting 1GB reads, 600MBps writes from a single p812. Any idea if the dual lane the MDS600 has for SAS drives vs single for SATA will improve performance?
    – sfried
    Apr 15 '11 at 10:53
  • Well the absolute max theoretical unidirectional speed off a P700m onto the bus is only 2GBps and the max up the SAS links is only 3.2GBps, that's theoretical too and only if you balanced the disks right anyway. Plus of course that's with sequential access and no RAID overhead/latency.
    – Chopper3
    Apr 15 '11 at 11:17
  • From the HP rep: A blade can only support one controller. But, a P712 6g controller (and use 6g SAS switches and a configuration that crosses MDS600s), will maximize drive performance. Also, the rep expected that the MDS600 will support the 3TB drives once they're qualified.
    – sfried
    Apr 15 '11 at 18:49

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