VMware Cloud Community
F8Tech
Contributor
Contributor

RAID selection for HP P2000 SAS with ESXi 5

We received a HP P2000 LFF SAS today with 8 450GB 15k SAS drives, it will hold a max of 12. There will be 2 VM hosts (HP DL380 G7) conncted to it via SAS. There will be 4-6 VMs running initially with plans to use this for VDI at some point. We will be running Exchange and SQL on the VMs along with some other applications. We will be running VMWare Vsphere 5.


What RAID option should we go with with 8 drives? I was thinking RAID 5 with 6 or 7 drives and the remaining drives setup as hot spares.

Thanks!

8 Replies
kjb007
Immortal
Immortal

Typically, I recommend a RAID 5 configuration, to get the biggest bang for the buck in terms of space.  if you're using this in a production setting, however, your choices will vary baed on I/O profile of the apps that you will run on the system.  VDI is very different from DB, or exchange, and / or java based stuff.

If you're not going to support a large user base, then you should be ok with the RAID 5, but if you have a "large" number of users, this will impact the performance you're able to squeeze out of these spindles, along with the work that's being done on the server side.  I'd figure out how much IO I need for my servers, or the other way around with the desktops, and split my RAID groups.

-KjB

vExpert/VCP/VCAP vmwise.com / @vmwise -KjB
darkbgr123
Contributor
Contributor

I have the same hosts as you and had a similar dilemma. Only difference is I've loaded it with 12x 600GB 15000 rpm SAS LFF drives

Here is a test that HP published with the performance of the P2000 G3 SAS in various RAID modes:


http://h18004.www1.hp.com/products/quickspecs/13551_div/13551_div.HTML


RAID Type                           RAID10      RAID5          RAID6 Sequential Reads MB/s               1,650       1,650          1,650 Sequential Writes MB/s              850         1,350          1,100 Random Mix IOPs 60/40 Read/Write    23,500      16,000         9,800 Usable Capacity in my case          3,6TB       6,6TB      
   6TB

So 30% less performance average between RAID10 and RAID5, but 45% more usable space. Hmmm. I think I will go with a mix of RAID5 and RAID10. Of course the test was setup with 12 vdisks with 12 disks each (raw i/o), but still it's an indication.
I also heard it's best to create a big vDisk and then just split this vdisk in 500GB LUNs instead of provisioning several vdisks.
Do you have the dual controller version or single controller? Another consideration is that if you only have one vdisk the second controller won't be doing anything.
My intended use for the P2000 is for a vCloud integration manager proof of concept (1x management cluster with 17 VM's and 1x compute resources cluster with 30-35 VM's) So after considering these points in my case I think I will go with:
Vdisk1
4 drives in raid10, raw capacity 2400GB, usable 1200GB, presented to my management cluster as 2x 600GB LUNs (direct connected to server via sas 6gb). I have to run around 9 VM's out of each LUN.

Vdisk2
8 drives in raid5, for usable capacity around 4,2TB to be presented to the my compute cluster as 8x 600GB LUN's via sas direct-connect. I think I should be able to run 5 VM's off of each LUN.
PS. don't forget to install the ESXi plug-in for VAAI integration!
PPS. for VDI performance check attached whitepaper
0 Kudos
pgoggins
Enthusiast
Enthusiast

In looking at a DR site we had a single P2000 G3 node with 12x3TB midline drives in the unit and did the following split on the drives

  • 9TB raw (4x3TB Raid5) - P4000 VSA LUN
  • 9TB raw (4x3TB Raid5) -  P4000 #2 VSA LUN
  • 6TB raw (3x3TB Raid5) - Backup iSCSI target
  • One global hot spare

The pair of VSA LUNs are for DR replication only of the production P4000 cluster.

For now I would say calculate our how much disk space you will need, figure in any known growth numbers, add 20% if this is less than 1.5TB (8x450GB Raid10) then go Raid10, else go Raid 5.

----------------------------------------------------------- Blog @ http://www.liquidobject.com
0 Kudos
BharatR
Hot Shot
Hot Shot

Hi,

 What RAID option should we go with with 8 drives? I was thinking RAID 5  with 6 or 7 drives and the remaining drives setup as hot spares.

Here is the Overview of Supported RAID Implementations for HP P2000 G3 MSA

2063213.png

Best Practice for Creating the RAID is 5 and 10.

Best regards, BharatR--VCP4-Certification #: 79230, If you find this information useful, please award points for "correct" or "helpful".
0 Kudos
rickardnobel
Champion
Champion

darkbgr123 wrote:

RAID Type                           RAID10      RAID5          RAID6

Sequential Writes MB/s              850         1,350          1,100

A bit surprising that RAID5 got better write performance than RAID10.

My VMware blog: www.rickardnobel.se
0 Kudos
darkbgr123
Contributor
Contributor

Maybe because of too many spindles!

I just opened HD Tune out of curiosity on one of my VM;s and My personal results are 1500MB/s

www.picpaste.com/first_results_from_SAN-gDuVUMf1.png

0 Kudos
pgoggins
Enthusiast
Enthusiast

More spindles always helps. In your configuration your looking at the  write performance of four drives vs the write performance aggregate of 7  drives - parity. Raid 10 is used when you need the IOPS or when you  have large enough pools of disks that you would run into a larger issue  of cascading failures (12x3TB midline in a single Raid 5 scenario).

As far as the variations between tests are you both connected to the P2000 via the same medium? http://www.qdpma.com/Storage/HP_P2000.html has some generalizations on the protocol performance differences.

----------------------------------------------------------- Blog @ http://www.liquidobject.com
0 Kudos
raldridge254
Enthusiast
Enthusiast

We had a lot of problem with our P2000, the performance just wasn't as we needed it to be, replacing wasn't an option.

We moved over to RAID10 and have been really happy with it, as everyone says, the issue is the cost/waste losing half your disks however I believe if you're looking to use VDI later it will be well worthwhile using RAID10.

If you budget can stretch to one more disk, you can configure this as a Global Spare giving you some peace of mind whilst you wait for HP to replace the disk.

0 Kudos