Edit: Some links no longer work.
Originally posted January 24, 2012 on AIXchange
The December AIX Virtual User Group webinar featured Nigel Griffiths’ discussion of phase 2 of shared storage pools. If you didn’t tune in, download the presentation materials and listen to the replay.
The new shared storage pool functionality is enabled with the latest PowerVM 2.2 service pack, and is a feature of PowerVM Standard and Enterprise. If you already have PowerVM, simply download the VIO server fixpack to obtain these new features. (Note: Because this TL is based on AIX 6.1 TL7, your NIM server must be at AIX 6.1 TL7 or AIX 7.1 TL1 to use your NIM server with your VIO server.)
One thing to note, as Nigel points out in the presentation, is that the most common VIOS storage options have been around for some time:
1) Logical volumes, created from a volume group and presented to client LPARs
2) Whole local disks
3) SAN LUNs
4) File-backed storage, either from a file system on local disk or a file system on SAN disks
5) NPIV LUNs from SAN
Nigel then discusses the newest option: using SAN LUN disks that are placed into a shared storage pool. This new option, he emphasizes, doesn’t eliminate any of the other options. It does not portend the death of NPIV. It’s just an additional VIOS storage choice we now have.
Listen to the replay or look over the slides to gather Nigel’s thoughts on the benefits of shared storage pools. He explains that fibre channel LUNs and NPIV can be complex. They require knowledge of the SAN switch and the SAN disk subsystem. If you need to make changes, it might take your SAN guys awhile to implement them. This can slow overall responsiveness. That’s to say nothing of smaller organizations that don’t have dedicated SAN guys. Live partition mobility can be tough work if your disks aren’t pre-zoned to the different frames.
With a shared storage pool you pre allocate the disk to the VIO servers. Then it’s under your control. You can more easily allocate the space to your virtual machines.
POWER6 and POWER7 servers (including blades) are needed to use shared storage pools. At minimum you should allocate a 1 GB of LUN for your repository and another 1 GB of LUN for data, but in order to be useful, in most cases you’ll need much larger LUN(s) – think terabytes of disk — if you plan to do much with it.
Your VIOS must have the hostname set correctly to resolve the other hostnames. In Nigel’s experience he couldn’t use short hostnames — they had to be changed to their fully qualified names.
He also recommends giving your VIOS a CPU and at least 4 GB of memory. “Skinny” VIOS servers aren’t advisable with shared storage pools. Currently, the maximum number of nodes is four, the maximum physical disks in a pool is 256, the maximum virtual disks in a cluster is 1,024, and the number of clients is 40. A pool can have 5 GB to 4 TB of individual disks, and storage pool totals can range from 20 GB to 128 TB. Virtual disk capacity (LU) can be from 1 GB to 4 TB, with only one repository disk.
If you played around with phase one, you’ll find that many of your limits have been removed. Now you can use shared storage pools for live partition mobility, perform non-disruptive cluster upgrades and use third party multi-pathing software.
You cannot have active memory sharing paging disks on shared storage pool disks.
Nigel covers the relevant terminology (clusters, pools, logical units, etc.). He also demonstrates how to actually prepare and set up your disks. In a nutshell you must get your LUNs online and zoned to your VIO servers, and you need to set your reserve policy to no_reserve on your LUNs.
After covering the commands for managing clusters — cluster –create, cluster –list, cluster –status, cluster –addnode, cluster –rmnode and cluster –delete — he recommends creating the cluster on one of the VIO servers and then adding additional VIO servers to the shared storage pool cluster. From there, you can allocate space to the VM clients.
Next week I’ll have more information from Nigel’s presentation, including scripts and cheat sheets. In the meantime, why not upgrade your test machine’s VIO servers to the latest level so you can try this functionality?