Lukas Beeler's IT Blog

The i Blade is up and running, and i’ve received quite a bit of feedback on the Installing the JS12 Blade post.

In the meantime i wasn’t just wasting my time on trivial things such as getting actual customer work done, but also playing a bit further with the JS12 Blade.

I’ve installed the software my company produces (DIAS-iS) on the JS12 blade, and ran a few very unscientific benchmarks. But first let’s talk about the disk situation in with IBM i on a JS12 blade in a BladeCenter S (i really like those convoluted product names).

Managing disks under IBM i on a JS12 Blade

As i found out the hard way during the initial bladecenter setup, the JS12 blade only supports SAS disks, and can cause issues if you have SATA disks zoned to it.

There are a few important considerations when thinking about the IBM i/JS12/BladeCenter S combination: First off, disks are directly attached to VIOS, and then virtualized by VIOS for the IBM i as SCSI disks. It’s important to note here that you do not have any (supported) options of RAIDing the disks before the IBM i sees them. So all disks are mapped through 1:1 to the IBM i OS, and then mirrored using IBM i mirrored protection. This is entirely different from the approach you would use in a BladeCenter H with a FC attached SAN.

Just to be clear: There is no cache on the JS12 and there is no way to use any disk protection except IBM i mirrored protection. You can’t use RAID5, RAID6 or hotspares. You can’t VIOS mirrored volume groups either, because it’s unsupported.

I’m thinking about removing one of the disks from the BladeCenter in order to test how recovery from a disk failure would look like, but i’m afraid of wasting a lot of work that i’ve already invested in this system – i’ll try this shortly before i have to give everything back.

I’m not sure what the virtualization by VIOS exactly entails, but i would assume it’s fairly similar to what Hyper-V/ESX do when you create “Passthrough disks”. This probably means that things like Predictive Failure Analysis (PFA) will probably not work.

Another, rather obvious, drawback is that you cannot install any expansion cards (well, there is the odd one you can install into the blade). But it also means there is no Twinax, no SNA directly over Ethernet, no Modems, etc. Not a big issue for us, as we’re urging our customers to stay current on technology, but not everyone is an IBM i shop – there are still lots of AS/400 shops out there.

If you access the System i Navigators SST/Disk management function, it will not be able to help you with disk locations. I haven’t found out on how to call disk locations in IVM/VIOS, but then again i don’t really know much about IVM/VIOS.

Installing DIAS-iS on the JS12 Blade

I’ve installed our software without a hitch, and loaded our 30GB Test/Benchmarking database on it. I ran several benchmarks, and the JS12 with it’s four SAS 15kRPM 147GB Arms in a mirrored configuration and one core and 13GB RAM in the IBM i LPAR was a bit slower (less than 5%) than our System i515 with four U320 15kRPM 70GB Arms in a RAID5 configuration and 3.5 GB in the IBM i LPAR.

Unfortunately, i do not have a M15 to pit against the JS12, as these two would be using comparable technology. It would also be interesting to see an M15 with four 147GB SAS disks in a mirrored configuration to compare the systems 1:1, especially regarding disk performance.

Next steps to go?

What’s next? Well, Backup obviously. If you’ve read the i on Blade manual you’ll see that saving to tape will be interesting to say the least. I already have a TS3100 ready to go, but i’m currently missing a SAS for attaching it. As soon as i have the cable, expect a big post about saving and restoring.

Questions? Suggestions? Any specific questions about i on Blade? Want me to test something for you?

Leave a comment or drop me a mail. I’ll be happy to help.