No more virtual fubar

31 01 2008

To cut a long story short, my test data was ok. It was how Linux LVM handled the presented disks when I virtualised them, or to be more precise, the order in which they were presented. One of the tests I was doing was to see if it was important to re-advertise the disks after they were virtualised behind the NSC, so I had not presented them in the same order. When I re-virtualised the 9980 disks the third time, I presented them to the NSC in the same order as native to the linux host, and presented them as external Open-Vs. I presented them in that same order from the NSC to the Linux host, and Bob’s your relative, data was accessible and all was dandy. Brown trousers averted!

I then re-created the experiment from the USP-100 that I’m actually going to be migrating data from soon (before you jump up and down and shout ‘a USP to NSC/AMS – are you mad?’ – the answer to which is ‘occasionally’ – this is development data that should not have been there to start with). This time the presented disks are 14Gb Open-Vs, same size as formatted on the NSC and its production external storage on an AMS-1000. That worked a treat, and then I used shadowimage to replicate the data from the virtualised USP-100 through the NSC and out to the virtualised AMS, then re-presented that to the Linux host.

So there you have it. You don’t need to fork out for tiered storage manager (HDS – stop calling it TSM – it’s confusing, there’s already a TSM out there. I know it’s supposed to be called HTSM, with one of the characters in lower case, but everyone always forgets the ‘H’!) if you have a Shadowimage licence. You will need a couple of application outages to do a migration this way, but it can be done and timed to minimise the inconvenience to nothing.

Don’t forget the gotchas: present the old storage out as Open-Vs, and make sure your destination Open-Vs are the same size for Shadowimage to work; make sure you know whether or not the host O/S will need to have the virtualised old disks and subsequent new disks presented in the same order (probably not an issue with Veritas, for example); test, test and test again! I’ll be replicating my testing on AIX, Solaris and HP-UX, some with Veritas, others with native LVM. I’ll let you know how I get on.

Off to pick up the children now from nursery and after school clubs. Expensive business, childcare, and Gordon **** Brown just doesn’t help out enough with the tax breaks. It’s not so bad in the Midlands, but in London it cane cost £800 – £1000 per month for a child when the parents work full time, and a £55 / week tax break is a pathetic pittance. Oh how I wish he’d called that election a few months ago. Can’t wait to see him on the opposition benches. 

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