IanHF talked recently about LUN sizes and establishing standards across the enterprise. The choice of LUN size is a subject I’ve bored people with ad nauseum over the years and this is a good opportunity to go over it again.
Ian’s post goes into more detail than the scope I intend to cover here. In fact, all I’m concerned with is LUN size. I don’t mind if it’s 1GB or 100Gb as a standard (well, I do, but that’s another post), all I care about is keeping a consistent LUN size across vendor technologies. Here’s why.
Host Based Migration
None standard LUN sizes mean host-based replication. It means using tools at the host level (like Veritas Storage Foundation) to restructure the data onto new LUNs. Worse, it could mean simply bulk copying of data at the host level, with outages to boot.
Here’s my advice. Pick a consistent LUN size. Choose one that works across all of your storage platforms at the block level, so when you want to move data by virtualisation or other vendor tools, you can achieve it without having to restructure the data.
I’m involved again with a client/customer I left about 3 years ago. At the time, I recommended taking the hit and migrating their disparate infrastructures to a consistent LUN size. They didn’t take my advice and they still have the same LUN size pain points they did 3 years ago. It means the migration process to move off old technology is more complex and expensive than it needs to be.
It’s amazing how such as simple change can be so impactful and how many organisations choose to ignore it.