Easy Tier - what you might not know about Auto Rebalance

I thought I knew quite a lot about DS8000 and Easy Tier but last week I had the opportunity to meet Stephen L. Blinick who works at the DS8000 labs in Tucson. Stephen is closely engaged in the development of the DS8000 box. And he's a great presenter who (obviously) knows what he's talking about.

There was one aspect about Easy Tier Stephen told me of which I was completely unaware. I should have known because this is somethning really important about Easy Tier and its Auto Rebalance feature. As the Redpaper 'IBM System Storage DS8000 Easy Tier' states : "The auto-rebalance capability automatically rebalances the workload even across the physical resources within a drive tier, reducing the occurrence of hotspots".

So, as you see below this is a situation within a drive tier where Easy Tier detects some hotspots.

 It rebalances the workload across all ranks.

By doing so, auto-rebalance reduces performance skew within a storage tier and provides the best available I/O performance from each tier.

But there's more and here comes the interesting part of the story. You know how it's always so annoying when you add additional ranks to the pool. Everything is well balanced within the existing ranks but you have to put new workload just on the new disks or you have to rebalance everything manually. NOT SO with Easy Tier.

"Auto Rebalance also automatically populates new ranks that have been added to the pool when rebalancing the workload within a tier. Starting with DS8000 R6.2 LMC, auto-rebalance can be enabled for hybrid and homogeneous extent pools".

Great ! Isn't it ? Check out the Redpaper if you want to know more about this great feature.