After writing up this post on FAST VP INYO Goodness last night, I went to delete my notes I had taken on the IPAD and realised I’d forgotten one very cool new feature which may have slipped under most people’s radar.
When creating a LUN from a FAST VP enabled pool in the current version of FLARE, you have the following options to select from.
- Highest Available Tier
- Lowest Available Tier
These of course are Auto-Tier policy’s; selecting one determines which algorithm is used to distribute data through promotions and demotions of 1GB slices between storage tiers.
At LUN creation time I refer to these as “Initial Data Placement” policy’s, a term which I’ve actually taken from one of the VNX best practice documents found on PowerLink. Each policy directly impacts which storage tier the data is first allocated to.
The Highest and Lowest options are self-explanatory; Auto-Tier unless I’m mistaken uses an algorithm to distribute the data over all available storage tiers which in my opinion increases the risk of having performance issues before the pool has had sufficient time to warm up.
When you create a LUN, you’ll find that Auto-Tier is actually the default selection, however I always change this to Highest Available Tier to ensure that data starts off on the highest performing disk and once the migration of data is complete I switch the policy to Auto-Tier to let FAST work its magic.
But Now…… INYO introduces a new policy
- Start High, Then Auto-Tier
The introduction of this policy effectively means I no longer have to go and remember to do this manually. While some might think this is a non event in terms of new features, to me its a good example of how FAST VP is evolving based on feedback from partners and customers…. and that I like.
Performance and efficiency of data is all about the locality of the data, if you’re migrating data from an older storage array to a VNX, the last thing you want is for people to complain about performance. Although Auto-Tier is the default option when creating a LUN, the option Highest Available Tier is the policy recommended in the best practice documentation.