Expanding a P4300 cluster

[M. N.]

A customer is using a P4300 cluster made up by 4 nodes (storage systems).

The cluster is confngured with 2 LUNS that are almost full and provide storage to a VMware vShpere cluster.

They want to add 2 additional storage systems to the existing cluster without powering off the existing storage systems.

Is there any document or best practice they can refere to?

Given the 2 new storage systems will be added to the existing cluster, should they expect the cluster to reallign slowing down for a long time (hours or days)?

How can they avoid such allignment (mainly, how can they avoid to slow down the cluster after expanding it)?

Regards

marius

[oikjn]

you can add nodes to a cluster online without downtime to your SAN.  It DOES require a cluster restripe as the SAN realligns to take advantage of the new storage space.  How long this takes depends on a number of factors.  You can control the rate this happens in the properties of the management group by limiting the bandwidth dedicated to cluster tasks (aka LUN restripes).  You can let it run at full bandwidth, but that will kill LUN performance and is best done only if you dissable lun activity during that period, or you can make it run any other speed you want.  Basically you can just monitor your volume latency and que and adjust the speed to as fast as you want as long as you are happen with performance.  

Just an FYI, you don't HAVE to have an even number of nodes.  You can add a single Node to the cluster and it will add its capacity to the cluster just fine.  If they need the space from two nodes then they can add two at one time, but it isn't required.