by Joe Gleinser
14. October 2009 19:47
Most of our clients choose between an Entry Level or Mid-Level SAN, as described in Part 1 of this Buyer's Guide. In this post I'll identify the features that differentiate those two classes of SANs.
Clustering: Clustered SANs operate like clustered servers. If one fails the other takes over immediately. This is only available in the Mid-Level products such as HP Lefthand, Dell Equallogic, etc. Only HP's Lefthand offers true clustering out of the box. The minimum order for a Lefthand SAN is two completely separate units.
Thin Provisioning: Mid-level SANs allow you to oversubscribe storage by allocating storage to a volume without reserving that storage. If you create a 100GB volume but only use 40GB, the remaining 60GB is free to be allocated to another volume. This feature is essential in maximizing the storage efficiency of a SAN.
Offsite Replication: Replication between SANs is the foundation for an excellent DR solution. Replicate all data and VMs to another site. Many of the mid-level SANs offer this solution but in some it is a licensed add-on. HP's Lefthand includes scheduled replication at no additional cost but real time replication and automated failover is an additional license fee.
Snapshots: Snapshotting technology is an on-array backup method that utilizes a relatively small amount of disk space. This is possible to restore entire volumes quickly without relying on external storage.
De-duplification: Long an enterprise only feature, integrated de-duplification is making its way into mid-level SANs. This can dramatically increase the efficiency of storage but can have a significant performance cost.