Dell EqualLogic PS4000E review

Dell's latest member of the EqualLogic family of IP SAN appliances, the PS4000E, aims to offer a more affordable alternative for medium-sized businesses. Not only does it deliver an impressive range of features but it could be one of the fastest appliances in its class.

The PS4000E supports a pair of controllers, and Dell offers a range of options to allow you to grow with demand, by opting for one or both controllers and either eight or 16 SATA drives. Each controller has two Gigabit data ports and a management port, and comes with 2GB of battery-backed-up cache and support for RAID6.

Physical appliances are gathered together in groups and presented as logical storage pools. Virtual volumes are created within these and presented as iSCSI targets, but the volume data is spread across all appliances and drives in the group. Note that the PS4000E is restricted to two appliances per group.

Installation is simple thanks to Dell's Windows Remote Setup wizard. You choose a member name and assign it an IP address, pick your RAID array and join an existing group or create a new one. The two data ports are grouped together under a virtual IP address where the appliance carries out load balancing.

Dell's Group Manager console provides easy access to functions such as group, storage pool and volume creation. For the latter you choose a storage pool, decide on a volume size and add access restrictions. Thin provisioning can be configured during volume creation and you decide how much physical space to start with. The appliance uses three watermarks, where the minimum size is 10% of the virtual volume. When the volume is 95% full the system starts throttling back I/O performance to allow administrators time to increase the volume size. Once you reach the critical watermark the volume is placed offline.

With snapshots you decide how much space to set aside, and at any time you can promote snapshots as new volumes. A thin provisioned volume will have its snapshots and replicas thinly provisioned, and you can swap between classic and thin provisioned volumes.