Dell EqualLogic PS4100E review

Dell’s latest EqualLogic IP SAN appliances represent the biggest platform refresh since they were acquired in 2008, including a major hardware redesign. A big change that affects the entire range is the move to in-house manufacturing. This has allowed Dell to slash prices, making the entry-point appliances more affordable for SMBs.

The PS4100 family is aimed at SMBs and enterprise offices, and in this exclusive review we examine the entry-level PS4100E. It supports 12 hot-swap nearline SAS drives, and the price for this system includes a full house of 1TB drives. Another version offers 15K LFF SAS drives, and the PS4100X and PS4100XV models support 24 10K or 15K SFF SAS drives respectively.

The controllers have been redesigned and have an uprated 6Gbits/sec SAS backplane, plus Dell’s new cache-to-flash feature. Battery packs have been replaced with a capacitor, and in the event of a complete failure it provides enough power for the cache to be written to flash memory.

Cache contents are synchronised between the controllers, which also show off Dell’s vertical port failover feature. If a port in the primary controller fails, it will use the corresponding port in the secondary controller. The PS4100- series controllers have dual Gigabit data ports and a dedicated 10/100 management port. If you want high-speed 10GbE ports then check out the PS4110 series.

A key concept of the EqualLogic appliances is grouping. Although each looks after its own RAID arrays, the storage on all group members is available as a single entity. Volumes created in this space are presented as iSCSI targets, but data is spread across all members. Group membership is restricted to two appliances, so the PS4100 series has a top capacity of 72TB per group. If you want to grow your group beyond this point you must add a PS6100 series appliance, which lets you expand group membership up to 16 S4100 and PS6100 appliances.

The Gigabit data ports are grouped together under a virtual IP address and load-balanced. Add a second appliance and its ports join the virtual IP address, increasing available bandwidth.

Dell’s Remote Setup wizard finds new arrays and guides you through RAID and group creation. Further management options await in the Group Manager or SAN HQ consoles, and role-based access includes AD authentication.

During volume creation, you pick a storage pool, choose a size and apply access restrictions based on CHAP authentication, IP address or initiator name. You can enable thin provisioning as well, which uses three watermarks to manage volume usage and alert you when spare capacity gets low.

Snapshots are included in the price, with up to 128 per volume and a total of 2,048 per group supported. You can group selected volumes together and apply one snapshot schedule to them all.

Replication is a standard feature, storing snapshots of selected volumes in separate groups. You can choose one-way replication to another group, bidirectional replication or designate one group as a central location to which multiple groups are replicated.

For testing, we used a Dell PowerEdge R710 rack server equipped with dual 2.53GHz Xeon E5540s and running Windows Server 2008 R2. We logged the server onto the group’s virtual IP address to enable load balancing and connected it to a 50GB virtual volume.

Dell’s host integration tool (HIT) makes MPIO configuration a breeze: log on to the portal and leave it to sort out the details for you. Performance is good. With the Iometer benchmarking app configured with four disk workers and 64KB sequential read transfer requests, we saw a high raw read throughput of 235MB/sec.

For general SQL database performance testing, we used 256 outstanding I/Os, a 16KB block size, 66% read, 34% write and a 100% random distribution. Iometer settled down to a steady 5,770 IOPS, easily enough for SMB-level database operations.

The PS4100E is a breeze to deploy, with Group Manager and SAN HQ apps simplifying ongoing management. Along with fine performance, you get snapshots, thin provisioning and replication included. It’s a successful refresh.

Author: Dave Mitchell