Product Reviews

IP SANs continue to strengthen their position in the SMB network storage market, as they offer clear cost benefits over expensive fibre channel (FC) SAN solutions. IBM now moves in with its latest System Storage appliance and, in this exclusive review, we take a closer look at the DS3300 Express, which aims to give SMBs an affordable entry point into network storage consolidation.

This is IBM's second stab at iSCSI, and it started 2007 without a solution after it ended its relationship with Adaptec. The DS3300 represents a strengthening partnership with LSI Logic, since it's based on the latter's Engenio 1532 array. The DS3300 comes as a 2U rack chassis, with room for up to 12 hot-swap SAS drives mounted in the same sturdy carriers employed by IBM's servers.

IBM offers two Express models; we were supplied with the version that has both controllers installed. These are mounted in easily removable sleds and equipped with a 667MHz Intel XScale processor teamed up with 512MB of battery-backed cache and a SAS expansion port. The host ports are also partnered by an embedded TOE for improved iSCSI performance and, unlike Dell's PowerVault MD3000i, you can upgrade the cache in each controller to 1GB.

Expansion options are also better than Dell's, as the DS3300 supports up to three of IBM's EXP3000 cabinets, allowing capacity to be expanded to include up to 48 hard disks. Another bonus over Dell is that IBM has already confirmed support for SATA hard disks. Note that you can't use your own choice of disk, as these must be sourced from IBM. With a pair of controllers in the mix, you have a range of options for link failover and redundancy. Choices include a redundant two-node cluster, attaching four host systems directly to each port or adding an ethernet switch and providing a high-availability storage solution for up to 16 host systems.

Initial installation is handled by the bundled Storage Manager 2 Client utility (SMC2). Just connect the appliance's ethernet-management ports and run the

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discovery routine, which locates the system on the network. It will offer to configure the drives for you, where you can choose from RAID0, 1, 3, 10 or 5 and leave SMC2 to select the drives and create an array. For each host system, you need to install the Storage Manager client components, which include IBM's DSM (device specific module). This supports Microsoft's MPIO (multi-path I/O) for creating redundant paths from hosts to storage volumes, so if one controller fails the drive will be reassigned to the other controller. Don't use Microsoft's MPIO driver instead of IBM's DSM, as there's no guarantee it fully supports the appliance.

If you plump for manual logical drive creation, choose an array type, the drives to be included, and decide on the number of virtual drives and their sizes. You can then declare your host systems to the appliance, but, as with the DS3200, we found the automatic function failed to find our test systems. This wasn't a major issue, as we just used the manual host access tool, where the logged-in initiators were correctly identified. As each host is assigned a logical drive, you can decide how much space it can use and whether or not it will share this with other hosts. You can also place multiple hosts in groups that share the same mappings. Called partitioning, the base system supports only two partitions, but you can license up to 16.

IBM also offers the optional Snapshot and Volume Copy features. We found these easy to use and, for the former, you simply select an array, choose a destination, decide what percentage of space the snapshots should occupy and elect whether to map it to a host. The Volume Copy works well and is handy for creating backups, moving data to a larger array or restoring data from a snapshot.

For performance testing, we installed the DS3300 in the Labs' gigabit network and direct attached three Windows Server 2003 R2 systems loaded with Microsoft's iSCSI initiator 2.05. With one server logged into a dual-drive RAID0 stripe, we saw the Iometer utility reporting a speedy raw read rate of 112MB/sec. With the second server direct-attached and using its own dedicated RAID0 stripe, Iometer reported a cumulative read performance of 221MB/sec. With three servers in the mix and all using their own dedicated virtual disks, performance settled to an impressive 276MB/sec.

Comparing our test results with those of the MD3000i shows there's nothing between Dell and IBM for performance. However, IBM wins the day with its support for both SAS and SATA drives, the RAID cache memory upgrade options and a superior expansion potential.