IBM System Storage DS3512 Express review

Dave Mitchell Read more December 8, 2010

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£3331

Price when reviewed

Network storage arrays aimed at SMBs are invariably offered with only SATA hard disks to keep costs down. IBM’s latest System Storage DS3500 family brings 6Gbits/sec SAS within their grasp, and here we put the DS3512 through its paces and see whether compromises have been made in the search for value.

The DS3500 family consists of two head unit options, with the DS3512 on review supporting 12 3.5in drives. The DS3524 is also a 2U appliance, but can handle up to 24 2.5in disks; prices for this start at £3,087. Both models have a single controller that can be upgraded with a second where they run in active/active mode.

IBM gets the value ball rolling: along with standard SAS and full disk encryption (FDE) SAS drives, it also offers near-line SAS. These new drives deliver the high capacity and low cost of SATA but with SAS drive electronics. Offered with 7.2k spindle speeds, they do away with the need for a SATA-SAS interposer, so reducing manufacturing costs and potential failures. They also have the same level of host queueing support as standard SAS drives.

The DS3500 controllers offer plenty of connection options. You start with a pair of fixed 6Gbits/sec SAS ports for DAS applications, but there’s room for a daughtercard, and IBM offers dual-port 6Gbits/sec SAS or quad-port 8Gbits/sec Fibre Channel and Gigabit iSCSI options. Our review system came with the 8Gbits/sec Fibre Channel card.

Expansion potential is based on the drive count, not the number of shelves. Each controller has an embedded 36-port SAS expander linked to its expansion port, so a pair can support up to 96 hard disks. You can daisy-chain as many shelves as you like, as long as you don’t go over this number of drives.

You can mix and match IBM’s EXP3512 and EXP3524 expansion shelves, join them with multiple redundant SAS paths and have different SAS drive types within the same shelf. The controllers have 1GB of cache, but the battery backup plays a different role to what it usually does. In the event of a power failure it keeps the controller running, so cache contents can be de-staged to an on-board 8GB SD memory card.

Deployment in the lab was simple, courtesy of IBM’s Storage Manager 10 Client (SMC10) utility. This kicks off with a discovery routine that searches the network for storage arrays, displays them ready for configuration, and presents plenty of wizards.

Your first job is to create RAID arrays, and SMC10 offers plenty of assistance on the best choices. It also checks all the physical drives and separates them in the main interface based on capacity, interface and spindle speeds for easier identification.

You can take manual control where you select an array type, choose the member drives and decide whether to set any aside for hot-standby duties. SMC10 validates your choices, offering to carve up the storage space into equal-sized logical drives.

Logical drives are then mapped to hosts; SMC10 automatically identified our test servers connected to the controller via 8Gbits/sec Brocade Fibre Channel HBAs. During this phase you can decide whether a host has dedicated access to a logical drive or shares the mapping with others.

Shared host access to logical drives is controlled by host groupings, or partitions. The system comes as standard with support for four partitions, which can be increased to 64 using IBM’s premium feature upgrades.

Remote mirroring isn’t supported on the older DS3000 series of appliances, but this is now available, allowing you to replicate appliances over their Fibre Channel ports. Logical volumes can be resized on the fly, while dynamic capacity expansion allows you to drop in more disks or expansion shelves and add them to existing logical drives.

For performance testing, we started with a Broadberry CyberServe dual Xeon X5560 server running Windows Server 2008 Enterprise R2. We mapped it to a dedicated volume and saw Iometer report a fast 648MB/sec raw read throughput. We then added a Dell PowerEdge R715 dual Opteron 6100 server and mapped a second dedicated volume to it. With Iometer running on both systems we saw a cumulative raw read throughput of 1,280MB/sec.

IBM’s DS3512 Express delivers a fine blend of SAS storage: performance over 8Gbits/sec Fibre Channel is beyond reproach, and redundancy levels and expansion options make it highly versatile.