The build it yourself Promise and DataCore system represents how far you can go on a tight budget if you're willing to roll up your sleeves. The Promise vTrak E610f is a 16-drive enclosure that includes two 4Gbps Fibre Channel controllers that offer RAID levels 0, 1, 0+1 (or 10), 5, 6 (double parity drive), 50 (two mirrored RAID 5 volumes), or 60. You can add up to three additional enclosures via Serial Attached SCSI, all using the same dual controllers or as many Fibre Channel dual controller systems as your switch will support. The Promise system doesn't include drives, you add your own SAS or SATA drives. Installing drives is straightforward and shouldn't bother anyone with hardware experience. There's even a full paper manual that fully documents the process.

Once the drives are installed, connecting to the system and initialising the RAID set or sets is straightforward. I installed eight Western Digital Raid Edition 500GB SATA drives and eight Seagate Savvio 15,000-rpm 73GB SAS drives, creating a 280GB RAID10 volume with the Savvio drives and a 3.5TB RAID5 volume with the Western Digital drives.

The next step was installing the DataCore SANmelody software on an HP ProLiant ML370 G5 server. I didn't count the server in the cost of the system for two reasons. First, the server is still available for other uses, and second, a really expensive high powered server is not required. SANmelody can even run on a VM. The server I used had a two port QLogic 2Gbps HBA connecting it to the Promise array, but SANmelody will work with any storage the server can see, whether direct-attached SCSI, internal storage or external, and can then make that storage available to other systems via Fibre Channel, iSCSI, or even Fibre Channel over Ethernet (FCoE).

Further, SANmelody provides the full set of storage management capabilities found in any of the other systems (apart from Pillar Data's application aware automation), such as thin provisioning of volumes, snapshots, and synchronous and asynchronous replication. In addition, I configured automatic migration of data from the RAID10 high-performance volume to the high capacity RAID5 SATA volume, essentially using the 15,000rpm high speed drives as cache for the SATA volume.

SANmelody also offers a plugin for the VMware Infrastructure and vSphere clients. This lets you perform any storage related task, including creating volumes, cloning existing volumes, and expanding disks from within the VMware management console. You can also download a free evaluation version of the software that will support up to a terabyte of storage.

With a total price of less than £6,000 for a full-featured storage system with 3.5TB of usable disk space and very high performance due to the 15,000rpm drives, why would anyone pay more for a storage system? Peace of mind and simplicity of installation are the primary reasons. You have to build this system yourself, and if something goes wrong, there is no single throat to choke. You could have several different vendors pointing fingers at each other. One other issue is the speed of the SANmelody management system. The process of coalescing multiple snapshots into a single new volume, which took from a few seconds to about a minute with the other systems I tested, took nearly 20 minutes for this system to complete.

I expect that SANmelody's volume unification depends on the speed of the Windows server hosting it. The system I installed SANmelody on had one single core 2.8GHz CPU and 2GB of RAM. By comparison, the Compellent controller has dual Intel Nehalem processors and 32GB of RAM, and is probably handling some operations with dedicated hardware.

If you're willing to invest the time in making sure the components are all correct, and in getting all the separate parts working together, the Promise-DataCore system offers a huge bang for the buck and great virtualisation support to boot.

OUR VERDICT

If you're willing to invest the time in making sure the components are all correct, and in getting all the separate parts working together, the Promise-DataCore system offers a huge bang for the buck and great virtualisation support to boot.