I have been working with iSCSI and storage area network (SAN) systems in the lab recently. The first challenge was to find a way to use our five-year-old Clariion Fibre Channel disk array. Unfortunately, we acquired the unit just as its manufacturer was taken over by EMC.
When EMC updated the Clariion range it changed the CPUs in the Raid controllers from PowerPC to x86-based processors. EMC was unwilling to back-port new software so it could be used with old hardware, and yet we wanted the latest software so that we could use the new storage management and virtualisation tools.
Happily, VMware's server virtualisation software came to our rescue, because it enabled us to connect the Clariion array directly to the server we use to run VMware. In turn, the VMware tools virtualised access to the disk array so that the virtual disks used by our virtual servers were actually stored on the Clariion array.
Each disk partition used by a virtual server is in fact one file in the host server's file system, so migrating the virtual servers was simply a matter of moving these files from the direct-attached storage to the Clariion array. An added benefit of this type of virtualisation is that we did not need to reconfigure the virtual servers after this move.
Well, it took about half a day to move the 10 virtual server partition-files from the direct-attached storage to the Clariion. But once this was done, we quickly developed an appetite for networked storage and decided to provide the same resources to our rack of blade servers.
Unfortunately, blade servers don't have PCI slots, so adding Fibre Channel cards and connecting them to our SAN posed a problem. Luckily iSCSI came to the rescue, because it enabled us to build an iSCSI storage server - called an iSCSI target device - that we could attach to the Clariion. We actually built the iSCSI target as a virtual server.
The main problem we had was in obtaining reliable iSCSI target software. Until recently, if you wanted to test iSCSI targets, Linux was about the only way to go. There are several open-source projects available from Sourceforge.net, but if my experience is anything to go by, you probably need to be pretty good at fixing compiler errors to get the open-source stuff to work correctly. Linux experts probably do this in their sleep, but not I.
So our iSCSI target project stalled because of errors caused by incompatibilities between the version of Linux used by the developers and the version we used in the lab - Gentoo Linux, which does not come with any support for the iSCSI project I was using.
Fortunately, we came across a beta version of a new DataCore product that can transform a Windows server into an iSCSI target. The new suite is called SANmelody and is reviewed below. DataCore will launch the software at the Cebit show later this week. As the first easy-to-use iSCSI target I have come across, it really is ground-breaking stuff and worth a closer look.
