Roger Howorth

Experts say that we'll continue to spend more on storage than on servers in coming years. And EMC's acquisition of virtual server specialist VMware seems to show the storage giant is confident about sales.

It might look like an odd fit, a storage vendor buying a server software firm, but the link between storage and virtual server systems will probably become one of the main drivers of demand for storage management systems.

For example, we recently installed VMware's ESX Server virtualisation tool to partition IT Week's trusty four-way lab server so that it can run eight or 10 operating systems simultaneously.

We do have a few Windows 2000 Servers, but mainly it's Linux systems, each running DHCP, DNS or some other LAN infrastructure application.

It turns out that the relatively old processors are fast enough to handle this load, and the virtualisation software can divvy up the RAM so it's allocated dynamically to the systems that need it most.

The problem has turned out to be the server's Raid array and its old 9GB SCSI disks. The Raid 5 array's capacity of around 47GB is barely enough for that number of operating systems, and the performance is poor - it seems to write data at a maximum rate of about 2MB/s.

So after years of making do with the original Raid array, it's almost time to upgrade the disk drives. In these times of tight budgets you might not be surprised to hear that our solution is to replace some of the old mechanisms with new 150GB ones.

Luckily the Raid controller is smart enough to allow individual disk drives to be retired from the array. The controller will rebuild the Raid array so that the data ends up safely stored in such a way that a failure of one of the remaining disk mechanisms would not result in data loss.

The plan is to convert the six-disk Raid 5 array so it ends up as a mirrored pair, and replace four disks with the new ones.

As is so often the case, the main problem turns out to be the cabling. We have ended up with disk drives that have separate SCSI and power connectors, and our server's disk trays are built to take drives that use the combined SCSI and power connector.

Anyhow, having upgraded our storage hardware, we'll still need to look at ways to back up the data on it, preferably without taking the virtual servers' hard disks offline.

This is where storage management systems could come in really handy. Many firms already have storage area networks (SANs) of some kind, but I reckon it won't be long before everyone uses server virtualisation tools, and at that point everyone will need a SAN with proper management tools.

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