Network storage at the enterprise level has always commanded premium prices and nowhere more so than with fibre-channel SAN arrays. The latest iSCSI specification looks a fine remedy as it can reduce costs significantly by using your existing Ethernet infrastructure. But even here the price tag puts these arrays beyond most small to medium businesses. As weve seen with firewalls, the latest software-only products offer a cost-effective alternative by allowing you to use your own hardware. So it is with SANmelody which turns a standard Windows 2000, XP or 2003 system into a storage array that supports both fibre-channel and iSCSI connections.
Hardware requirements for the storage server are reasonable with a minimum specification of a 300MHz processor, 512MB of RAM and 65MB of storage and it supports any external or internal storage device that Windows can work with. Initial installation on a Pentium III 866MHz system running Windows 2000 Server only took a few minutes and we opted to test iSCSI functionality as this will appeal to SMEs as it is most cost-effective solution. At this stage SANMelody loads its own iSCSI target drivers for each active network adapter and if you have the optional support for fibre-channel itll load drivers for any resident HBAs as well. We did encounter a few problems at this stage as the iSCSI driver for our Intel Gigabit network card frequently refused to start after a reboot and without these SANmelody wont create new iSCSI channels. We had to keep reinstalling the driver and restarting the system which eventually loaded it correctly.
SANmelody installs as an MMC (Microsoft management console) snap-in and is accessed from the Computer Management utility so its easy to keep an eye on the software, drivers and hard disks all from the same interface. Partitions on your shared drives need to be prepared from the Disk Administrator as unformatted basic disks with no drive letters assigned. Systems that are to access the drives are termed application servers and we used four Pentium III and dual Xeon based Windows systems with Microsofts iSCSI initiator installed. These need to be logged on to the storage server which will display each iSCSI connection as an available channel. Application servers are then declared to SANmelody but note that at this stage these objects do not have any physical reference to the servers. From the objects properties you then browse available channels and assign them to the correct server object so clear initiator naming conventions will make this easier.
Each partition is declared as a virtual volume with is then mapped to selected application servers. We did find we needed to log the iSCSI initiators off and back on to the target but afterwards the volumes appeared to each server as standard local hard disk which could be formatted from the Disk Administrator. These can be dedicated to one server or shared amongst many and once a formatted partition has been created on one system it will become available to all others that have a mapping to it.
To test raw throughput we used the open source Iometer utility which reported some impressive results. With all four application servers sharing a single volume over Gigabit Ethernet we saw an average of 27MB/sec for each one with 100 per cent sequential read operations. We then created four separate virtual volumes on the same 70GB Ultra320 SCSI drive on the storage server and dedicated one to each application server. With the same settings Iometer returned average transfer rates of 45MB/sec for reach server for cumulative total of 180MB/sec. As SANMelody works alongside Windows you can use the storage server for other purposes but dont expect any great results as all Iometer tests generated close to 100 per cent processor utilization.
Although we didnt completely resolve the problems with the iSCSI drivers we still found SANmelody to be a slick storage alternative capable of delivering an impressive performance over iSCSI. The price for the package on review includes support for iSCSI, eight volumes and two channels but it can be expanded to include FC support and other options such as failover making it a highly scalable product that can grow easily with demand.
Comparing this software-only solution to the current crop of FC and iSCSI disk arrays shows you can make some big savings by using your own hardware. Performance over iSCSI is just as good, you can easily add your own fault tolerance and the options available make this a very scalable solution.