SQL Server
As I mentioned in an earlier blog, I was testing out access to a Virtual SAN using iSCSI. iSCSI is a relatively new technology that enables accessing a SAN over TCP/IP. Let’s take a look… Storage Area Networks traditionally have been accessed using the fast and reliable Fibre Channel Switching (FC-SW) architecture. Very fast, very reliable and very expensive. This replaced the old SCSI cabling which had a maximum specification of 25 metres. The Fibre cabling could max out at 10km across a city if necessary. Very Very expensive. Your server would need an HBA (Host Bus Adapter) and Fibre switches and cables to form the “Fabric” between the Host Server and the SAN. The Fibre Channel effectively transports SCSI commands and fools your server into thinking the SAN is connected locally. Now with the advent of the open iSCSI protocol, we can use existing TCP/IP networks to transport SCSI commands even over the internet. This may not be as fast or as reliable as Fibre but it certainly is cheaper and you may be surprised how close the performance comes using Gigabit Ethernet adapters. You can use the software-based Microsoft iSCSI “Initiator” which allows you to connect to a “Target” LUN on the SAN that will access many spindles for performance and redundancy. Your server just sees the disk as another drive and again is fooled into thinking it is local even though it may be many miles away. The SAN provides all the RAID features you would need along with extra memory, CPU and caching. All transparent to the host server. The SAN will also do background replication and snapshots if you wish, independent of SQL Server. If you need extra performance, it is recommended to go with a hardware based iSCSI HBA on the host server since this will take the strain off the host server’s CPU given the extra TCP/IP processing but the software initiator works just fine for testing SAN access. Microsoft iSCSI Software Initiator Version 2.08 Download: http://www.microsoft.com/downloads/details.aspx?familyid=12cb3c1a-15d6-4585-b385-befd1319f825&displaylang=en cheers Brian
