iSCSI, ATTO and Overland

(Imported from rocketcat-v2)

I've been doing a bit of research about iSCSI and it looks like it's something that we're going to be seeing more of.

Basically, iSCSI is a method of running the SCSI command protocols over a TCP/IP network. This means that the SCSI commands and data are packaged up (and optionally encrypted) and placed inside a TCP/IP packet. iSCSI doesn't run at the lower ethernet level, but uses the existing TCP/IP stack to communicate. The advantages of this is that in order to set up a SAN, you don't need expensive Fibre Channel switches and cabling, and instead can use low-cost Ethernet - be it copper, fibre or wireless. iSCSI doesn't need any special iSCSI adapter cards or special cabling, it can use the existing NICs in the machine. Obviously gigabit ethernet is highly recommended =)

The disadvantages, however, are that you get slightly lower performance than Fibre Channel, as some of the network bandwidth is used up with the TCP/P packet headers, and it can use more CPU resources on your server as it has to calculate checksums for vast numbers of TCP/IP packets.

For, say, video storage where you need all the bandwidth you can get, iSCSI might not be the best option, yet for general file and print servers, iSCSI could be ideal.

If you're using iSCSI on other platforms (x86), it is possible to get dedicated iSCSI NICs that handle TCP/IP header and checksum creation in hardware, freeing up the host CPU for other more important tasks.

ATTO have a software iSCSI initiator that will talk iSCSI over a Macs inbuilt gigE port. Here's an excellent use for that second ethernet port on Xserves and G5s.

iSCSI RAID units are looking like they're also going to be cheaper than the equivalent Fibre Channel versions, however in some cases, a vendor's product range may have iSCSI at the low end and FC at the high end, with correspondingly more features.

Overland are selling some RAID units that may be an excellent alternative to Xserve RAID for smaller amounts of storage. These units go under the REO name and there are a number of units ranging from the 1RU, 2TB REO 1000 up to an expandable unit that can take 44TB, the REO 9000. The REO units, at the lower end, are iSCSI, and higher in the range they also have the option of Fibre Channel as an interface.