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Cheap and Fast iSCSI Storage
At work we are nearly a 100% iSCSI shop. We completed the switch to iSCSI back in 2007 when we replaced our 2GB fiber channel solution with Equallogic. We were already using Cisco MDS9216i series fiber channel switches with IP services blades to provide hosts iSCSI access to the fiber storage, and we kept this around as a gateway to some legacy fiber channel equipment (a tape libary and an Apple Xserve RAID used as a disk-to-disk backup store).
Well, we finally outgrew the Xserve RAID and needed a new, low-cost storage array, with good sequential read and write performance, for our disk based backups. We wanted built in iSCSI, but I also considered just buying a external SAS shelf and using Linux as a NAS/iSCSI frontend especially when all the iSCSI options seems so expensive. After much looking around I came across the RS16-IP4 from Enhance Technology. I really didn't know anything about this company, but the unit offered native iSCSI with 4 1GB iSCSI ports, and the price was right at less than $5000. Also, you could bring-your-own-drives and the 1.5TB Seagate Barracuda drives were certified, so we picked up 16 of those. Now we have the box in, and have completed some initial testing with reasonable results.
Well, we finally outgrew the Xserve RAID and needed a new, low-cost storage array, with good sequential read and write performance, for our disk based backups. We wanted built in iSCSI, but I also considered just buying a external SAS shelf and using Linux as a NAS/iSCSI frontend especially when all the iSCSI options seems so expensive. After much looking around I came across the RS16-IP4 from Enhance Technology. I really didn't know anything about this company, but the unit offered native iSCSI with 4 1GB iSCSI ports, and the price was right at less than $5000. Also, you could bring-your-own-drives and the 1.5TB Seagate Barracuda drives were certified, so we picked up 16 of those. Now we have the box in, and have completed some initial testing with reasonable results.
Enhance offers several models of the RS16, including a JBOD options for a very low cost, and a dual port, 4GB fiber channel solution. We went with the RS16-IP4 since that gives of 4 1GB iSCSI connections that would work well with our existing iSCSI environment. We installed the 16 1.5TB Seagate Barracuda drives and power on the unit. The device pulled DHCP and we went to the web interface to setup the unit.
The web interface is simple, but sufficient. Via quick setup we selected our default RAID option (RAID 6). For more advanced setup you can carve the array up into multiple RAID types, or used striped RAID solutions like RAID10, 50, or 60. We were looking primarily for sequential performance (our backups are generally large file writes and reads) so we figured RAID 6 should offer sufficient performance with minimal risk of loosing the array due to a drive failure. The array can also be expanded by adding additional drive enclosures to the existing controller.
So now the big question, performance. Since we were looking primarily and sequential read and write we ran IOzone in throughput mode with 4 threads (matching the number of CPU's on the host). So far we've completed only minimal testing with a very non-optimized environment. The device is connected with only 2 1GB interfaces to a host with dual iSCSI HBA's (Qlogic 4062C). The network is non-optimal because the host system is connected into our iSCSI network (a stack of Cisco 3750's) while the storage array is connected into a blade in our core 6509 switch that's nearly 10 years old. That means iSCSI is having to travel through the 3750's, trunked via fiber to the 6509, to a first generation copper gigabit blade in a 6509 with SUP1's (let's party like it's 1999). Even with that handicap the device put's up decent numbers, although not stellar, around 150MB/sec for both read and write.
We're looking forward to setting up a more iSCSI friendly network (low latency, high speed) with all four links and seeing how far we can push it, but so far it looks promising.
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