Despite offering lower prices for network storage the latest iSCSI appliances can’t compete with fibre channel SANs in the performance stakes. It may be more cost-effective to install but we saw the limited speeds of the REO RA2000
from Overland Storage which also failed to deliver any serious fault tolerance.
As an example, consider Chapparal's RIo eXP. The price tag may be higher but the product looks to have it all as it combines masses of redundant components, a huge storage capacity and extreme network performance over 2Gbit/s fibre channel. There’s much more as it even allows you to combine Serial ATA and fibre channel hard disks on the same controller allowing companies to select a mixture of performance, capacity and cost.
Fifteen storage enclosures can be linked to one controller unit allowing you to expand to no less than 240 spindles. For fibre channel this is currently a maximum capacity of 35TB whilst SATA takes this up to an amazing 60TB. The 1U controller unit delivers a pair of RAID controllers called Data Managers and each is endowed with an 850MHz Intel Mobile Pentium III processor, 512MB of PC2100 SDRAM and a battery backup. A serial port on each module provides local access to an extremely well designed CLI while a 10/100BaseTX Ethernet port offers management access to an equally impressive browser interface.
Two 150W supplies look after power, up to four Data Gates each provide four 2Gbit/ss fibre channel SFP ports and every module is hot-swappable. The ports on each Data Gate are separated into pairs where one links to the disk enclosures and the other is for host connections. Two ports can be hubbed together into a single loop allowing all LUNs to be seen by both Data Managers. With this feature switched off each Data Manager only reveals its own LUNs so you can configure the system for a switched SAN or for direct-attached host systems.
The 3U drive enclosures sport a pair of 450W hot-swap supplies and two, four-port fibre channel SFP modules. Sixteen drives can be fitted in each one and the review unit came supplied with 36GB Seagate fibre channel drives. Installation is reasonably straightforward and the browser management interface is extremely easy to use.
Plenty of status information is provided on every component. You can keep an eye on environmental values, including temperatures, in every module in each controller and warnings can be used to generate email alerts. It’s a cinch to create just about any type of RAID array you want and you can mix and match different types. On completion each is assigned to one Data Manager automatically or you can manually select one. If this module fails, the arrays automatically becomes the property of the other controller until the faulty unit is replaced.
For performance testing we used a QLogic SAN Connectivity Kit
and configured the Data Manager ports for a direct attached host environment. We connected a Windows Server 2003 system to each Data Manager and saw the two RAID-5 arrays we had created from the browser interface appear simply as two very large (and extremely fast) local drives.
Running the open source Iometer with 64KB read transfer requests and ten outstanding I/Os we can report transfer rates of 193MB/s and 195MB/s srespectively, which is near enough to wire-speed for 2Gbit/s fibre channel. Adding another direct attached server to each Data Manager saw these figures gradually settle down to an average of around 95MB/s for each host confirming our original findings.
The RIO supports up to four 2Gbit/s fibre channel loops so to test maximum performance we unhubbed the Data Managers and created four RAID-0 striped arrays comprising two disks each. Iometer was run again with one disk worker on each server assigned to a different array and each disk worker returned average transfer rates of no less than 191MB/s for stunning total throughput of 764MB/s.
It may be more costly to implement but fibre channel is clearly the storage infrastructure of choice for outstanding performance. The RIO eXP certainly delivers in this department but also provides exceptional fault tolerance and a total storage capacity that’ll satisfy even the largest enterprise.
The choices are simple – if you want top performance, the highest storage capacities and are prepared to pay a premium, then fibre channel is the only storage option. iSCSI is much easier to implement as it can use existing Ethernet network infrastructures but the RIO eXP blows everything away for speed, storage potential and redundancy.