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LSI Logic MegaRAID SAS 83o8ELP

From STORAGE Magazine Vol 6, Issue 6 - July/August 2006
 

Choices in the high-performance hard disk arena have been limited to parallel SCSI for far too long. Well the wait is over, as Serial Attached SCSI (SAS) is now proving to be one of the most exciting developments in disk interface technology. LSI Logic has been a pioneer in this field, as it delivered the first SAS controller card to market - and its latest family of SAS RAID cards brings a wealth of features to the table.

The benefits that SAS can bring to businesses are immediate. It supports both the SATA Tunneling Protocol and serial SCSI Protocol, which means SAS and SATA I/II drives can be linked to the same controller using exactly the same connector plugs. There's much, much more, as SAS and SATA drives can be mixed on the same backplane and hot-swapped, and the serial point-to-point interface provides a full duplex 3Gb/sec link to each hard disk. The connectors also have another benefit, as they are small enough to be used on 2.5in. hard disks, and this is already having a major impact on rack server design.

We've been watching the steady migration in rack servers from parallel SCSI to SAS and the 8308ELP on review directly targets this market sector. It's a low-profile card that's specifically designed to fit in rack chasses from 1U upwards and comes with a pair of onboard four-port connectors.

The card ships with two four-port expander cables, each with integral power cables allowing up to eight hard disks to be linked directly to the card. The card sports a 500MHz Intel IOP333 processor, plus 128MB of embedded cache memory, and it'll also accept an intelligent battery backup pack, which costs around £84.
Installation is simple enough, as the card and arrays can be configured using the card's own WebBIOS startup menu or the new Storage Manager Windows utility. The latter is a huge improvement on its predecessor, which has been criticised for being unwieldy and limited in features. The new utility is far slicker and provides easy access to views of logical and physical drives, arrays and status information. It also offers an automated array configuration wizard, which will pick the best array type for the number of drives attached.

The 8308ELP was installed in a 2.8GHz Pentium D Dell server, equipped with 1GB of memory and running Windows Server 2003. A quad of Seagate Cheetah 15K.4 SAS drives were connected to one interface and configured from the Storage Manager as individual drives. For performance testing we used the open-source Iometer utility configured with one disk worker, 256KB transfer requests and 100% sequential reads.

Starting with one worker assigned to the first drive, we saw Iometer report a speedy 87MB/sec. We then assigned a new worker to each drive and watched this rise to a cumulative 174MB/sec for two drives, 262MB/sec for three drives and 351MB/sec with four drives.

For comparison and compatibility tests, we replaced the Seagate drives with a quartet of Western Digital Caviar SATA/3Gbps drives. Running the same Iometer tests saw a very similar set of performance figures, which peaked at a cumulative 353MB/sec with all four drives in the mix. Having run similar tests in the lab, using four Seagate Cheetah Ultra320 SCSI hard disks, we know that standard 320MB/sec SCSI runs out of steam at around 275MB/sec with four 15K drives attached to one channel.

The new SAS 8308ELP impresses by delivering a fine range of features at an affordable price. Performance is particularly good and remote management facilities see great improvements, making this a top choice for SAS deployments in rack servers where fault tolerance is a high priority. ST

Product: SAS 8308ELP
Supplier: LSI Logic
Tel: 01344 413115
Web site: www.lsilogic.com
Price: £432