LSI Logic SAS3442X review

LSI Logic is making a habit of beating the competition to the punch. The MegaRAID SATA 300-8X allowed it to deliver the first SATA II RAID controller to market, and with the SAS3442X we bring you an exclusive look at the very first SAS (serial attached SCSI) controller card.

We've had to put up with parallel SCSI for nearly 20 years now, so the benefits of SAS to business storage applications are immediate. Along with a serial point-to-point interface, it supports the SATA Tunneling Protocol and the serial SCSI Protocol, meaning SAS and SATA drives can be linked to the same controller using exactly the same connector plugs. You get a full duplex 3Gb/sec link to each hard disk, while support for the Serial Management Protocol allows up to 128 devices to be connected using SAS expanders. There's much more, as both SAS and SATA drives can be mixed on the same backplane and hot-swapped. The smaller connectors will eventually also allow 2.5in drives to be used, plus the thinner cables will improve airflow.

The SAS3442X is an eight-port host bus adaptor (HBA) and provides one internal four-port connector and one four-port socket on its backplate. The latter allows external hard disk arrays to be linked to the same card using InfiniBand 4x connectors and cables. The card is supplied with an internal interface cable that provides connections to four SAS or SATA hard disks and it also offers basic mirroring for two disks with hot-standby or striping as well. For performance testing, we used a dual 3.2GHz NEC Express5800 server running Windows Server 2003. We installed the card in a 133MHz PCI-X slot and our thanks go to Seagate and Fujitsu for providing us with some of the first samples of their respective 15K.4 Cheetah and MAU3147RC SAS drives.

We started with a single drive and ran the open-source Iometer against it configured with one disk worker, 64KB transfer requests and 100 per cent sequential reads. We then added a second, third and fourth drive, each time using the same Iometer parameters but with an extra worker assigned to each drive. For comparison purposes, we replaced the card with an Adaptec Ultra320 SCSI HBA and ran the same four tests using Seagate 15K.4 Cheetah Ultra320 SCSI hard disks.

Results from the first three tests showed there's little between the two technologies. The SAS tests returned 88MB/sec, 177MB/sec and 265MB/sec, while Ultra320 SCSI delivered 90MB/sec, 179MB/sec and 265MB/sec. However, with the fourth drive in the equation, the single SCSI channel showed signs of running out of steam as four Iometer workers reported a small increase to 275MB/sec. Performance for four SAS drives continued unabated with Iometer showing a top throughput of 353MB/sec for both Fujitsu and Seagate. We also checked compatibility claims and successfully mixed Seagate SAS and Western Digital Raptor SATA hard disks on the same card without any problems. Performance wasn't as good as SAS, but the four Raptors did deliver a total cumulative throughput of 272MB/sec.

SAS is without doubt one of the most exciting developments in enterprise hard disk interface technology. Its potential for businesses across a wide range of storage applications is unquestionable and, once again, LSI Logic will prove a very hard act to follow as the SAS3442X delivers on all counts.

Author: Dave Mitchell