Controller Ratchets Up Raid Performance

3ware Inc.s Escalade 8500 Serial ATA RAID controller takes an evolutionary step up from current Ultra ATA offerings and offers a price advantage over SCSI disk systems.

Serial ATA provides more features and better performance by design than Parallel ATA and offers an attractive storage alternative for users and system vendors alike. IT managers should consider 3wares Escalade Serial ATA controllers to provide robust, inexpensive storage for workstations and midrange servers.

Serial ATA provides better connectivity by using a point-to-point signaling technology. Each storage device connected to the controller has a dedicated bus with full data bandwidth, up to the current specification maximum of 150MB per second. The cables used to connect Serial ATA devices to the controller are also longer and thinner than Parallel ATA cables, thus allowing bigger systems to handle more devices while providing better air flow that enables vendors to build more compact systems.

Parallel ATA, on the other hand, uses a master/slave shared-bus architecture and requires bulky cabling that can be inefficient in larger storage systems with multiple devices.

SCSI is still the more dependable storage system, with better mean time between failures, because the higher-priced SCSI drives are designed to last longer than ATA offerings. However, Serial ATA is catching up as drive makers improve manufacturing processes. And with lower prices than SCSI systems, Serial ATA storage is a viable alternative for SCSI in non-mission-critical applications.

Serial ATA also supports hot-swapping and hot-spare drives, a must for enterprise-level applications.

Serial ATAs first phase was announced in August by the Serial ATA Working Group, and the planned 10-year road map will bring Serial ATAs data transfer rates to 300MB per second in the next few years and 600MB per second at a later date.

Serial ATA RAID controllers are targeted to provide robust, inexpensive storage in workstations, servers and enterprise data applications. 3ware is not alone in the market: Adaptec Inc., LSI Logic Corp. and Promise Technology Inc. are also expected to launch Serial ATA RAID controllers this quarter.

The 3ware Escalade 8500 Serial ATA RAID controller supports RAID levels 0, 1, 5 and 10 and unconfigured JBOD (just a bunch of disks) arrays. We tested the $599 eight-port Escalade 8500-8, which can support eight Serial or Parallel ATA drives. Prices range from $449 to $849 for the series, which can support four to 12 drives. The Escalade 8500 controllers support Linux as well as the Windows 98, Millennium Edition, NT, 2000 and XP operating systems.

We installed the 8500-8 in a white-box test system with Intel Corp. dual 866MHz Pentium III processors, 1GB of synchronous dynamic RAM and four Maxtor Corp. DiamondMax Serial ATA hard drives. Two drives had 80GB of capacity, and the other two had 120GB. The card was easy to install, and the Serial ATA cabling made putting the drives together much less cumbersome than building a standard ATA drive configuration.

We set up a RAID 5 disk array with four drives and installed Windows 2000 Server with Service Pack 2 on the test system. Using Intels Iometer testing tool, which benchmarks file transfer performance, the Escalade 8500-8 clocked more than 110MB per second in sequential reads and more than 12,000 I/O per second.

The Escalade 8500 comes with useful management features. We first configured our test disk array using the 3ware BIOS tool, which allowed us to create, maintain or rebuild disk arrays by adding or deleting disk members.

The 8500 controller series also comes with 3DM (3ware Disk Manager), a Web browser-based utility that allowed us to monitor and manage the array and its disks locally or remotely. The 3DM utility is useful for remotely configuring the controller and also allowed us to download the error logs.

We were disappointed, however, that the 8500-8 has only 2MB of on-board memory cache without the ability for expansion and also lacks battery backup for data recovery during power failures. Expandable memory caches are a regular feature in SCSI RAID controllers; nevertheless, the Escalade 8500-8 still provided a lower cost for the performance we logged during tests.

Technical Analyst Francis Chu can be reached at francis_chu@ziffdavis.com.