As far asyour server knows, the JetStor II-LVD RAID from Advanced Computer &
Network Corp. (www.acnc.com) is just a big hard
drive. This is one of the advantages of external RAID
systems. You don't need any special software to set the system up or control it. This lets you
connect the JetStor to any computer hardware running under any operating system.
JetStor II-LVD RAID
Advanced Computer & Network Corp.
Pittsburgh, PA, 412-683-9010 Description: External RAID Subsystem with dual RAID Controllers Cache: 32 Mbytes (mirrored) Interface to host: 2 X Ultra2-LVD SCSI Interface to drives: 2 X Ultra2-LVD SCSI Enclosure Drive bays: 8 half-height dual internal Ultra2 SCSI buses, SCA connectors, dual power supplies (hot swappable), dual cooling systems (hot swappable) Performance ·Cache test: 181 commands per second, 45.5 Mbytes/sec. ·Transaction rate: ~300 I/Os per sec. ·Throughput: ~50 Mbytes/sec. Advantages: Terminal based set-up software is platform independent. High transaction rates and high throughput. Disadvantages: Set-up software is not user friendly. Manual is fit for RAID experts only. Price: $9,900
The JetStor II is a desktop RAID array with eight drive bays and dual redundant power supplies and
cooling systems. All redundant components including the power supplies, cooling fan modules, and
drives are hot swappable, that is, they can be removed and replaced while the system is operating. It
is a compact unit. At 19 x 9 x 12 inches, it is about the size of a desktop PC. Its small size and
built-in cooling mean that it can be installed in any computing environment.
Operating system neutrality extends to the JetStor's set up process, and connecting to your
server is relatively simple. The setup is handled via a four-button front control panel or via
terminal software on a computer connected through its serial port. The control panel route is possible
for the patient, but the terminal software is much easier to use. The computer you use doesn't
even have to be the computer accessing the RAID volumes. System administrators can connect multiple
JetStors to servers and configure them with a laptop computer.
The JetStor II is currently equipped with RS-232 serial ports only, but the company plans to offer
universal serial bus and Ethernet ports by the second quarter. Ethernet ports should support remote
and administration via a browser interface.
The JetStor has two SCSI channels to the host and two channels to the drives. Each channel supports
four Ultra2 SCSI drives. The host RAID connectors can both be connected to one host computer or they
can be connected to two separate hosts. The drives can be set up in as many as four separate RAID
arrays. RAID levels 0, 0+1, 3 and 5 are supported.
The JetStor also lets you create separate
partitions within each array (an array always has to have at least one partition). The built-in set-up
software lets you assign each of the partitions to either or both of the external SCSI channels. You
have to be careful not to connect the same partition to more than one server or to two controllers on
a single server. This is important because if you have two queues of commands accessing a single
volume simultaneously you will get some serious errors.
Any drives that are not configured in the
RAID are automatically set up as spare drives. The system can be set to alert an administrator of
problems via fax or pager, and it will automatically rebuild the array when a replacement drive is
added. Additional drives can be added to an array on the fly without taking the system down (though
you should back it up before you do any RAID array management).
Our test bed was a 600 Mhz Pentium
III computer running Windows NT 4.0 (Service pack 4) with an Adaptec Ultra2-LVD SCSI host adapter. We
configured the JetStor II with a single six-drive RAID 5 array and one spare drive. The array was
fitted with the OEM version of IBM's 18-gigabyte Ultrastor drives.
In our initial tests, which
measured the speed of the controller's cache and the interface, the JetStor II reached
transaction rates of 181 commands per second and transfer rates of 45.5 Mbytes/sec. This compared
favorably with earlier tests made on a single 9 GB drive (12 Mbytes/sec.) and a RAID array built
around an internal controller (35 Mbytes/sec.).
In a second round of more rigorous testing,
performance was even better. Throughput rates reached 50 Mbytes/sec. using 2 Mbyte transfer requests
to simulate large, sequential file access. Input/output rates hit 300 per second with 2 kilobyte
transfer requests used to simulate database operations. With file size set at 10 kilobytes (the
typical size of a compressed document image), transaction rates were about 123 I/Os per second.
Two things were notable about the hardware itself. The JetStor II houses the control panel and master
switch behind a lockable door, and you use the same key to control the master switch. This double
security will prevent an accidental shut down. Less reassuring were the power supply connectors, which
didn't fit tightly and came loose when we moved the unit. A simple fix would be a pair of clips
holding the power cables in place.
Considering its high throughput and transaction rates, the JetStor II is a good general-purpose array
for both database access and document file storage. If you have a small network and can only justify a
single RAID system, the JetStor II would be a good choice.
