REVIEWS

RAID Gets High Grades For Capacity And Performance

by Eric Carr

If the sheer number of vendors is any indication, RAID (especially the platform-independent, SCSI-to-SCSI RAID) is the business to be in these days. We evaluated 17 products (10 here, seven others in our October 1 issue) with an emphasis on availability, capacity and performance. We weren't disappointed, and we don't think you'll be either. All the arrays

have a unique set of features to help them keep going under the worst conditions. Each array can easily hold 20 to 40 GB of data, which is plenty for most environments and applications. Due largely to increases in media performance and corresponding cost reductions, these units all perform well at a significantly lower cost per unit of storage than the arrays we tested last year.

The LAND-5 DS200 epitomizes state-of-the-art SCSI-to-SCSI RAID, taking the top honors in this evaluation (see the October 1 issue for that review). This product is well executed and a good value to boot. The DS200 has a number of optional remote management features that will make you drool, or at least, make your eyes glaze over.

While LAND-5 focuses on management, the folks at CLARiiON must have read our last review and heeded our comments. The hot new C-150 sports almost all the features of the venerable C1100, but at a far more realistic (and easily justifiable) price. All the while, CLARiiON continues to excel at form, fit and finish--a lead we'd like to see more vendors follow. If you're budget conscious, try Polywell's SUMA RAID. The name's unusual, and th e quality could use some improvement, but the product is a great value.

Our evaluation criteria favor large, industrial-strength arrays. As such, modular and desktop units don't do as well as the larger monolithic models. That's not to say they're bad by any stretch. Products from Storage Solutions, Cranel, Artecon and Micropolis provide very scalable and affordable solutions. You can acquire one of these units largely unpopulated for a reasonable price and build from there. However, the modular nature imposes certain redundancy limitations. You'll need to decide whether you can live with those penalties.

Data General CLARiiON Model 150 Disk Array

The CLARiiON business unit of Data General has pulled off a minor miracle here: It has retained the best features of the C1100 series array (a Network Computing 1995 Well-Connected Award winner) and repackaged it as the far more affordable C150. Like its larger brother, the C150 is built with availability in mind. A multiplicity of RAID levels coupled with everything but redundant line cords and controllers make this system as fault-tolerant as possible, among the products we tested. Other vendors should take note of Data General's attention to detail. For example, when we removed a quick-release fan, simulating a cooling failure, the other fans in the unit increased speed to compensate. We didn't see that level of functional thinking in any other unit.

The C150 is designed for end users. As with other CLARiiON products, documentation was exhaustive and focused on integrating the product into a variety of environments.

While competitive with LAND-5's DS200 in availability and performance, the C150 is clearly designed to be deployed in a secure environment, such as a data center. There's a distinct lack of status LEDs, making it hard to see what, if anything, is wrong with the unit. There's no security for the drives, power supplies, fans or controllers, and no audible alarm. Every other unit we tested could beep, scream or chirp to warn us about a problem.

Polywell SUMA RAID

We could characterize the SUMA RAID array best as a unit with a plethora of features at a bargain price. Indeed, no other unit could match the feature set of the SUMA RAID at less than $1 per megabyte. Only the MicroNet RAIDbank and the LAND-5 DS200 had equivalent features at lower dollars-per-megabyte storage costs, but they had significantly higher overall prices because of the larger 4-GB drives they use.

While the Polywell unit compares favorably with the six other Mylex 960-based products we tested in availability, the enclosure does not have any environmental monitoring features to warn of temperature problems. If you don't know about a problem, you can't take preventive measures. We'd like to see Polywell focus more on quality, too. The unit delivered to us initially had a rough ride from south San Francisco, just 10 miles from our lab. The packing container wasn't up to the job of protecting the unit, and drives arrived in various unnatural orientations in the disk cage. Talk about vendor responsiveness--the unit was repaired in a little more than a day.

Storage Dimensions SuperFlex 4000

The rack-mount SuperFlex 4000 is also among our top contenders and is comparable to the MicroNet RAIDbank but for different reasons. While the RAIDbank is less expensive on a dollars-per-megabyte basis, the SuperFlex has dual line inputs and quick-release power supplies--features that contribute to its enhanced availability: If power goes on one line, the other can keep the array going. If there's a problem with the power supply, it can be hot swapped in seconds without tools. These are important features when the array has to be up constantly.

Just like last time, though, we found that the disk carriers have enough clearance in the drive bays to allow for some movement. We couldn't disconnect them by wiggling, but we would like to see Storage Dimensions work on this situation.

Optima HST 10000

While some other vendors can equip the array wi th a tape drive, the HST 10000 was the one array that came with an integrated DAT drive. This brings up a point: With all this redundant capacity, you should be doing some sort of backup of the data to another medium. These arrays, while fault-tolerant, cannot protect you against natural disasters. If your data is important to you, back it up.

The HST is very similar to the Legacy SmartArray XE. However, the XE has greater capacity and a more intelligent enclosure, monitoring temperature and displaying a problem in plain English. These are both features the HST can't quite match.

The HST is somewhat more expensive than other units with similar components. For example, the SUMA RAID, RAIDbank and DS200 all come in at just less than $1 per megabyte while the HST is up with the SmartArray at about $1.50 per megabyte. If you take out the tape drive, the price drops into the $1.25 to $1.30 range.

Raidtec FlexArray FX

The Raidtec FlexArray had the distinction of having the lowest price per unit storage (just 76 cents) of any array we tested, even beating out the MicroNet RAIDbank by a few pennies per megabyte. Even so, for large capacity installations, you may want to look elsewhere, since the FlexArray can use only a maximum of five devices in its cube-shaped enclosure. The sixth drive bay is for a spare drive, and is not connected to the controller. Look elsewhere, too, if you want to have different RAID levels operating simultaneously. Here you get one level for all devices.

Features contributing to general array availability, or fault-tolerance, are on par with those from Optima, Legacy, Winchester Systems and AIWA/Core. Unlike the CLARiiON unit, you can deploy the FlexArray anywhere, because its locking drive shuttles and quick-release power supplies are both secured by the locking steel doors on the front of the unit.

We liked the FlexArray's "Recreate Drive" button that can be used to replace a dead drive on the array quickly. You just replace the dead drive, let it spin up and press t he button. It's operating system independent. There's no need to attach a terminal to the unit or go through a bunch of menus to select the function. No other unit had this "one button" functionality, and we think it's a good idea. When the array is down, you want to get it back on-line as quickly as possible.

ITC Ultimate-1/FX

The biggest surprise with ITC's Ultimate-1/FX was that just a single RAID level was available to drives in the array--RAID 1. No other product offered a single RAID level. This severely limits the choices of protection. You can argue that as disk prices drop, RAID 5 (and the attendant write penalty) becomes less of an issue, but we like having a choice. This lack of RAID levels, coupled with a lack of environmental monitoring and an inability to hot swap the fans has a negative impact on the ITC unit's availability. The unit was very fast, however, and capacity with the 4.3-GB disk drives wasn't an issue.

Certainly the economics of the unit are compelling: The Ultimate-1/FX was the second most cost-effective unit. Although eight devices can reside in the enclosure, ITC only offers two drive capacities. Finally, configuration is difficult via the two-button LCD, and choices (with mirroring being the only option) are limited.

AIWA/COREarray 20000

Lackluster performance and an inability to hot swap fans sent the AIWA/COREarray 20000 way down the list. Like the Cranel unit, RAID level 1 isn't an option; only RAID 3 and RAID 5. As a result, availability suffers. Capacity, however, is not an issue, with a variety of drive sizes available and six device bays, much like Andataco's RAID Lite.

The 20000 is engineered well and much like the CLARiiON C150, there's plenty of detail in the product. For example, the drive LED diagnostics are excellent, and we particularly liked the system log that showed all the activities the array had undergone. You must use a terminal to configure the 20000, via the supplied DOS and Windows communication programs. The Windows progra m

delivers much more information about the array than you can get from looking at the terminal, including real-time status graphs and some history as well.

Unfortunately, the array exhibited less-than-stellar performance numbers for the configuration we were using, and we could only test the RAID 5 configuration. We noticed that the default block size for the unit was 64 KB, and perhaps the unit would have done better with that setting. However, we were testing other devices with an 8-KB block size, and we wanted to be consistent across platforms.

ANDATACO RAID Lite

The RAID Lite product includes many of the components the LAND-5 DS200 and Storage Dimensions SuperFlex 4000 have. Unfortunately, the product gets torpedoed by an enclosure that doesn't have hot swap fans and can't warn you that temperature inside the array has reached a critical state. In addition, the unit is expensive, at more than $1 more per megabyte than the value-leading Raidtec and ITC units.

Granted, each disk module has fans to go along with the several larger fans in the enclosure, so if one fails, you probably wouldn't be affected. However, you wouldn't know of the failure, either.

As the "Lite" moniker implies, this array is more suited to the desktop, or perhaps deskside. The enclosure doesn't have the device capacity of the larger products like the Smart-Array, although ANDATACO offers a wide variety of drive capacities from which to choose. Scalability, therefore, while not great, is solid. On the upside, the name does not apply to the unit's performance. We observed some of the highest throughputs at RAID 1 of any array we tested.

Micropolis RAIDION LTX 6.3

Micropolis has built an enviable business based on the concept of modular, stackable RAID products. Indeed, you can go from three to 28 drives in the array, just by adding drives and three expansion chassis assemblies. This is a great idea! You can start small and affordable, and grow when you need to.

However, array redundancy is neces sarily limited by the modular approach. If a power supply (one for each drive) goes, the drive stops and the array goes into a critical state. The same scenario applies to the fans that ventilate each drive. There's no fall back position. There are no components to share the load.

Since this is also the only array made by a drive vendor, you're committed to using Micropolis drives in the product. Others use drives from a variety of sources.

The RAIDION LTX sports an impressive setup facility--by either terminal or the retractable LCD panel in the base of the unit. Certainly the LTX was one of the easiest arrays to configure. While it's performance was much better than the Clovis and AIWA/Core products, it was a little below the others.

Clovis MultiStor-R

The MultiStor-R tends to suffer in the crucial area of availability: It doesn't have redundant fans, nor are the fans hot-swappable. Cooling is critical in an array, and although the MultiStor-R monitors internal array temperature, this lack of redundancy is a glaring oversight for this kind of product. You'll need to bring the array down if a fan fails. Also, Clovis only offers RAID levels 3 and 5, further limiting availability.

MultiStor-R's performance was better than that of the AIWA/Core unit, but still well below the other products. Scalability and capacity are good, with plenty of space and a number of drive capacities offered. We also like the array on rollers and the lockable mesh door to secure the individually lockable drive carriers further. The controller can support multiple hosts coming into the array linked to different logical drives, which is great for supporting multiple platforms with consolidated storage.

However, the pricing on the MultiStor-R needs some attention, having the dubious honor of being the most expensive array on a cost-per-unit storage basis. There are plenty of other solutions here that provide the same level of security, capacity and availability for a fraction of the cost.

Eric Carr owns F1, an independent consulting agency in Mountain View, Calif. He can be reached at 73770,2235@compuserve.com.

SCSI-To-SCSI RAID: How We Tested

We evaluated the performance characteristics of each array with the help of the RAID Advisory Board (RAB) and Peer Protocols, a SCSI testing agency (and RAB member) in Newport Beach, Calif. Peer has written a test suite that conforms to the recently released RAB Disk Array Test Specification.

The part of the test suite we used presents a comprehensive set of test "workloads" to the array while measuring input/output performance and throughput. For a full description of our testing procedure, see our October 1 review, page 122.

October 15, 1995