The Storage Champions: ATA/100 IDE RAID Controllers From AMI, HighPoint And Promise – THG.RU

The Storage Champions: IDE Hardware RAID Controllers

While both the processor and chipset companies viciously fight for market supremacy, other parts of the hardware sector inevitably move to the background. Intel’s Pentium 4 and AMD’s Athlon XP processor continue the struggle for the performance crown, and the chipset arena is as colorful as never before – by comparison, the situation amongst storage controllers receives little hype from the media and is often forgotten as a consequence. RAID (Redundant Array Of Independent Disk Drives) has become a powerful technology to speed up disk subsystem performance and/or to increase data safety.

The progress in developing IDE RAID controllers has generated powerful devices with a useful range of features. In addition, companies like AMI and Promise offer more sophisticated controllers that support even more drives (Promise FastTrak100 TX4, 4 IDE channels) or more complex RAID modes (RAID 5: Promise SuperTrak SX6000). IDE drives have always been more attractive if you consider price to be the most important factor. In addition, at the same rotation speed, they are not any slower than SCSI models in term of data transfer performance or access time. High-end IDE controllers might not be much cheaper than SCSI hardware, but the drives themselves usually cost only a third of the price! That’s why IDE RAID 3 and 5 is likely to replace SCSI RAID setups in systems that do not require 100% perfection, but merely 100% function.

In this respect, the three RAID chips from AMI, HighPoint and Promise can be seen as harbingers of the future of IDE – let’s learn a bit more about them now!

Available RAID Levels

First of all we should distinguish between “real” RAID modes and those you have to cut back for. Common RAID Levels are 0, 1, 0+1, 3 and 5. Only the latter two speed up performance while simultaneously enhancing data safety.

RAID 0

Many people do not consider Level 0 a real RAID mode, as it is risky in terms of data safety. RAID 0 does more than store data across two or more drives in so-called stripes (pretty much like a zipper). The idea behind this is to merge the capacity of all drives while increasing performance by distributing data over all drives, so that it can be read in parallel.

However, there is no fault-tolerance, as one defective drive will result in the complete loss of all data.

RAID 1

Mode 1 is the counterpart to Mode 0 and intended to increase data safety. Here, all data is simply mirrored to a second drive.

It is not faster than a single drive, but provides excellent data safety. Even if one drive crashes, the system will continue working.

RAID 0+1

This mode combines the two modes that I already described. First, take two drives and build a stripeset. This stripeset will be written simultaneously onto an additional array that will continue running if the primary one should fail.

RAID 3, 5

RAID Levels 3 and 5 are usually available with SCSI RAID adapters only. Starting at three drives, high-end RAID controllers use intelligent algorithms with checksums to distribute data on all drives that are available. RAID 3 uses one drive to store parity information, while RAID 5 stores that information alternating to all drives, offering even better performance. RAID Level 5 has become the dominant mode for critical servers. For more information on this topic please read RAID Overview at the IBM website. They have useful illustrations of RAID mode 5.

Data Safety vs. Performance

While RAID setups for servers are created to protect data against hardware failure, home users primarily focus on the possible performance gain. While a RAID 3 or RAID 5 setup provides excellent fault-tolerance together with pretty fast transfer rates and access, it is quite expensive to implement: first, you require at least three SCSI hard drives (usually, 5 or 6 are used). Second, these types of controllers are some the most expensive hardware you can buy.

The high price in itself explains why RAID modes 3 and 5 have not been accepted in the mass market. Home users usually won’t buy half a dozen hard drives and a $500 controller merely for the purpose of speeding up their disk subsystem. Instead, RAID 0 and 1 have become the popular modes that the majority of users implement.

As you will see later, using a four-drive instead of a two-drive stripeset does not increase transfer performance by much, but this makes sure that the minimum transfer speeds remain impressively high throughout the whole medium.

On-Board RAID vs. PCI Cards

There are several motherboards available that come with an additional IDE controller, usually an IDE RAID chip. Most of them are HighPoint chips, some are Promise chips and very few are AMI’s controllers (e.g. IWill). The main reason why such controllers are integrated directly onto motherboards? Price. On-board RAID gives motherboards an excellent added-value feature while not adding much to the overall board price tag.

PCI IDE RAID controllers start at approximately $60. Retail kits such as the ones we tested from AMI and Promise are more expensive, but they come with two 80-pin IDE cables, comprehensive manuals and sometimes additonal management software or other add-ons.

Software or Hardware RAID?

A few weeks ago, we touched upon the topic of software RAID, using the RAID capabilities of Microsoft Windows 2000 as an example. On the one hand, a software array is more flexible, as you can use almost every drive that is accessible by Windows. On the other hand rescuing the data can be more problematic if either Windows 2000 or one of the drives crashes – so the data safety issue is something that you should think about twice. Here’s the link to our Software RAID article:

RAID Without Additional Hardware: Do It Yourself With Windows 2000

AMI / LSI Logic MegaRAID IDE 100

On September 4, the controller division from American Megatrends, Inc. was sold to LSI Logic. Products and support are kept up without interruption. LSI Logic can be reached at http://www.megaraid.lsilogic.com.

The MegaRAID IDE 100 controller targets desktop computers, workstations and entry-level servers. As most IDE RAID controllers, it does not actually support RAID levels 3 and 5, which are considered the only true RAID modes. Instead, the MegaRAID supports striping (RAID 0), mirroring (RAID 1) or a combination of both (RAID 0+1).

The package includes a small manual, two 80-pin IDE cables and both a driver disk and utility CD. If you want to upgrade to Windows XP soon, you might be delighted to hear that Microsoft supports this controller by default.

Highpoint HPT370A

The HPT370 is one of the most popular IDE RAID controllers. It is widely used on higher-end motherboards from most manufacturers, as it is easy to integrate and can be used for RAID arrays and also as a standard ATA/100 IDE controller. While the system boots, the controller BIOS displays drive status information. Pressing CTRL+H, you will enter the setup menu, which is very clearly structured. Here you may setup a drive array: with two hard drives, you can chose betreen striping (RAID 0) and mirroring (RAID 1). Three hard drives can only be spanned or striped, while four can either be spanned, striped, or striped and mirrored (RAID 0+1). Choosing RAID 1 requires the drives to be synchronized, which took approximately 20 minutes with our 30 GB IBM DTLA drives.

Promise FastTrak100 TX2

Promise’s ATA/100 IDE RAID controller is available as a two-channel and four-channel version (TX2 and TX4 respectively). Striping several drives will easily exceed the maximum IDE data rate of 100 MB/s, which would make the 33 MHz PCI bus a serious bottleneck. Thus, the Promise controllers support 66 MHz operation in order to make use of a PCI bandwidth of 266 MB/s. Please be sure that the system will only run 66 MHz if all PCI cards comply to PCI 2.2!

The PDC2xxxx is not only available as a PCI card – sometimes it is also integrated onto motherboards (e.g. Gigabyte GA-7DXR), where it is called FastTrak Lite.

Test Setup

This time, the test setup does not correspond to our standard storage testing system (Celeron 500, i815 chipset). On the one hand, an Athlon 1200 is a more up to date configuration, and most of you expect results that reflect the real advantages you can get out of each RAID system. On the other hand, the Celeron 500 could have blurred possible differences between the three products.

Benchmark Results

Data Transfer Performance

As you can see, any setups using two striped drives results in pretty fast performance. Using two more drives does not speed up the maximum transfer rate by much, but it will raise the minimum rate – which is quite important for video editing tasks.

Business Disk WinMarks

Look at the results of four-drive setups with the Promise RAID controller! This one clearly outperforms the competitors, although it’s surprising to see the RAID 0+1 setup perform almost as good as the pure stripeset, which is in fact better than the two-drive RAID 0 setup.

Highend Disk WinMarks

Also in the Highend Disk WinBench test, the Promise controller achieves the best result. Yet the differences are not as large as one would expect in this particular benchmark, as the other system components play an important role as well (CPU, chipset, RAM).

Conclusion

In terms of data transfer speed, the differences between these three controllers are not that significant. It is more convenient to choose fast hard drives rather than to consider the many aspects of RAID controllers. However, this picture changes as soon as you take application performance into account. Here, Promises FastTrak100 TX2 is able to break away from the two competitors, as it performs superbly, even if you use RAID 0+1 setups (striping plus mirroring). In addition, the Promise manual is more comprehensive than the AMI manual.

Motherboards with an on-board HighPoint RAID controller usually don’t come with an extra manual that explains the controller features and configuration. In this respect, all three products are quite easy to handle, as they offer convenient BIOS versions to set up your desired RAID mode.

Following the recent acquisition of the AMI storage division by LSI Logic, we will have to wait and see how prices for the MegaRAID IDE 100 will develop. Currently, the FastTrak100 TX2 by Promise is the most expensive solution. HighPoint’s biggest advantage is that their products are widespread, thanks to the integration onto motherboards.

Given the choice of buying either a motherboard with integrated RAID or a simple model plus additional RAID controller, I’d definitely take the integrated solution. First of all, the performance difference is usually not noticable. Second, integrated solutions are cheaper, and third, you can still disable on-board devices and use something else (e.g. future ATA/133 RAID adapters).