Notes on the Accusys ACS 76130 (and 7630) RAID5 box

Introduction

The Accusys 76130 is SATA RAID5 solution. This is a real RAID5 (also does RAID0) solution, invisible to software. After installing three drives in the box, it acts as one drive, both electrically and to software, to the computer.

Accusys has discontinued the 7630 (three disk IDE RAID5) and the 7500 (two disk IDE RAID1) in favor of the newer SATA products. The 7630 and the 76130 are very similar in most regards, and this document will apply to both except where noted.

This box is very similar to the ACS75130/7500 system, however there are some differences, which are what will be covered here:

The center status light bar is now replaced with a third drive tray.
The trays look just like the ACS7500 trays from the outside, however they are not compatable -- different connector to the box.
On the ACS7630 (PATA), there are apparently two versions of the trays available -- a non-WD one (very much like the ACS7500) and an "all drive" version, where a short cable gives enough slack to mount any kind of drive in the tray. The one I have so far is the "all drive" version. The Accusys website is a little ambigious, apparently this version may be the only version available to buyers in the US. Or maybe only buyers in the US can get this version (in addition to the "non-Western Digital" version), the website wording is unclear. One "quirk" of this one is that the drives are not mountable to the tray with screws -- they just lay in position. This is probably ok for most applications, but I'm not sure I'd want to ship a machine this way. All things considered, I'd rather have the "anything but WD". I'm not fond of WD drives, anyway. (although, we did have three 40G WDs in-house which I used for testing)

Design and Operation Notes

The LED display of the ACS75170/ACS7500 is substantially reduced on the ACS76130, to make room for the third drive tray. Only LEDs on each drive tray will tell you how things are working at the moment. This display should be sufficient for most uses -- it is only a little disconcerting when rebuilding or intializing, and you don't know if it is almost done or many hours yet to go.
The ACS76(1)30 has a beeper which will help draw attention to it if it has a failed drive, is running in degraded mode, or rebuilding. This is different from the ACS7500, which rebuilds quietly. The thing is beeping next to me at the moment, and it is VERY annoying. It chirps every minute or so, which I think is excessive for a "everything is happening as it should be" alert. The beeper is penetrating -- it could be heard inside a data center with a number of computers and a ten ton Liebert air conditioner through closed doors.
Status of the ACS7630's ability to support "big drives" (>128G) is unclear. Early ACS7500 boxes had no provision for the new "Big Drives" extension to the IDE standard, the standard used on newer, larger than 137G IDE drives, later ones did support "Big Drives". There is no notification on the ACS7630s, and no new model number. I have tested and operated with an ACS7630 with three 250G drives, no problems have been noted, I think it is moderately safe to say "Big Drive Compatable", but I wish they said it... (ACS76130 is very clearly capable of at least three 500G SATA drives, and I don't see any indications of problems for bigger drives).
Rebuilding the array takes some time, but is much faster than the ACS7500, apparently. A set of three 40G drives took under half an hour to rebuild (I *think* fifteen minutes!), while the computer was doing a lot of disk writes.
There is monitoring software that comes with the ACS7630, unlike the older 7500s. This software can monitor either via the ATA interface, or via a serial cable, which is included with the SATA version. It seems the Accusys software can't talk to the SATA drive over the SATA channel, and they seem to know this, so they provide the cable.

ACS76130 vs. ACS75170

All things considered, I would much rather have the ACS75170. I'm biased towards mirroring and against RAID5, however there are places where sometimes storage density is more important than the simplicity of mirroring.

Mirrored drives can be extracted from the ACS75170 and used individually without the ACS75170 box, whereas a box failure on the 76130 would mean "no accessing your drives". So, you must have a spare box for anything resembling a critical system. Keep in mind, Accusys may not make this box forever, or future models may be incompatable with your current disk pack. A spare is not an option. That means the RAID5 solution is VERY expensive (though no more so than any other RAID5 solution -- they all suffer from this issue).
HOWEVER, the possibility of taking three 500G drives today and making a single 1T drive module in a single 5.25" FH bay on any computer is attractive for some applications...

Tests

proceedure:
install four "new" 40G IDE drives. Lock down one, power up machine. Power up other two drives, one at a time, wait for drive to spin up before powering up next.

Observation: ACS7630 takes about 15 minutes to initially build array on three 40G drives. During this time, it beeps about once every minute. Anoying. Array does not exist to computer, either. It also seems that it has killed the IDE bus on my computer, as the CDROM drive on a different channel seems to vanish to the BIOS until the rebuild is somplete. (should investigate if this is just a BIOS issue).

Proceedure: Power system down, exchange drives in two carriers, power back up.

Observation: This is a bad thing to do. RAID will not come up this way. However, swapping drives back to original position results in RAID coming up fine. Apparently, the distressed array controller does NOT write anything to disk under those circumstances.

Conclusion: Once mounted in the drive array box, the drives are "positional" -- you can not swap drives carelessly. In fact, you can't swap them at all. Moral: Label the drives when you install them, and certainly when you remove them for any reason. Make sure they are reinstalled to the same bay they started out on.

Proceedure: Build array. Power down, remove (and label!) drives. Replace with a new set of three drives, build array. Remove (and label) new drives, restore original drives back to their original position.

Observation: As long as drives were returned to their original bay, RAID sets could be swapped.

Conclusion: While it is possible to remove, replace, and restore a drive set in this way, it is dangerous. If one were to mess up the drive positions, getting the array back could be difficult.

Install 40G drives into ACS7630, and one-by-one, replace each drive with a 250G drive.

Observation: While drive is being removed and replaced, ACS7630 does not beep. Once the drive is locked down and the array is rebuilding, it beeps obnoxiously...Bah. When the swap was complete, I still had an 80G drive (to software), consisting of three 250G drives. Rebooting kept it still the same 80G size. I saw no obvious way to get the array "expanded" to the 500G potential size. Bummer, but not unexpected.

sidetracked proceedure: Remove six screws from bottom pannel of ACS7630. Stick small bit of tape over beeper which is visible.

observation: MUCH better.

Conclusion: not sure I would go into production this way, but for testing, it may save sanity of me and my co-workers. Note: if warranty is not an issue, remove four screws from back plastic cover (including one under the "dont open me" sticker). Otherwise, a car key to smooth the tape over the speaker did wonders.

Real world experience

My employer has a number of these devices in an application where the storage size of the RAID5 option was important. So far, we've had only one failure, but it was a doozy. The drive failed, placing a short across the power supply, shutting down the computer. This apparently also dammaged the Accusys box, as it was not able to access the new drive in the old bay. So, we moved this array to a new, spare box, as we had planned ahead for. This is where I discovered a "feature" I REALLY don't like about the 76130: it comes jumpered for RAID0, not RAID5. To its credit, it didn't just blindly distroy my data, it fought me hard, protesting strongly that it didn't like what it saw on the disks I had inserted into it. However, due to the impressive failure of the dead drive, I was ready to believe the entire array was dammaged, so I "forced" it, by turning on the system, mounting one drive, then the second, then the third (instead of having the two good ones in at power-on and "introducing" the third later). The 76130 gave in, and initialized the array to all zeros for me. It wasn't until I noticed that the resultant disk was 50% larger than expected that I realized I had probably toasted my array needlessly.

Moral: Set the jumpers on your ACS76130 how you want them to be WHEN YOU GET IT, even if it isn't being installed that moment.

Further update: After almost two years in operation, we've had a second drive failure in a 76130. This one went "as expected", no data loss, no downtime.

This machine is pretty impressive: four Accusys 76130s, at this point, each with three 500G drives for almost 4TB on-line, pluse a pair of 300G drives in an Accusys 75170 for the OS and scratch area. This system is an e-mail archive, it fills arrays, we take the full ones off and put them on the shelf, and repopulate the "emptied" RAID boxes with new drives. This ends up being a very nice solution -- we don't buy more than four or five months of storage in advance, so as time goes on, we benefit from bigger storage and cheaper drives.

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