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raid 5 (6 disk array) power requirements.

  • Power Supplies
  • NAS / RAID
  • Components
Last response: in Components
January 31, 2007 8:04:05 PM

i have been asked to fix a faulty web server with the following specs:

Promise Supertrak sx6000 RAID controller (pci)
6 ide hard drive array (controlled by the above pci card)
1 solo ide hard drive
intel celeron 700 mhz (p3 socket 370)
512 mb ram (spread over 4 dimm slots) --> (as this is an older machine)
van 460-n power supply (by Vantec)

os: windows xp pro.

Although this setup has been working in the past, I have been experiencing a few problems which I beleive are due to a lack of power, but due to my limited experience with raid 5 disk arrays, I would appreciate any second opinions.

First the dvd burner stopped functioning properly. Although it was being identified by windows, I could not read simple data cd's. I replaced the drive with an older cd/r drive, re-booted my computer normally and was able to read the cd with no problems.

I then restarted the computer with the intent of loading a boot cd, and encountered an error with my raid controller. Drives 3, 4, 5, and 6 of my disk array were being identified as either damaged or disconnected, and my raid controller was now offline due to the "failed" drives. (The controller will only go into an offline mode if 2 or more disks are disconnected or damaged).

I checked all the connections. I removed each drive seperatly from the array and tested them --> Each one was identified by windows and could be seen in the disk managment utility. But still I am now unable to initialize the disk array. If I continue and log into windows without initializing the raid 5 array, windows identifies the raid controller as new hardware, and prompts me to install it.

I feel this is an issue of insufficient power, but if anybody can confirm this, or offer any sort of advice that would be much appreciated.

thanks a lot,


More about : raid disk array power requirements

January 31, 2007 8:28:12 PM

460 watt PSU I presume?

FYI, ran a similar RAID5 (**edit** with 6 IDE drives) setup on a 380w PSU with an overclocked 3.2GHz Pentium 805 (probably pulling 100w+) and a separate videocard (X300 based) with no problems at all.

Having said that PSUs may lose efficiency/capacity as they get older (someone please correct me if this is nonsense) ... do you have a second machine you can put alongside and power the HDDs from to take the load off that one?

Alternatively, you might try transferring the RAID card and the drives to another machine - the card should remember the array setup so you should keep all the data okay.

Good luck,
January 31, 2007 8:30:21 PM

It looks like you need a much larger PSU.
Such as SeaSonic 650 or OCZ 650.
The big PSUs usually have 6 SATA and 6 Molex connections.
But you said you have IDE drives.
So, you may also need some SATA to Molex adapters.
A problem is these large PSUs are also made to handle large video cards (with the PCI-E connections). So you will have some unused 12v power.
Related resources
January 31, 2007 8:59:45 PM

Your symptoms are indications of a failing PS. I've seen this on other deciated NAS boxes. When the PS is failing it generates random errors.

Capacity should be fine though, provide you are not running huge drives.
February 1, 2007 4:08:58 AM

Each additional HDD ads about 1.5A to 2A to the system's power needs on the +12v rail(s).

Please breakdown what computer parts go to which rail. What do the 3.3v, 5v, etc connect to? Why is more than one rail needed? (I understand about max amps)
I did read your 101 sticky. I want to understand this because I am using 6 HDDs, 2 DVD Roms, many fans & lights.
February 1, 2007 5:28:11 AM

Well all the items you just listed use the +12v rails. If you check at the bottom of PSU 101 you will se a bunch of links. The last link there Gives a nice breakdown of the PSU connectors and exsplains what the diffrent voltages are for. Not the +3.3V was added to power the chips on the motherboard such as the chipset and bios. But i'll let you read it there for yourself.

Here is that link.

This is enough reading material to keep me happy for a while. Thanks!
February 1, 2007 12:44:22 PM

If your Supertrak supports (and is using) staggered spinup for the drives, it greatly reduces the initial current requirement from the PSU.

If it didn't, you'd factor for about 2A per drive, but the larger the # of drives the more this generalization becomes inappropriate, because momentary peak at the instant of power on is actually well above 2A per but quickly falls, so the timing of the voltage rise is as important as capacity. This is best seen in retrospect, nobody that I'm aware of is testing this kind of momentary surge capability vs duration of voltage depression on PC PSU.

I can tell you that I've ran similarly equipped systems for years from decent 300W PSU with about 12-14A @ 12V ratings. Your 12V rating need not be particularly high since the Celeron/P3 era boards uses 5V, 3.3V instead of 12V for CPu and video supply step-down circuits.

If your 460W(?) PSU is working properly, you have no chance at all of having insufficient power, but that doesn't rule out a PSU failing, among other possibilities like bad cabling or a power surge.

When you write that you removed each and tested them, what is that supposed to mean? You can't just individually hook up one drive from a RAID5 and expect Windows to help, it would be better to never ever ever do that, windows likes to write to drives if you're not careful what you do.

Once the controller has the drives attached and configured as an array, these parts should stay together. Always. You move the whole thing to a different system or don't, but not individual drives. This is unless you are sure you have a complete, tested working backup of that data, if you do then it's a different story but no mention of this was made so I err on the side of caution since it's not just one drive *missing* but several.

What should've been done is to take the controller and drives and try them in a different system. It may be easier if you can put the other system next to it and leave the drives fastened in the orig. system, just powered by the other one with the cable running to them, if not in easily swapped trays.

I suggest that you isolate things more. Leave the raid controller and drive disconnected and see if the system is otherwise stable. Take voltage readings with a multimeter.

If the raid controller doesn't recognize all array members, there is no point in booting Windows. Just stop and work outside of windows. After hooking up the controller and drives in another system, if they're not working still but the controller still seems operational (for example you might try setting up a test array with two other drives, not the ones in question here) at that point it depends on what this data is worth, if it's time to send them to a recovery expert or if you can recover by trying to create a new array, testing it, and then restoring a backup to it (this all on the other system, remember we're trying to isolate variables).

If the controller or drives are damaged, as mentioned above I'd suspect a power surge or PSU failure, not insufficient power. Further testing of the original system without the card & drives may help to isolate this, you don't mention what spare hardware you might have on hand but if you had some old worthless drives lying around they could be used to come close to duplicating the prior load when the array was running from that system.

So far nothing has been mentioned about bench time and fees or downtime related losses. It could be as cost effective to just replace the PSU as wonder about it, same goes for other parts.
February 1, 2007 1:01:45 PM

Thanks for the advice, much appreciated.

** " When you write that you removed each and tested them, what is that supposed to mean? You can't just individually hook up one drive from a RAID5 and expect Windows to help, it would be better to never ever ever do that, windows likes to write to drives if you're not careful what you do." **

i just wanted to make sure the drives themselves were still operational as I was given an error message stating that 4 of my drives were possibly damaged. I wanted to see that windows could still identify the drives.

The data stored on this array is backed up, so I am not concerned with losing its contents, my main priority is to ensure the stability of the sysem.