230W PSU enough for 4-5 drives

[acgraham]

After some hardcore problems i had the other week with my machine i decided to wipe the dust off my old pIII 800 and set it up as a backup server. using an Adaptec Raid card and setup raid 5. i've currently only got 2 SATA WD2000JB (or d cant remember) drives in there mirrored and an old ide for the OS. But if i plug in another 1 or 2 drives, will my 230W old PSU be able to deal with it?

Im not running anything else in there, a really old video card, and im guessing the CPU wouldn't take up much power. i have intentions to put a dual layer DVD burner in there though. what do you guys think?

I also bought an 800W ups to run both my systems off.

[GrahamGarside]

Well a PIII uses the 3.3V line for power meaning the 12V line should be pretty much all available for drives

A drive uses about 15W power at most, 5 drives are gonn need about 7A from the 12V line, so I'd say as long as the 12V line is rated to around 10A continuous and not just peak, you should be ok

[surlyjoe]

what brand of PSU is it? some of the old 235's are as good or better than what they are callin a 450w these days

[acgraham]

Its an AOpen FSP235 - 60AT. the 12V line is rated to 8A it says on the side.

[GrahamGarside]

A dvd writer as well is going to be pushing it as they use about 2A

[Aedan]

The highest current draw is always at startup, when the drives are spinning up. As long as your PSU can handle a potential brief overload at this point, you should be ok.

The SATA drives you currently have use about 0.53A (6.25W) on the 12V line when they're active. If you had five of those drives, you'd be looking at under 3A (36W) required from the 12V line.

An 8x DVD writer such as the Pioneer DVR-A07XL requires 0.8A on the 12V line.

[Gizmo]

Some drives provide the option to 'delay start'. This is common in the SCSI world, I don't know if your SATA drives have this option or not. I've got my drives set to not even start unless the SCSI controller comes up. The SCSI controller BIOS then starts the drives 2 at a time at 6 second intervals in order to reduce the surge load on my PSU.

[acgraham]

hmm im pretty sure i cant do that with my drives. ive got the box plugged into a ups and when i turn the machine on the load goes up 25%. being a 800W ups i guess that means its sitting on about 200W. if i just say to hell with it and plug everything in, could i actually cause damage to my hardware other than the power supply? because if its just the power supply that dies ill have to buy a new one anyway, and then i will have answered my question. hehe.

[Gizmo]

The most likely failure mode would probably not cause damage, but it is possible.

[noorman]

A good PSU would cut out when a rail is goi,g in overcurrent !


Just try it, you can do a step-by-step, with 1 then 2, then 3 drives ...

[acgraham]

well il just forget about the dvd burner, but by the sound of this 4-5 hardrives might work. hope i dont kill them though if i overload the machine

[noorman]

Originally Posted by acgraham

well il just forget about the dvd burner, but by the sound of this 4-5 hardrives might work. hope i dont kill them though if i overload the machine

You could do the calculations here, to double-check:

http://www.jscustompcs.com/power_sup....php?cmd=INTEL

[acgraham]

Originally Posted by noorman

A good PSU would cut out when a rail is goi,g in overcurrent !


Just try it, you can do a step-by-step, with 1 then 2, then 3 drives ...

so how will i know if it cuts out properly without damaing my hardrives?

[GrahamGarside]

Originally Posted by noorman

You could do the calculations here, to double-check:

http://www.jscustompcs.com/power_sup....php?cmd=INTEL

The only problem with that is it doesn't make any allowances for differant voltage rails.
For my A64 system it recomends a 268W PSU, which apart from a shuttle system, I know of no psu's with that low a power output that have a 12V rail that can handle a Newcastle and 6800 based system