Hard Drive Enclosure and PSU Question?

B

BricRoth

Limp Gawd
Joined
Apr 22, 2002
Messages
196
If this has been discussed I am sorry but with the disabled search I cant seem to find it. I am needing to ad some space to an existing server. Its configuration is 2 raided scsi drives for the OS Drive (mirrored), And 5 Scsi drives in a raid 5 array for the data drive. I really need some extra storage and have considered adding a sata raid card and 2 200 gig sata drives in mirror for storage. This storage would be accessed only by 2 people not the entire photography studio. The ability to drag data across the sata channel instead of the network is atractive for speed sake. My concern is the extra load on the redundant psu's. So I am considering and external enclosure to house the 2 drives (maybe more in the future). I am questioning the PSU. Can I modify an atx psu to power up the hd's when there is no Motherboard present? Is this a good idea or am I missing something? Even the rackmounts I have looked at are set for atx motherboards.

Thanks for you help as always.

Bric
 
Ive done that
the trick is synchronizing the PSUs or all sorts of hell will break loose, there are two effective ways
Hardwired or Relay
Ive been using the hardwire version without issue for 3 years now
(dual 400 watt PSUs (older), one for the mobo, the other for 12 to 6 HDDs)

but generally speaking Id think an N+1 redundnant would handle the extra drives, what power supply do you have?

Ive also run the same setup off a 460watt Zippy N+1
 
The Hardwire sounds interesting. I am at home for the weekend and wont be able to look at the redundant psu's till monday morn again. I do know there are two in this particular server. (I didn't build this one though it was there when i arrived)

Let me ask this question another way. If I wanted to house 2-5 HD's in another case next to the server and just run the sata ribbons back to the main server what would I have to do to an ATX psu in the external case to get it to power just the hd's? Since I would not have a Motherboard in this case the PSU I assume wont power up without jumper conected. Any how to's on jumping the atx to and on/off for HD's only?

Thanx.
 
at that remove Id do the relay
all it takes to turn on an ATX is connecting the green (power good) to the black (ground) but if the HDDs dont power up and down when the OS expects them to file corruption will result so synching the PSU is a good idea
ATA isnt hotswap compatible (without extra hardware or software)
 
I was able to put 8 hard drives into my machine and run them and the PC off of the 300watt PSU.
5 7200 rpm drives and 3 10K rpm drives.

Only issue I have is that the 5v side is reading 5.7volts. and I have to hit F1 to continue booting. This is my fileserver so I only reboot it when I update software on it that requires a reboot.
 
Originally posted by WS6
so I only reboot it when I update software on it that requires a reboot.
Click to expand...

and therein is the rub

the main reason someone would require a larger PSU is at startup
where spinning up the drives really puts a strain on the 12v amps

most SCSI drives have the delayed startup option, to avoid that

might want to review these
voltage regulation & transient resopnse long thread backtrack as well
takaman's Power Supply Calculator rev0.63
Choosing the Right Power Supply (properly calculating your amp needs)
[H]ardcore PSU info < important

calculators are a little misleading, they are based on the maximum draw of all the components, something that rarely if ever happens (runtime power requirements are generally half), but you offset that against the overestimates many PSU manufactrers claim for the amps per rail of their PSUs, either by testing combined rails seperately and almost always by testing at a temperature that its unrealistic to reproduce in a computer (25C)

so it sort of equals out, but realistically its at startup that the critical power is required, especially with lots of drives
if you can delay spinup, you can get by with alot less

it used to be that it was amp starvation (because the PSU where sold primarilly by watts and the amp rails deceptive figured) that fouled people up, but with the speed increases in the FSB, its now the rail stability, and the transient response that has become critical, to a large extent the quaility of the power regulation on the mobo enters into the picture mitigated by the quality of the power supply, so it gets even more complicated to qualify it, where one person states: Ive had no problems with PSU X and the next with the same PSU fries RAM on a regular basis, and wonders why

after improper installation (ESD precautions) poor power is the leading cause of premature failure (according to RAM manufacturers)

also monitoring your rails via the SMBus is falsely reassuring
useful but flawed (see the last link for dynamic load, multimeter readings, especially note the startup instability in most PSU)
 
Originally posted by Ice Czar
and therein is the rub

the main reason someone would require a larger PSU is at startup
where spinning up the drives really puts a strain on the 12v amps

most SCSI drives have the delayed startup option, to avoid that
Click to expand...

I am going to read the links you posted.
I do have the SCSI drives on delay start, they only spin up when the controller is scannning each ID, the 3 IDE drives spin up on power up.
 
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