Question about RAID(5)

First some background: A dude brings me his PC 'cuz it's not powering up. The PSU tested "dead" so I swapped it for a brand new unit. Now, after the PSU has been completely connected to the MB, HDDs, CDs, etc, and the power is plugged in to the PSU, as soon as the main switch on the PSU is turned on, the PC powers on, the fans spin, etc, without needing to press the power button on the case, but there's no "BEEP" and no video. After much diagnosing and part swapping, it is discovered the MB has failed also (which I had assumed right when it powered on w/o requiring the use of the power button on the case). He was running a RAID1 (mirrored) on drive(s) C: using the MB SATA connectors (it was two 250gb SATA drives being cloned in real-time; Windows sees it as a single 250gb drive; but you knew that already) and he was running Server 2003 Std. So I swapped the mobo, performed a repair install of Server2003 on a single drive from his mirrored RAID (on drive C: ) and that went perfectly fine (I left the 2nd drive from the mirrored RAID alone just in case something went wrong). I installed the drivers for the new MB, and all is well. It is at this point that I am told "out of the blue" that he's running RAID5 on the other 3 drives that were previously connected to an Adaptec AAR-1420SA card. Yeah- I saw the card and the drives, but since they weren't mentioned as being anything special, I assumed they were just individual drives and it wouldn't matter how they were connected to the Adaptec card, so I paid no attention as to what drive plugged in to what header on the Adaptec card when I took everything apart to install the new motherboard. Anyway- I powered down, unplugged the power cord, put the RAID card in a PCI slot without the drives connected and powered up and booted to the desktop; Windows recognized and installed the Adaptec RAID card. I powered down, unplugged the power cord, and connected the drives to the card. Since there's several combinations of which drive can plug in to which header, I made a 'chart' of all possible combos and figured "if combo 'A' doesn't work, I'll try combo 'B', if 'B' doesn't work...." and so on. So, after trying all possible combos, the RAID never came up correctly. I guess my question is this: is it possible to lose data from a 3 drive RAID5 if the drives are connected in a different order compared to how they were connected when then RAID5 was set up? Is it possible to destroy the RAID5 by doing this? The dude is implying that I destroyed his RAID and all his data is "gone forever" (his words). I figured it's a miracle that drive C: wasn't all messed up from the bad mobo, the bad PSU, and the fact that he has been running a total of 5 hard drives, 2 optical drives, a zip drive, a floppy drive, 2x512mb DDR, a P4 3ghz CPU, AGP video card, all from a "no name" 250w power supply, and he ran it this way for 2-3 years until the PSU failed (and probably took the MB with it), and then he brought it to me. Now, if I had been informed that the Adaptec card was supporting RAID5, I would have noted which drive plugged in to what connector, and I probably should have asked.... but, again, if 3 RAID5 drives are plugged in to different headers from where they were plugged in when the RAID was configured, is the data lost? How can we figure out which drive was "first" and which was "second" and which was "third"?
:confused

THANKS!!!

 

You might check further on this to be exactly correct, but RAID5 needs 4 HDs to run correctly. I'm not an expert, but running it with 3 drives will get some flakiness if it runs at all. The info I read about RAID stated that in any config, the hard drives need to be even. 2,4,6,8 as the RAID array goes up in number.

 

Well, RAID5 does indeed run with odd numbers of drives, including 3, but like most RAID set ups, it's "happier" with even numbers: 4, 6, etc. It turns out that the Adaptec card doesn't even support RAID5!!! The owner of the PC did not know this, I didn't know it either until I did some research last night. The RAID5 was actually a software RAID configured using the Adaptec software, the software RAID is then somehow communicated to the controller card and the data is written however the software determines to be best. So, this means that it doesn't matter which drive is on header A, or header B, 'cuz the software (not the hardware) determines which drive gets what data and it doesn't care if the drives are connected one way, then swapped out. After messing with the software for a bit, I discovered a "re-activate RAID" option, I clicked it, and it kicked in to "re-sync" mode, so ALL IS WELL!!!!!!!
:celebrate :dood

Thanks for the input dee2too.... every bit helps!

 

Wow dbl & Halo "exploring" an issue....... had to join.

 

From what I have heard (RAID0 for 4yrs) RAID10 gives parity plus stripping?

 

Yeah. You should have seen the surprised look on the PC owner's face when I told him the Adaptec card didn't natively support RAID5! Priceless! roflmao Luckily, even if the RAID had completely failed, he had backup on an external drive. He has scheduled auto-backups every 24 hours, so at least a current backup was available should a worst-case-scenario occur. As to the speed, from what I read, a RAID5 setup offers limited performance increase, especially in this scenario where it was a software RAID. So why would someone choose this type of setup? What are the benefits of a RAID5 setup? I understand the pluses of mirrored and/or striped RAIDs, but something like RAID5 I just can't wrap my brain around it....