4 x 1 TB in raid5 will give you 3 TB net space, not 2.7 or 3.2. It gives you (4 -1) x 1 TB net space. Of course there is a difference between 1000 and 1024, the first being used by disk manufacturers and the second by all OS'es.
Was it the system that broke or the raid, because in the latter case a simple disk replacement would have corrected the situation without data loss. If it was the CPU or mobo, reattaching the disks would have safeguarded your data as well, so what happened?
If you had 3.2TB showing available on your 4 drive raid 5 then you had corruption or something not setup right somewhere. Did you run a full initialization of the raid 5 before when you created the array or did you select quick? 2.7TB sounds about right after you create the partition on the array. 3.2TB was definitely not right with 4x 1TB drives in a raid 5.
My brother who had been a system admin assembled my PC, set up the raid 5, and installed W7.
He did not format D: and it came up (as far as I can remember) at 3.2TB.
I brought the PC home and it would not even start up.
My brother concluded that the drive home had wrenched the mobo so I returned it for a new one.
My brother installed the new mobo remembering the sequence in which the drives were connected to the mobo and the PC came to life with 3.2TB.
I used it every day for a month putting at least 500MB video data on D:.
Then I had trouble loading video files onto D: and later I noticed that my RAM was down from 12GB installed to 8GB.
It was not a USB or Firewire problem because I could not move files from C: to D:.
The 1st huge file would start moving quickly then slow down as though someone were applying the brakes.
The 2nd file would start slow and stay slow.
I brought it to a local PC shop and they concluded that my mobo was broken again so I returned it to ASUS.
When I got my 3rd mobo the shop installed it and the PC came up with no data and D: = 2.7TB.
It may have been that the shop knew more about setting up raid 5 than I do.
The file transfer problem is gone.
The data lost is not important since all those projects were finished.
They also told me that one of my RAM sticks is broken so I returned it to Crucial.
So now it may have been the one broken RAM stick that was causing the problem all along.
After 20 hours my formatting of D: is a little less than half done.
I am hopping it will be done sometime tomorrow.
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It sounds like the ram corrupted the volume data on the original raid then. 3.2TB was definitely not right. Sounds like you have a clean raid volume at 2.7TB now.
Is it OK to stop the format process long before it is finished?
NO. It takes time but let it finish.
cant believe no one has said this....
1)you do not do raid 5 with onboard raid your IT brother should know better.
2) with any onboard raid you need an external back up and really even with a good raid array you should back it up as well.