What's percentage of free space needs RAID 5 to rebuild after crash?
 

hi

What's percentage of free space needs RAID 5 from a Linux server with 8 HD to rebuild, after a crash of 1 hard disk?
For example, on 1,4 TB RAID 5 is just 10 MB free space.

Your question doesn't make sense, so I am not sure how to answer.

In RAID5 you have your parity spread over all your disks, so if one disk fails you can rebuild with the rest of them. But you can only rebuild if you have another disk of the same size (and best would be same make and model).

In your case (if I understand correctly), one of your three disks (4TB each) died. You now need another disk of 4TB and partition it the same as the other disks.

Here is quick way to copy your partition table over to the new disk from one of the working drives:
http://unix.stackexchange.com/questi...ls/60393#60393

I hope that answers your question.

I forgot to ask (and simply assumed) if you are using mdadm for your RAID. I assume so much because you would otherwise use your hardware controller to rebuild your RAID.

In any case, if you are using mdadm, you will need to add that drive to your RAID ARRAY for the rebuild to start. And don't be surprised if it will take a couple days to finish.

The amount of used vs. free space on a RAID array is irrelevant to its operation.

In other words, you don't need any free space at all, just a new disk that's at least as big as the one that died.

It's mdadm.

If your question points to percent of disk space available on a single disk for data where the disk is configured as a component of RAID 5 configuration, then you can compute it using the formula [(n-1)/n]*100. n can be substituted for the total number of disks in RAID 5 configuration.

Regards.