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I am not configured hot spare and i configured software raid using mdadm .when i execute command mdadm --detail /dev/md3 it showing one device is failure and even i removed that drive and checked in other computer but it is not detecting.Now i have one more new 500gb hard disk .Now i need to be replace new drive in the place of faulty drive. Give me procedure to replace faulty with new and Recover data
If you are able to read and write to the raid device, then you will be able to rebuild a new drive in place of the faulty one. The parity segments are being used to recover the original data were needed in the mean time.
If you have a 4 disk RAID-5, and you lose two disks, leaving only two remaining, you will generally not be able to recover the data from it. RAID-5 protects againsts single disk failure, but you would need to have RAID-6 to protect against double disk failure (basically there are two parity blocks written instead of one, so you lose two disks worth of capacity instead of one).
thanks btmiller, but my question is if i confiured raid 5 using 3 drives in that 1 drive got failure .In that time i can access,modify files in two drives only know for time beging ??? Later i can add New drive with the place of faulty drive is it possible know???
Yes, using raid 5, the array is usable with two disks. RAID-5 works by storing the XOR of the data of two disks on the third. Each of the disks has areas used for xor parity. You don't have a single disk reserved for parity.
If disk 3 is bad, and the disk 2 has a parity bit, the device will xor the byte from disk 1 with the parity byte from disk 2 to recover the data that was in disk 3.
If you used 4 disks, the remaining disks are xor'ed as well.
While one disk is absent, you are in danger because if another disk goes ofline, you are in trouble. One problem with RAID-5 is if there is an area on one of the remaining disk that has undetected read errors. Maybe that file hasn't been read for years. The area will be read when you try rebuilding the array.