I have every 30 minutes smartd messages on /var/log/messages:
smartd[3588]: Device: /dev/sdc, 176 Currently unreadable (pending) sectors
This drive (sdc) is part of RAID 5 configured with mdadm.
Mdadm monitor tells RAID is ok but i want to know if i need to change the drive or not. Also if its neccesary to mark as bad this sectors or OS already did it.
If i need to change the drive, how can i chose the replacement one? I canĀ“t find the number of blocks in hard drive specifications so if i chose one with less blocks than original, i will be in trouble.
Thanks.
Best Answer
Yes, change the drive.
Unreadable (pending) sectors are sector whose contents could not be read. On a normal non-RAID situation that would result in either a read error, or a long delay while the drive attempts to read the sector again and again until it succeeds (or until it eventually gives up).
With RAID two things are happening:
What you want to do is:
smartctl -a /dev/sdc
. Do not assume all drives of size X have the same capacity. Manufacturers like round numbers; one 500GB drive might well be smaller than another 500 GB drive.mdadm --manage --remove /dev/mdX /dev/sdc
)mdadm --add /dev/mdX /dev/sdc
)If you used large disks then this will take a lot of time. Sometimes it is faster to just rebuild the RAID array from scratch and restore from backups. (TEST those backups first!)
While the RAID is rebuilding you have no redundancy. Thus is another disk fails (e.g. due to the stress of rebuilding) then you have a problem. This sometimes happens with large disks (long rebuild times) and batches of drives from the same date.