Device: /dev/sda, 4 Currently unreadable (pending) sectors in Linux.

[Reynaldo Torres]

Hello all,

I would like to know if someone could help to resolve the following error in Linux Red Hat Enterprise 4 and it is as follow:

Device: /dev/sda, 4 Currently unreadable (pending) sectors

Disk /dev/sda: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sda1 * 1 13 104391 fd Linux raid autodetect
/dev/sda2 14 274 2096482+ fd Linux raid autodetect
/dev/sda3 275 19457 154087447+ fd Linux raid autodetect


What should I do in order to resolve this error? Your attention and concern is greatly appreciated. I will give points to best answer and solution.

Thank you so much!

RT

[Marco Wessel]

It appears to be a message from SMART, telling you your drive is starting to develop bad blocks. I suggest ordering a new drive as this is usually a sign of imminent failure.

[Ivan Ferreira · Accepted solution]

http://smartmontools.sourceforge.net/faq.html

Disk drives store data in blocks (sectors) of 512 bytes. Each 512 bytes has additional bytes appended to it (usually 40 to 60) which are used internally by the disk firmware for error checking/detection and correction. These are called ECC bytes.

Sometimes the data in a sector gets corrupted. This can happen because a speck of dust scratched the disk, or because the disk was powered down while writing data to that sector, or for other reasons. Usually the ECC bytes can be used to correct the corrupted data. However if the ECC bytes are inconsistent or can't be used to correct the bad data, then the 512 bytes of data are lost. Such a sector is called unreadable or uncorrectable.

If your disk has an unreadable sector, this means that some of your data can't be retrieved. You can force the disk to replace the unreadable sector with a spare good sector, but only at the price of losing the 512 bytes of data forever.

Disks with uncorrectable sectors can often be repaired by using the disk manufaturer's 'disk evaluation and repair' utility (see previous FAQ entry). Beware: this may force reallocation of the lost sector and thus corrupt or destroy any file system on the disk. See Bad block HOWTO (http://smartmontools.sourceforge.net/badblockhowto.html#rfile) for generic Linux instructions.

Normally when an uncorrectable sector is found, the disk puts this onto a 'pending sector list' to indicate that it should be replaced with a spare good sector. However this replacement won't take place until either the disk can read the data on the bad sector, or is commanded to write new data to that bad sector.