Re: [smartmontools-support] Blocks missing from disk

[Jim P. <ji...@jt...>]

Richard and Monica Bland wrote:
> I have 6 WDC WD5000AAKS 500GB disks in a Software RAID 5 array under
> Linux. The machine was recently power cycled to change a PSU and on
> reboot sda was bumped from the RAID array and would not re-add.
>
> It turns out the disk has 'shrunk' :
..
> I'm assuming this is due to 57 bad blocks 'known' to the disk and
> therefore the disk is reporting fewer available blocks to Linux.

Hi Rich,

Disks don't do that.  Bad blocks are reallocated from a spare area on
disk, and that's why there are a limited number of reallocations that
can occur.

The problem must lie elsewhere -- maybe something like HPA (host
protected area) enabled on the disk by the BIOS, or maybe some driver
issue.  The full dmesg output from boot would be the best place to
track that down.

> However, the disk is reporting no errors to smartctl. I've run the Short
> and Extended offline tests and these both give "Completed without
> error". Can smartctl 'prove' that the disk has bad blocks prior to me
> RMAing the disk?

Full "smartctl -a" output would show any reallocations that occured,
although if the extended offline test is successful than it's likely
the disk does not need to be returned.

-jim