diskscan - scan a disk for failed and near failure sectors
is intended to check a disk and find any bad sectors already
present and assess it for any possible sectors that are in the process of
going bad. The operation is all read-only and can cause no direct damage to
the data on the disk.
diskscan reads the entire block device and notes the time it took to read a
block. When there is an error it is immediately noted and also when there is a
higher latency to read a block. A histogram of the block latency times is also
given to assess the health of the disk.
The output of diskscan will show any serious errors or very high latency and
will also emit an histogram at the end of the run in the form:
I: Validating path /dev/sdg
I: Opened disk /dev/sdg
I: Scanning disk /dev/sdg
Access time histogram:
above that: 0
I: Closed disk /dev/sdg
This means that all I/Os in this case were between 100 and 600 msec and there
were 120 chunks being read. Current these chunks are 1MB in size.
display verbose information from the workings of the
scan use multiple times for increased verbosity.
Attempt to fix areas that are nearing failure. This
should only be attempted on an unmounted block device and never on an inuse
filesystem or corruption is likely.
, --scan <mode>
Scan mode can be either
, random reduces the chance that the disk will be
able spend time to recover data before we try to access a sector but the seeks
add noise to the latency measurement. Sequential test is the default and
random test is still experimental with regard to its usefulness.
, --size <size>
Set the size in which the
scan will be done, this must be a multiple of the sector size which is
normally 512 bytes.
, --output <file>
Set the output file that
the scan will generate. This is a JSON file with the summary and details about
the exceptional events found during the scan.
, --raw-log <file>
Set the output file for
the raw log which logs everything done and seen during the scan. This is a
rather large file but it can help get the finer details of the scan progress
and the disk behavior during the scan. This is too a JSON file.
Baruch Even \<firstname.lastname@example.org>