NAME

       diskscan - scan a disk for failed and near failure sectors

SYNOPSIS

       diskscan [options...] block_device

DESCRIPTION

       diskscan 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:
                  1: 0
                 10: 0
                100: 0
                500: 120
               1000: 0
               2000: 1
               3000: 0
               4000: 0
               5000: 0
               6000: 0
               7000: 0
               8000: 0
               9000: 0
              10000: 0
              15000: 0
              20000: 0
              25000: 0
              30000: 0
           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.

OPTIONS

       -v, --verbose display verbose information from the workings of the scan use multiple times for increased
       verbosity.

       -f, --fix 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.

       -s <mode>, --scan <mode> Scan mode can be either seq or random, 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.

       -e <size>, --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.

       -o <file>, --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.

       -r <file>, --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.

SEE ALSO

       badblocks(1), fsck(1)

AUTHOR

       Baruch Even \<baruch@ev-en.org>