1DISKSCAN(1)                      User Commands                     DISKSCAN(1)
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NAME

6       diskscan - scan a disk for failed and near failure sectors
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SYNOPSIS

9       diskscan [options...] block_device
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DESCRIPTION

12       diskscan is intended to check a disk and find any bad sectors already
13       present and assess it for any possible sectors that are in the process
14       of going bad.  The operation is all read-only and can cause no direct
15       damage to the data on the disk.
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17       diskscan reads the entire block device and notes the time it took to
18       read a block. When there is an error it is immediately noted and also
19       when there is a higher latency to read a block. A histogram of the
20       block latency times is also given to assess the health of the disk.
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22       The output of diskscan will show any serious errors or very high
23       latency and will also emit an histogram at the end of the run in the
24       form:
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26           I: Validating path /dev/sdg
27           I: Opened disk /dev/sdg
28           I: Scanning disk /dev/sdg
29           Access time histogram:
30                  1: 0
31                 10: 0
32                100: 0
33                500: 120
34               1000: 0
35               2000: 1
36               3000: 0
37               4000: 0
38               5000: 0
39               6000: 0
40               7000: 0
41               8000: 0
42               9000: 0
43              10000: 0
44              15000: 0
45              20000: 0
46              25000: 0
47              30000: 0
48           above that: 0
49           I: Closed disk /dev/sdg
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51       This means that all I/Os in this case were between 100 and 600 msec and
52       there were 120 chunks being read. Current these chunks are 1MB in size.
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OPTIONS

55       -v, --verbose display verbose information from the workings of the scan
56       use multiple times for increased verbosity.
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58       -f, --fix Attempt to fix areas that are nearing failure. This should
59       only be attempted on an unmounted block device and never on an inuse
60       filesystem or corruption is likely.
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62       -s <mode>, --scan <mode> Scan mode can be either seq or random, random
63       reduces the chance that the disk will be able spend time to recover
64       data before we try to access a sector but the seeks add noise to the
65       latency measurement. Sequential test is the default and random test is
66       still experimental with regard to its usefulness.
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68       -e <size>, --size <size> Set the size in which the scan will be done,
69       this must be a multiple of the sector size which is normally 512 bytes.
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71       -o <file>, --output <file> Set the output file that the scan will
72       generate. This is a JSON file with the summary and details about the
73       exceptional events found during the scan.
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75       -r <file>, --raw-log <file> Set the output file for the raw log which
76       logs everything done and seen during the scan. This is a rather large
77       file but it can help get the finer details of the scan progress and the
78       disk behavior during the scan. This is too a JSON file.
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SEE ALSO

81       badblocks(1), fsck(1)
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AUTHOR

84       Baruch Even \<baruch@ev-en.org>
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88DiskScan 0.20                     2013-10-25                       DISKSCAN(1)
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