Re: dummy scsi read or scsi command periodically for external USB Hard Disk

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hi Alan:

>> > E.g. issue an sg_read for one sector to the device every 4m:
>> >
>> >   */4 * * * * sg_read count=1 if=/dev/<disk>
>> Since my target platform arm embedded system,
>> does that mean I should include sg_read in my Busybox
>> or
>> cross-compile sg_read from sg3_utils?
>
> An alternative is to write a positive value, such as 240000, to
>
>         /sys/block/sdX/events_poll_msecs
>
> where X is replaced with the proper drive letter.  (240000 ms = 240 s =
> 4 m.)  I'm not sure this will work, but it's worth a try.

I cannot find events_poll_msecs you mentioned in my system.
Is this capability related to kernel version?
( my kernel version is 2.6.38.8 )

Sincerely appreciate all yours kind help,

PS:
below is result of /sys/block/sdb/
/sys/block/sdb# ls -lht
total 0
-r--r--r-- 1 root root 4.0K 2014-07-08 00:08 alignment_offset
lrwxrwxrwx 1 root root    0 2014-07-08 00:08 bdi ->
../../../../../../../../../../virtual/bdi/8:16
-r--r--r-- 1 root root 4.0K 2014-07-08 00:08 capability
-r--r--r-- 1 root root 4.0K 2014-07-08 00:08 dev
lrwxrwxrwx 1 root root    0 2014-07-08 00:08 device -> ../../../3:0:0:0
-r--r--r-- 1 root root 4.0K 2014-07-08 00:08 discard_alignment
-r--r--r-- 1 root root 4.0K 2014-07-08 00:08 ext_range
-r--r--r-- 1 root root 4.0K 2014-07-08 00:08 inflight
drwxr-xr-x 2 root root    0 2014-07-08 00:08 power
-r--r--r-- 1 root root 4.0K 2014-07-08 00:08 stat
drwxr-xr-x 2 root root    0 2014-07-08 00:08 trace
drwxr-xr-x 2 root root    0 2014-07-08 00:05 holders
drwxr-xr-x 3 root root    0 2014-07-08 00:05 queue
-r--r--r-- 1 root root 4.0K 2014-07-08 00:05 range
-r--r--r-- 1 root root 4.0K 2014-07-08 00:05 ro
drwxr-xr-x 5 root root    0 2014-07-08 00:05 sdb1
-r--r--r-- 1 root root 4.0K 2014-07-08 00:05 size
drwxr-xr-x 2 root root    0 2014-07-08 00:05 slaves
-r--r--r-- 1 root root 4.0K 2014-07-08 00:05 removable
lrwxrwxrwx 1 root root    0 2014-07-08 00:05 subsystem ->
../../../../../../../../../../../class/block
-rw-r--r-- 1 root root 4.0K 2014-07-08 00:05 uevent
/sys/block/sdb#
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