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

[Lars Melin <larsm17@gmail.com>]

On 2014-07-07 21:37, loody wrote:
> hi Bryn:
>
> 2014-07-07 17:20 GMT+08:00 Bryn M. Reeves <bmr@redhat.com>:
>> On Sun, Jul 06, 2014 at 01:18:03AM +0800, loody wrote:
>>> hi all:
>>>      we met a USB Hard Disk that will go to suspend if host stop
>>> sending scsi command over 5mins.
>>>      To save the IO, kernel will keep the file in page cache as much as
>>> he can and under this circumstances, the scsi command may disappear
>>> for a while longer enough to cause the device suspend.
>>>
>>>      is there any kernel config or module parameter can do the dummy
>>> read or scsi command periodically?
>> No but you could set up a simple cron job to call an sg3_utils command.
>>
>> 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?
>
> appreciate your kind help,
> --
> To unsubscribe from this list: send the line "unsubscribe linux-usb" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
sgread is not included in BusyBox but you should have "touch".
Create a dummy file on the disk and let cron touch it every 4 minutes.