From: "Bryn M. Reeves" <bmr-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
To: loody <miloody-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: David Laight
<David.Laight-JxhZ9S5GRejQT0dZR+AlfA@public.gmane.org>,
Lars Melin <larsm17-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
"linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
SCSI development list
<linux-scsi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Subject: Re: dummy scsi read or scsi command periodically for external USB Hard Disk
Date: Mon, 7 Jul 2014 17:25:54 +0100 [thread overview]
Message-ID: <20140707162554.GF19630@localhost.localdomain> (raw)
In-Reply-To: <CANudz+s8R3AnxEJ229EwAOOxEk2WZUjMjoE3rwdRM1YM5ZO=og-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
On Tue, Jul 08, 2014 at 12:15:54AM +0800, loody wrote:
> so sg_read will not hammer on the page cache like dd without "iflags=direct"
>
> thanks for your kind help,
The sg_read program (and other programs in sg3_utils) sends a command directly
to the device using an SG_IO ioctl. This bypasses all the caching layers in
the kernel and always results in IO to the device (if it succeeds).
Regards,
Bryn.
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next prev parent reply other threads:[~2014-07-07 16:25 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-05 17:18 dummy scsi read or scsi command periodically for external USB Hard Disk loody
2014-07-07 9:20 ` Bryn M. Reeves
2014-07-07 14:37 ` loody
2014-07-07 14:59 ` Lars Melin
[not found] ` <53BAB5DF.5090606-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2014-07-07 15:06 ` David Laight
2014-07-07 15:39 ` loody
[not found] ` <CANudz+uOS3VVyz6FcHoui8z678R6Xc0CQrdqFRdS5NyfCB59Zw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-07-07 15:51 ` Lars Melin
2014-07-07 15:52 ` Bryn M. Reeves
[not found] ` <20140707155233.GD19630-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org>
2014-07-07 16:15 ` loody
[not found] ` <CANudz+s8R3AnxEJ229EwAOOxEk2WZUjMjoE3rwdRM1YM5ZO=og-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-07-07 16:25 ` Bryn M. Reeves [this message]
2014-07-09 14:15 ` loody
2014-07-07 15:54 ` Alan Stern
[not found] ` <Pine.LNX.4.44L0.1407071147130.871-100000-IYeN2dnnYyZXsRXLowluHWD2FQJk+8+b@public.gmane.org>
2014-07-07 16:13 ` loody
2014-07-07 17:02 ` Alan Stern
[not found] ` <Pine.LNX.4.44L0.1407071258360.871-100000-IYeN2dnnYyZXsRXLowluHWD2FQJk+8+b@public.gmane.org>
2014-07-08 14:58 ` loody
[not found] ` <CANudz+uRd3tRfPN-Fqcj5sSW-xkRSN-gERBP7HhUY_s5gEALbg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-07-08 16:00 ` Alan Stern
[not found] ` <Pine.LNX.4.44L0.1407081149280.1283-100000-IYeN2dnnYyZXsRXLowluHWD2FQJk+8+b@public.gmane.org>
2014-07-08 19:04 ` loody
2014-07-08 19:26 ` Alan Stern
2014-07-09 3:17 ` loody
2014-07-09 8:37 ` David Laight
2014-07-09 13:27 ` loody
[not found] ` <CANudz+tQ4pJFmLTRsHtL=VjuCg30Af+7CpK1qRQM5TwwShoQtA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2014-07-09 14:25 ` Alan Stern
2014-07-09 14:19 ` Alan Stern
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