WRITE_AND_VERIFY doubt

Konrad Rzeszutek konrad at virtualiron.com
Fri May 8 09:50:11 PDT 2009


* From the T10 Reflector (t10 at t10.org), posted by:
* Konrad Rzeszutek <konrad at virtualiron.com>
*
On Fri, May 08, 2009 at 12:52:28PM -0300, Flavio Junior wrote:
> Hi folks, afternoon.
> 
> I've a tad doubt when writing a simple code to sends a WRITE_AND_VERIFY
> (0x2E) command to a scsi device.
> 
> I need to do it to decide if this is a primary (and read-write) storage or
a
> secundary (and read-only) storage (ibm ds4700), and adjust my I/O MultiPath
I was under the impression that the DS4700 was an RDAC device. Meaning
you can use these settings:
 device {
	vendor		"IBM"
	product 	"1814"
	hardware_handler    "1 rdac"
	path_grouping_policy	group_by_prio
	prio		"rdac"
	failback	immediate
	path_checker	    rdac
    }
And it will detect whether your secondary paths are not in usage and
call them 'ghost'.
> priority accordingly, and i need to run it periodically to check if the
> roles change.
> 
> My doubt is, is there a area that I cant safety use this command without
> risk to corrupt the data on disk? I'm not a really developer, just make
some
You will cause corruption.
> researches and read some codes to assembly my own, here is the code:
> http://pastebin.com/m22b06f04
> 
> 
> O course, if there is a way more elegant to get this info I'll appreciate
if
> someone says me. :)
I think using the right multipath.conf entry should do it.
> 
> 
> Really thanks in advance and some sorries for english and dumb question.
> 
> 
> --
> 
> Flávio do Carmo Jùnior
> Florianopolis/SC, Brazil
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