Flavio Junior billpp at gmail.com
Fri May 8 11:33:39 PDT 2009

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Very interesting points Frederick, really thanks..
I'd tried the read-only bit before, seems don't work, but i'll do it again
with more attention. And others ideas should work. Thanks again :).
I'll post results here.
Flávio do Carmo Júnior
Florianopolis/SC, Brazil
On Fri, May 8, 2009 at 1:40 PM, Knight, Frederick <
Frederick.Knight at netapp.com> wrote:
>  Why don't you just look at the read only bit?  Does the IBM ds4700 not
> report the read only bit for a read only device?  It's the WP bit in the
> mode page header.  Just use MODE SENSE on your favorite mode page to check
> it.
> And no, there isn't any "reserved" space you can write to and be safe.
> Another choice would be ORWRITE (and don't "or" in any bits), or XDWRITE
> (and don't "xor" in any bits).  These would all be ways to "write" without
> changing the data in the LBA (although it is possible the device could
> optimize the write step into nothingness).
>     Fred Knight
>  ------------------------------
> *From:* Flavio Junior [mailto:billpp at gmail.com]
> *Sent:* Friday, May 08, 2009 11:52 AM
> *To:* t10 at t10.org
> *Subject:* WRITE_AND_VERIFY doubt
> 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 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
> 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. :)
> Really thanks in advance and some sorries for english and dumb question.
> --
> Flávio do Carmo Jùnior
> Florianopolis/SC, Brazil

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