SSD EOL Write Protect query

Gerry Houlder gerry.houlder at seagate.com
Thu Jan 16 14:36:37 PST 2014


Formatted message: <a href="http://www.t10.org/cgi-bin/ac.pl?t=r&f=r1401164_f.htm">HTML-formatted message</a>

I am aware of other products that can put themselves into a write protected
condition when they believe their write mechanism is unreliable and should
be disabled to prevent loss of data. This is an error recovery/ reliability
preservation activity and not normal device behavior, so it need not be
discussed in the standard. I think your proposed use falls into the same
category.
As far as returning a Unit Attention, that would not be useful. Getting
WRITE PROTECTED sense data on every write command is more than sufficient.
On Wed, Jan 15, 2014 at 5:27 PM, Mike Berhan <mikeb at bustrace.com> wrote:
> * From the T10 Reflector (t10 at t10.org), posted by:
> * Mike Berhan <mikeb at bustrace.com>
> *
> The SBC-3r36 specification has a "Write Protection" section which states
> that write protection is controlled by one of the following:
>
> a) the user of the medium through manual intervention (e.g., a mechanical
> lock on the SCSI target device);
> b) hardware controls (e.g., tabs on the medium's housing); or
> c) software write protection
>
> For hardware write protection, it also states:
>
> "Hardware write protection results when a physical attribute of the SCSI
> target device or its medium is changed to specify that writing shall be
> prohibited. Changing the state of the hardware write protection requires
> physical intervention, either with the SCSI target device or its medium."
>
> I cannot find a discussion of the drive putting itself into a write protect
> state without manual or software intervention.  For example, an SSD that is
> approaching its end of life might be running out of reserved free blocks
> and
> will put itself into a write protect state.  If a drive fails this state, I
> could see writes failing with returned sense data of:
>
> 07h 27h 05h (Data Protect - Permanent write protect)
>
> Now to my question.  If a drive enters, on its own, this write protect
> state, has it also entered a unit attention condition?  I'm assuming it
> should.  If it has, what is the unit attention that should be returned to
> be
> SBC-3 compliant?
>
> Thanks in advance.
>
> Mike
>
>
>
> *
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