Protection information and power loss/write failures

Vladislav Bolkhovitin vbolkhovitin at
Fri Feb 28 17:20:37 PST 2014

* From the T10 Reflector (t10 at, posted by:
* Vladislav Bolkhovitin <vbolkhovitin at>
In SPC-4 "Write and unmap failures" section says that on power loss for those
commands, which have not completed when the power loss occurs, data in their
blocks are
indeterminate, i.e. can be "old data, new data, vendor-specific data, or any
combination thereof".
Does it mean that protection information tags after a power loss for such
blocks can
mismatch their data, so subsequent reads from them can legally return tags
mismatch errors?
I'm asking, because it is generally assumed that writing a block on an SBC
device is
atomic, so the question is if this atomicity assumption applies to the PI
tags as well?
Hopefully, not.
The standards are quite ambiguous in this regard, unless I'm missing
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