Re: MD/RAID time out writing superblock

Tejun Heo
2009-09-17T15:48:32Z

Hello,

Mark Lord wrote:
>> That's interesting. One important side effect of issuing IDENTIFY is
>> that they will serialize command streams as they are not NCQ commands
>> and thus could change command patterns significantly.
> ..
>
> SMART is the opcode that is most frequently implicated here, not IDENTIFY.

Yeap, any non-NCQ commands would do it.

> Note that even a barrier FLUSH CACHE is non NCQ and will serialize
> the stream.

Yeah, I was just thinking that issuing non-NCQ commands mixed with NCQ
commands would make the command stream fluctuate more. Modern drives
are pretty good at lowering power consumption while idle so being more
fluctuative (is it a word?) might have something to do with the
problem. Just a wild speculation tho.

Thanks.

--
tejun