Messages in this thread | | | Date | Sun, 20 Sep 2009 12:36:39 -0600 | From | Robert Hancock <> | Subject | Re: MD/RAID time out writing superblock |
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On 09/17/2009 10:16 AM, Mark Lord wrote: > Tejun Heo wrote: >> Hello, >> >> Mark Lord wrote: >>> Tejun.. do we do a FLUSH CACHE before issuing a non-NCQ command ? >> >> Nope. >> >>> If not, then I think we may need to add code to do it. >> >> Hmm... can you explain a bit more? That seems rather extreme to me. > .. > > You may recall that I first raised this issue about a year ago, > when my own RAID0 array (MythTV box) started showing errors very > similar to what Chris is reporting. > > These were easily triggered by running hddtemp once every few seconds > to log drive temperatures during Myth recording sessions. > > hddtemp uses SMART commands. > > The actual errors in the logs were command timeouts, > but at this point I no longer remember which opcode was > actually timing out. Disabling the onboard write cache > immediately "cured" the problem, at the expense of MUCH > slower I/O times. > > My theory at the time, was that some non-NCQ commands might be triggering > an internal FLUSH CACHE within the (Hitachi) drive firmware, which then > caused the original command to timeout in libata (due to the large amounts > of data present in the onboard write-caches). > > Now that more people are playing the game, we're seeing more and more > reports of strange interactions with smartd running in the background.
Well, unless the SMART commands are using a non-standard timeout, it'll be the same as the timeout for the flush cache, so the flush cache would have timed out too..
> > I suspect more and more now that this is an (avoidable) interaction > between the write-cache and the SMART opcode, and it could perhaps be > avoided by doing a FLUSH CACHE before any SMART (or non-data command) > opcode. > > Cheers > -- > To unsubscribe from this list: send the line "unsubscribe linux-scsi" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >
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