From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robert Hancock Subject: Re: MD/RAID time out writing superblock Date: Sun, 20 Sep 2009 12:36:39 -0600 Message-ID: <4AB67637.9060906@gmail.com> References: <4A9BBC4A.6070708@redhat.com> <4A9BC023.10903@kernel.org> <20090907114442.GG18831@arachsys.com> <20090907115927.GU8710@arachsys.com> <20090909120218.GB21829@arachsys.com> <4AADF3C4.5060004@kernel.org> <4AADF471.2020801@suse.de> <4AAE3B9A.2060306@rtr.ca> <4AAE3F86.8090804@suse.de> <4AAE524C.2030401@rtr.ca> <20090916231921.GL1924@arachsys.com> <4AB239C8.2020203@rtr.ca> <4AB25736.1060601@suse.de> <4AB260CA.8040308@rtr.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4AB260CA.8040308@rtr.ca> Sender: linux-kernel-owner@vger.kernel.org To: Mark Lord Cc: Tejun Heo , Chris Webb , linux-scsi@vger.kernel.org, Ric Wheeler , Andrei Tanas , NeilBrown , linux-kernel@vger.kernel.org, IDE/ATA development list , Jeff Garzik , Mark Lord List-Id: linux-ide@vger.kernel.org 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 >