From mboxrd@z Thu Jan 1 00:00:00 1970 From: TomK Subject: Re: [ LR] Kernel 4.8.4: INFO: task kworker/u16:8:289 blocked for more than 120 seconds. Date: Sun, 30 Oct 2016 17:08:46 -0400 Message-ID: <6da81a22-8a07-7e6f-cd93-ddc5a97b2366@mdevsys.com> References: <73e35e17-80aa-c7e6-535c-3665d9789e16@mdevsys.com> <20161030201302.GB6727@metamorpher.de> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20161030201302.GB6727@metamorpher.de> Sender: linux-raid-owner@vger.kernel.org To: Andreas Klauer Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 10/30/2016 4:13 PM, Andreas Klauer wrote: > On Sun, Oct 30, 2016 at 02:56:58PM -0400, TomK wrote: >> So the question is how come the mdadm RAID did not catch this disk as a >> failed disk and pull it out of the array? > > RAID doesn't know about SMART. It's that simple. > > If SMART already knows about errors - too bad, RAID doesn't care. > It also doesn't know about anything else really. You ddrescue the > member disk directly and it finds tons of errors... RAID isn't involved. > > RAID will only kick when it by itself stumbles over an error that does > not go away when rewriting data. Or when the drive just doesn't respond > anymore for an extended period of time. And that timeout is per request > so a bad disk can grind the entire system to a halt without ever kicked. > > ddrescue has this nice --min-read-rate option, any zone that yields data > slower will be considered a hopeless case, RAID does not have such magic. > If your drive always responds and always claims to successfully write > even when it doesn't, then RAID will never kick it. > > If you never run array checks or smart selftests, errors won't show. > RAID will show them as healthy, SMART will show them as healthy, > doesn't mean diddly-squat until you actually test it. Regularly. > > Kicking drives yourself is quite normal. RAID only does so much. > This is why we have mdadm --replace, that way even a semi-broken disk > can help with the rebuild effort and bad sectors on other disks won't > result in an even bigger problem, or at least, not right away. > > If you leave RAID to its own devices, it has a much higher chance of dying > than if you run tests, and actually decide to do something once *you're* > aware that there are problems that RAID itself isn't aware of. > >> On a separate topic, if I eventually expand the array to 6 2TB disks, >> will the array be smart enough to allow me to expand it to the new size? > > Yes. Perhaps after an additional --grow --size=max. > > Regards > Andreas Klauer > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Very clear. Thanks Andreas! -- Cheers, Tom K. ------------------------------------------------------------------------------------- Living on earth is expensive, but it includes a free trip around the sun.