Re: Fedora 20 RAID 6 errors on rebuild / check / repair

["Wilson, Jonathan" <piercing_male@hotmail.com>]

On Thu, 2014-07-24 at 09:33 +0200, Kay Diederichs wrote:
> On 07/24/2014 04:29 AM, George Rapp wrote:
> > Hi -
> > 
> > I have a Fedora 20 media server / MythTV backend utilizing a HighPoint
> > RocketRAID 2720SGL controller (Amazon product link:
> > http://is.gd/yqo2i1). The server performs fine under normal (minimal)
> > read-write operations, but during any high-I/O operations (rebuild
> > after mdadm --add, RAID check initiated by "echo check >
> > /sys/block/md6/md/sync_action" or "echo repair > ..."), I get sporadic
> > errors and poor performance on my RAID 6 array, /dev/md6.
> > 
> > Wondering if there is anything I can tweak to make my configuration
> > more stable. The inability to check or repair this RAID device has me
> > nervous.
> > 
> > The problems seem to start when I see the following error message in
> > /var/log/syslog:
> > 
> >> Jul 22 21:23:37 backend3 kernel: [95876.375990] ata5.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
> >> Jul 22 21:23:37 backend3 kernel: [95876.376153] ata5.00: failed command: READ DMA
> >> Jul 22 21:23:37 backend3 kernel: [95876.376284] ata5.00: cmd c8/00:08:40:11:81/00:00:00:00:00/e3 tag 11 dma 4096 in
> >> Jul 22 21:23:37 backend3 kernel: [95876.376284]          res 40/00:00:00:4f:c2/00:00:00:00:00/40 Emask 0x4 (timeout)
> >> Jul 22 21:23:37 backend3 kernel: [95876.376750] ata5.00: status: { DRDY }
> >> Jul 22 21:23:37 backend3 kernel: [95876.376874] ata5: hard resetting link
> >> Jul 22 21:23:37 backend3 kernel: ata5.00: exception Emask 0x0 SAct 0x0 SErr 0x0 action 0x6 frozen
> >> Jul 22 21:23:37 backend3 kernel: ata5.00: failed command: READ DMA
> >> Jul 22 21:23:37 backend3 kernel: ata5.00: cmd c8/00:08:40:11:81/00:00:00:00:00/e3 tag 11 dma 4096 in
> >>          res 40/00:00:00:4f:c2/00:00:00:00:00/40 Emask 0x4 (timeout)
> >> Jul 22 21:23:37 backend3 kernel: ata5.00: status: { DRDY }
> >> Jul 22 21:23:37 backend3 kernel: ata5: hard resetting link
> >> Jul 22 21:23:40 backend3 kernel: [95878.742281] ata5.00: configured for UDMA/133
> >> Jul 22 21:23:40 backend3 kernel: [95878.742413] ata5.00: device reported invalid CHS sector 0
> >> Jul 22 21:23:40 backend3 kernel: [95878.742542] ata5: EH complete
> >> Jul 22 21:23:40 backend3 kernel: ata5.00: configured for UDMA/133
> >> Jul 22 21:23:40 backend3 kernel: ata5.00: device reported invalid CHS sector 0
> >> Jul 22 21:23:40 backend3 kernel: ata5: EH complete
> > 

The above tends to point to a hardware problem with any of the
following.. disk, cable, controller.

My own experience of such messages, they where always caused by
connection problems in the cables with one being "broken" in a similar
way to how a pair of head phones cut out until the cable is "wobbled"
near the jack plug.

Basically a broken wire in the sata cable that works "most of the time"
but under load fails. It was very badly "kinked" near the plug due to
bad case design not allowing much room between the side panel and the
back of the drive and over time and multiple side panel removals moving
the cable to different drives had degraded the integrity.

The second time I had the above was caused by a loose socket on an add
in card (really cheap one), the vibrations from the washing machine spin
dry sequence would cause it to error if under high load (working out
that two unrelated events had to occur at the same time took a while,
especially as the drive in the second sata socket never had any issues);
it was eventually resolved by using a small piece of selotape which
lifted one side of the cable connector causing a tighter fit on the
contact side... a true "bodge-it and scarper" fix that would make an
engineer proud ;-)