On Mon, 2013-09-09 at 13:50 +1000, Tudor Holton wrote:

Completely anecdotal evidence, but I was mixing WD Reds and Seagates in 
a QNAP RAID 6 each 3TB for a total of 6TB, and the Seagates kept making 
sounds like they were about to hurl.  Testing each drive individually 
with badblocks and smart came up with all drives OK.  But it kept 
chucking the WDs one by one.  Eventually I removed the Seagates and 
replaced them with WDs and since then no drives have been thrown out.

I can only theorise that there may be a timing issue between WD Reds and 
Seagate.

I wonder if the vibrations of the Seagates was causing the reds to be
thrown?

From what I've read (assuming I understand correctly) they are a low-ish
vibration drive with some fancy head positioning for alignment... but
should be limited to 5 at most, or at least are intended for upto 5
drive systems, so I wonder if this means that more than 5 could suffer
from vibrations throwing disks out?

All that said, I wonder just how sensitive drives are nowadays? While I
have heard of tales of old where someone sneezing in the computer room
would cause large raid clusters to pop I don't know how true they are or
how sensitive drives are to the accumulative vibrations of many disks or
if its more of a case that as the number of disks increases then the
statistical chance of a drive failing increases to the point that it is
more likely to happen in coincidence with an external event, such as a
sneeze.