[mythtv-users] How is this pricing possible?

[Raymond Wagner]

On 2/22/2011 23:17, Jay Ashworth wrote:
>> From: "Yan Seiner"<yan at seiner.com>
>> Well, you can take advantage of the fact that myth needs high capacity,
>> low speed. So get a sackful of 1 GB drives and build a few raid-6
>> arrays. I've found that about 3TB is the practical limit of the
>> technology for SATA in terms of verify and rebuild speeds. Maybe the
>> newer controllers are faster, but when time to rebuild starts to
>> exceed 48 hours I get a bit worried.
> Indeed.  I gather RAID-6 avoids the "rebuild time longer than MTBF of drives"
> problem?  :-)

While the UBER (unrecoverable bit error rate) issue is a perfectly valid 
argument, it suffers from lack of any meaningful data.  This issue 
really started getting press about a year and a half ago.  Hard drives 
were advertised with an average rate of less than one UBE per 10^14 
reads, or 12.5TB.  As you started getting into the multi-terabyte 
arrays, the chances of a bit error causing a fault and data loss on a 
rebuild became troublesomely high.

About a year ago, Western Digital started selling consumer drives with 
an advertised average rate of less than one UBE per 10^15 reads.  Now 
you don't just miraculously get an order of magnitude better 
reliability, and presumably WD isn't outright lying.  Presumably, 
manufacturers are just testing that the drives are 'at least this good' 
and leaving it at that.

Is it a future issue people running large arrays need to be aware about? 
Certainly!  Is doom and gloom going to descend upon everyone, and 
destroy their data? No, probably not.