slightly off topic: SMART error values for seagate drives

[Ken Moffat]

On Thu, Jul 02, 2015 at 10:08:16PM -0400, Quartz wrote:
> Is anyone familiar with exactly how the raw_read_error_rate,
> reallocated_sector_count, seek_error_rate, hardware_crc_recovered, and
> udma_crc_error_count values work for seagate drives?
> 
> AFAIK at least some of these fields list the (average?) number of sectors
> between errors, and thus a higher raw value is better ...I think. I have
> several apparently healthy seagate drives with very high rrer/ser/her raw
> values that seem to support this.
> 
> I recently took an older disk out of storage, and as part of my system
> building procedure I always run a few tests over it before putting it back
> into service. Initially it also had high rrer/ser/her raw values. It failed
> a SMART extended test at about 40% remaining with a read failure, and the
> udma_crc_error_count jumped from 0 to 5. I know sometimes this can be just
> transient flakiness, so I just zeroed out the entire drive with dd to
> exercise all the sectors and force any remappings. Now, the
> reallocated_sector_count bumped up to 9, and the raw_read_error_rate and
> hardware_crc_recovered fields plummeted from the millions down to like 13
> ...and have since slowly risen to the 40's.
> 
> I can't tell what's going on with SMART values anymore, every vendor does
> things differently and nothing's ever documented. Is having the reallocated
> sectors value go up still a bad thing, or did seagate change what this
> means? Why did the read error rate and crc recovered fields bottom out, but
> the seek error rate is still in the clouds? Is this drive failing, or fine,
> or what?
> 
Based on a small number of low-end consumer-level desktop machines,
my experience is that an increasing reallocated sector count is a bad
sign.  In theory, we ought to be able to run with a number of
reallocated sectors - but I only really notice when sectors become
(temporarily) inaccessible.  Generally, you get what you pay for -
and the sorts of drives I buy are built down to a price.

ĸen
-- 
This one goes up to eleven!