Re: Recent drive errors

[Thomas Fjellstrom <thomas@fjellstrom.ca>]

On Tue 19 May 2015 08:34:55 AM Phil Turmel wrote:
> Hi Thomas,
> 
> On 05/19/2015 07:08 AM, Thomas Fjellstrom wrote:
> > Hi,
> > 
> > I have this one drive that dropped out of one of my arrays once. It shows
> > UNC errors in SMART (log appended), and Reported_Uncorrect is 5. There
> > are no smart test failures or any other SMART values that look
> > spectacularly wrong, other than maybe Load_Cycle_Count which is 10625
> > (these seagates used to constantly park and unpark before i updated the
> > firmware).
> > 
> > I'm wondering whether or not this drive is still safe to use. I feel like
> > I
> > can't trust it, especially after all the other Seagates I had that failed
> > in the past few years. I'm running a tool called whdd on it right now and
> > it shows very consistent latency spikes above 150ms. Really, I'm
> > wondering if this drive is RMAable as is, or if i have to wait for it to
> > degrade further as i have another drive with like 10k reallocated sectors
> > to send in. I have already replaced both with WD Red's so I can do
> > whatever tests are needed to figure it out.
> 
> Based on the smart report, this drive is perfectly healthy.  A small
> number of uncorrectable read errors is normal in the life of any drive.

Is it perfectly normal for the same sector to be reported uncorrectable 5 
times in a row like it did?

How many UREs are considered "ok"? Tens, hundreds, thousands, tens of 
thousands?

These drives have been barely used. Most of their life, they were either off, 
or not actually being used. (it took a while to collect enough 3TB drives, and 
then find time to build the array, and set it up as a regular backup of my 
11TB nas).

>  It has no relocations, and no pending sectors.  The latency spikes are
> likely due to slow degradation of some sectors that the drive is having
> to internally retry to read successfully.  Again, normal.

The latency spikes are /very/ regular and theres quite a lot of them.
See: http://i.imgur.com/QjTl6o3.png

> I own some "DM001" drives -- they are unsuited to raid duty as they
> don't support ERC.  So, out of the box, they are time bombs for any
> array you put them in.  That's almost certainly why they were ejected
> from your array.
>
> If you absolutely must use them, you *must* set the *driver* timeout to
> 120 seconds or more.

I've been planning on looking into the ERC stuff. I now actually have some 
drives that do support ERC, so it'll be interesting to make sure everything is 
set up properly.

> HTH,

Thank you :)

> Phil
> 
> http://marc.info/?l=linux-raid&m=133761065622164&w=2
> http://marc.info/?l=linux-raid&m=135811522817345&w=1
> http://marc.info/?l=linux-raid&m=133761065622164&w=2
> http://marc.info/?l=linux-raid&m=133665797115876&w=2
> 
> 
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-- 
Thomas Fjellstrom
thomas@fjellstrom.ca