Do I need SAS drives?..

[Alan Somers]

On Thu, Aug 10, 2017 at 7:44 AM, Ben RUBSON <ben.rubson at gmail.com> wrote:
>> On 09 Aug 2017, at 17:59, Alan Somers <asomers at freebsd.org> wrote:
>>
>> 3) SAS drives have a lot of fancy features that you may not need or
>> care about.  For example, (...) their error
>> reporting capabilities are more sophisticated than SMART
>
> Really interesting answer Alan, thank  you very much !
> Slightly off-topic but I take this opportunity,
> how do you check SAS drives health ?
> I personally cron a background long test every 2 weeks (using smartmontools).
> I did not experience SAS drive error yet, so not sure how this behaves.
> Does the drive reports to FreeBSD when its read or write error rate cross
> a threshold (so that we can replace it before it fails) ?
> Or perhaps smartd will do ?
>
> As an example below a SAS error counter log returned by smartctl :
>     Errors Corrected by          Total   Correction    Gigabytes    Total
>         ECC         rereads/    errors   algorithm     processed    uncorrected
>     fast | delayed  rewrites  corrected  invocations  [10^9 bytes]  errors
> read:   0       49        0        49     233662     73743.588           0
> write:  0        3        0         3      83996      9118.895           0
> verify: 0        0        0         0      28712         0.000           0
>
> Thank you !
>
> Ben

smartmontools is probably the best way to read SAS error logs.
Interpreting them can be hard, though.  The Backblaze blog is probably
the best place to get current advice.  But the easiest thing to do is
certainly to wait until something fails hard.  With ZFS, you can have
up to 3 drives' worth of redundancy, and hotspares too.

-Alan