[OmniOS-discuss] How bad are these controller / io errors??

[Garrett D'Amore]

SATA drives behind SAS expanders have a pathological error case.  If a drive encounters errors and it needs to be reset then the entire set of drives will take the reset.  If any io is in flight this will error as a result often causing another reset.  The result can best be described as a cascade failure. 

There may be things software can do to mitigate this but experience is that it doesn't. 

So just because the array is working fine now does not mean that it won't fail tragically when the first problems occur.   

I have personal experience with this failure mode.

As a result I strongly discourage the use of SATA drives unless they are directly connected to the hba without any expanders or port multipliers. 

You ignore this advice at your own risk.  Don't penny pinch on the drives   It ALWAYS costs you in the long run. 

Sent from my iPhone

On Aug 19, 2013, at 4:25 PM, steve at linuxsuite.org wrote:

>> Can't agree more here. Desktop firmwares are designed to try harder to
>> never return an error.  While this is what home users want, it's an
>> anathema to large configurations with redundancy where you would prefer to
>> just get the error so you can handle it - usually by doing the op on
>> another drive.
>> 
>> Use enterprise drives if you love your data and your ability to access it.
> 
>        Yes I know, I know....  Desktop hardware sucks. Didn't know there was
> Enterprise (ie none Desktop) SATA. Perhaps the solution is to  partition
> the data and do "deep" storage that never gets read on large bulk SATA and
> then have a smaller SAS pool for the often read/written stuff.
> 
>      Anyway, large storage rollouts will always be looking for
> the cheapest solution. Even if it isn't perfect. I do backups
> to a SATA pool (behind SAS expanders) with zfs send,.. no problems errors
> whatever YET!!
> (cross fingers)
> 
>       -steve
> 
>> 
>> Sent from my iPhone
>> 
>> On Aug 19, 2013, at 2:47 PM, Eric Sproul <esproul at omniti.com> wrote:
>> 
>>> On Mon, Aug 19, 2013 at 5:35 PM,  <steve at linuxsuite.org> wrote:
>>>>    4T SATA  here
>>>> 
>>>> http://www.newegg.com/Product/Product.aspx?Item=N82E16822178338
>>>> 
>>>>         are $179
>>> 
>>> That's a desktop drive, not nearline enterprise, so it's
>>> apples-oranges.  You get what you pay for.  Desktop drives can take
>>> much, much longer to respond to commands, leading the HBA/expander to
>>> declare them dead and reset them, and the rest is history.
>>> 
>>> Avoid desktop parts.  :)
>>> 
>>> Eric
>>> _______________________________________________
>>> OmniOS-discuss mailing list
>>> OmniOS-discuss at lists.omniti.com
>>> http://lists.omniti.com/mailman/listinfo/omnios-discuss
> 
> _______________________________________________
> OmniOS-discuss mailing list
> OmniOS-discuss at lists.omniti.com
> http://lists.omniti.com/mailman/listinfo/omnios-discuss