Re: AHCI timeout when using ZFS + AIO + NCQ

----- Original Message ----- 
From: "Vladislav Prodan" <universite_at_ukr.net>
To: "Steven Hartland" <killing_at_multiplay.co.uk>
Cc: <current_at_freebsd.org>; <fs_at_freebsd.org>
Sent: Sunday, January 27, 2013 3:13 PM
Subject: Re[2]: Re[2]: AHCI timeout when using ZFS + AIO + NCQ


> 
> 
>> ----- Original Message ----- 
>> From: "Vladislav Prodan" <universite_at_ukr.net>
>> 
>> >> Is it always the same disk, of so replace it SMART helps identify issues
>> >> but doesn't tell you 100% there's no problem.
>> > 
>> > 
>> > Now it has fallen off a different HDD - ada0.
>> > I'm 99% sure that MHDD will not find problems in HDD - ada0 and ada2.
>> > I still have three servers with similar chipsets that have similar problems
>> > with blade ahci times out.
>> 
>> I notice your disks are connecting at SATA 3.x, which rings bells. We had
>> a very similar issue on a new Supermicro machine here and after much
>> testing we proved to our satisfaction that the problem was the HW.
> 
> 
> I have a motherboard ASUS M5A97 PRO
> http://www.asus.com/Motherboard/M5A97_PRO/#specifications
> Has replacement SATA data cables.
> Putting hard RAID controller does not guarantee data recovery at his death.

Not sure what that has to do with cable / track lengths via things
like a backplane?

Do you or do you not have a hotswap backplane?

>> Essentially the combination of SATA 3 speeds the midplane / backplane
>> degraded the connection between the MB and HDD enough to cause
>> the disks to randomly drop when under load.
>> 
>> If we connected the disks directly to the MB with SATA cables the
>> problem went away. In the end we had midplanes changed from an
>> AHCI pass-through to active LSI controller.
>> 
>> So if you have any sort of midplane / backplane connecting your disks
>> try connecting them direct to the MB / controller via known SATA 3.x
>> compliant cables and see if that stops the drops.
>> 
>> Another test you can do is to force the disks to connect at SATA 2.x
>> this also fixed it in our case, but wasn't something we wanted to
>> put into production hence the controller swap.
>> 
>> To force SATA 2 speeds you can use the following in /boot/loader.conf
>> where 'X' is disk identifier e.g. for ada0 X = 0:-
>> hint.ahcich.X.sata_rev=2

This is still worth trying as it could still indicate a problem
with your controller, cables or disks.

    Regards
    Steve

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