Re: [DRBD-user] local disk flush failed with status -95 question

[Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>]

On Thu, Oct 23, 2008 at 02:25:32PM +0200, GAUTIER Hervé wrote:
>
> Hi there !
>
> No information about this DRBD message ?
> Nobody have this log message ?
>
> GAUTIER Hervé a écrit :
>>
>> Hi,
>>
>> I Would like to understand well the following message which appears to  
>> me during a resync:
>> local disk flush failed with status -95
>>
>> errno.h seems to say:
>> #define EOPNOTSUPP      95      /* Operation not supported on  
>> transport endpoint */
>>
>> After some research, I have understood that this is in relation with  
>> "I/O barriers".
>>
>> If I've got this message, there is something (OS, driver, disk, ...)  
>> in my system which does not support "I/O barriers", does it ?

right.
drbd cannot use barriers where it would want to.  so it falls back to
instead "let IO drain and hope for the best".  drbd used to do that
anyways up to 8.0.9 or so, and assumed you have a "safe" device
(no volatile caches involved).

my recommendation:
get a decent raid controller with a battery backed write cache,
switch off all volatile caches in the chain (on the single drives),
and forget about the whole issue.

btw, drbd itself does not yet support barriers for upper layers either.
but we are working on that...

-- 
: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

DRBD® and LINBIT® are registered trademarks of LINBIT, Austria.
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