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

GAUTIER Hervé herve.gautier at thalesgroup.com
Mon Oct 27 14:22:23 CET 2008

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

Lars Ellenberg a écrit :
>> 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...

Thank you very much for the explanation and advices.
How could I know from where comes the barrier problem ?

I have identified the following different level of the chain that may be 
- OS: I am currently running on Red Hat Enterprise Linux ES release 4 
(Nahant Update 6) kernel 2.6.9-67.ELsmp. Is there a minimum required 
kernel version for the barriers implementation ?
- DRBD: The current version I am using is drbd-8.2.5.
- Drivers: I currently use disks connected on a HP Smart Array 642 
Controller using the cciss driver 2.6.16 provided by the Red Hat 
Enterprise Linux ES release 4 (Nahant Update 6). I haven't seen any 
option on this driver.
- Controller: I will check in there is any cache option in the HP Smart 
Array 642 Controller firmware.
- Disks: I will try to find any information on the disks used in order 
to check if the used some cache.

Anything else I have forgotten ?

Thank in advance,

Best regards.


More information about the drbd-user mailing list