[DRBD-user] I/O barrier problem

GAUTIER Hervé herve.gautier at thalesgroup.com
Tue Nov 4 10:11:09 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.

Hello Peter !

Thank you for your precious answer !
I will see what I could get from HP on this point.

Again, many thanks.

Petrakis, Peter a écrit :
> Hello Hervé,
> The cciss driver doesn't support i/o barriers, however, if you have a BBWC
> (battery backed write cache) you should be fine. I recently explored the
> possibility of adding barriers though the available specs don't confirm
> whether SYNCHRONIZE CACHE is supported, they do however support the ability
> to flush the entire cache, which would kill performance. I've been in contact with HP in search of a definitive answer and what I got was "there's a new spec coming out" and they don't know when it'll be ready.
> I agree that there ought to be a way to flush the cache to the physical disks associated with a single logical volume but until there's a definitive answer, any i/o barrier implementation would essentially be unpredictable.
> Feel free to ask HP regarding this issue :)
> Peter
> P.S. http://cciss.sourceforge.net
>> -----Original Message-----
>> From: drbd-user-bounces at linbit.com [mailto:drbd-user-bounces at linbit.com]
>> On Behalf Of GAUTIER Hervé
>> Sent: Monday, November 03, 2008 8:12 AM
>> To: drbd-user at linbit.com
>> Subject: [DRBD-user] I/O barrier problem
>> Hi there !
>> I need some more explanations in order to know from where comes a
>> barrier problem (message local disk flush failed with status -95).
>> I have identified the following different levels of the chain that may
>> be involved:
>> - 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.
>> --
>> Hervé GAUTIER
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