[DRBD-user] DRBD serious locking due to TOE - UPDATE

Ben Clewett ben at roadrunner.uk.com
Mon Jan 7 09:56:56 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.

Hi Carson,

Thanks for your reply.  It is certainly odd that a write-ahead-cache 
should make DRBD slower rather than faster.

The comments I picked up were from Lars Ellenberg:


"no. more concern about your write cache in the cciss controller,
and whether it lies to the kernel about having written stuff to disk
when in fact it is only in that (probably not battery backed?) write

The fact is that I have a cciss RAID controller with write-ahead-cache. 
  I was experiencing DRBD locking.  Having changed DRBD to use the 
setting in this posting, so far I am not getting locking.

Is this related to my cciss?, or my network cards?, (which were 
certainly contributing), I really don't know :)

But so far my problems are fixed and I don't have any more locking...


Carson Gaspar wrote:
> Ben Clewett wrote:
> ...
>> For those of you having locking and following this thread, I have 
>> found another problem related to our HP Proliant servers.
>> These optionally come with a battery backed up write-ahead-cache on 
>> the cciss controller.  I have 256M of write ahead cache active.
>> I found this thread from Lars suggesting these items may have a 
>> problem where they miss-report storage of data:
>> http://lists.linbit.com/pipermail/drbd-user/2007-June/007033.html
> There is no problem, as long as your write cache is battery backed. If 
> it isn't, you're risking your data. But that isn't your performance 
> problem (it makes things faster, not slower...). It may, however, make 
> your performance uneven. Increasing your buffers allows drbd to queue 
> more data, and smooths out the cciss driver's response time impact.

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