[Drbd-dev] Handling on-disk caches

Philipp Reisner philipp.reisner at linbit.com
Mon Nov 12 17:24:12 CET 2007

On Monday 12 November 2007 16:59:24 Graham, Simon wrote:
> > For item 3 I have an other opinion.
> >
> > On the primary we have a data structure called the "transfer log" or
> tl
> > in the code. Up to now this was mainly important for protocol A and B.
> >
> > It is a data structure conaining objects for all our self-generated
> > drbd-barriers on the fly, and objects for all write requests between
> > these barriers.
> >
> > If we loose connection in protocol A or B we need to mark everything
> > we find in the transfer_log as out-of-sync in the bitmap.
> >
> > When we also do this for protocol C, _AND_ use BIO_RW_BARRIER for
> > doing writing on the secondary we have solved the issue you
> > described in the first part of the mail.
> I like it! MUCH better than marking the GB's of data covered by the
> AL...
> I presume you will work on this as part of 8.2 rather than as a fix to
> 8.0? Since I am currently locked on 8.0, I will probably look at
> implementing your suggestions as updates to 8.0 and submit them for
> consideration in 8.2.

Right, I thought about this, and forgot to mention it in the mail.

From a technical point of view it is possible to do the BIO_RW_BARRIER
stuff in DRBD-8.0 since it can be done without changing the protocol.

From the point of view as release manager I get bellyache when considering
such a big change for DRBD-8.0.

Please start the work based on the 8.0 tree, I postpone the
decision if it should go into 8.2 only or into 8.0 (and propagated to 
8.2 of course as well) until we see the intrusiveness of the patch.

Moving patches between 8.0 and 8.2 is still quite possible... 

: Dipl-Ing Philipp Reisner                      Tel +43-1-8178292-50 :
: LINBIT Information Technologies GmbH          Fax +43-1-8178292-82 :
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