Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
----- Original Message ----- > From: "Lars Ellenberg" <lars.ellenberg at linbit.com> > To: drbd-user at lists.linbit.com > Sent: Thursday, February 2, 2012 10:37:31 AM > Subject: Re: [DRBD-user] Confused about no-disk-drain > > On Thu, Feb 02, 2012 at 10:27:05AM -0500, Jake Smith wrote: > > Lars, > > > > I didn't want to hijack a different thread so I started a new one. > > I > > want to understand better why you said in another thread today not > > to > > use no-disk-drain (quote): > > > > > Will people please STOP using no-disk-drain. On most hardware, > > > it does > > > not provide measurable performance gain, but may risk data > > > integrity > > > because of potential violation of write-after-write dependencies! > > > > I also found you said in another older thread: > > > > >Do not use "no-disk-drain", unless you are absolutely sure that > > >nothing > > >in the IO stack below DRBD could possibly reorder writes. > > > > Unfortunately I'm not that knowledgeable on storage so this may be > > a ignorant question but... > > > > In the man page for drbd.conf (version 8.3.7) it states using none > > is > > the best performance choice if using a storage device with BBWC. > > Which it is. But as you are not the only one confused about this, > we felt the need to clarify and improve the man page, see there: > > http://git.drbd.org/gitweb.cgi?p=drbd-8.3.git;a=commitdiff;h=f952dcfe > > .-- Commit message: > | doc: clearly document no-disk-drain as DONT USE > | > | When used carelessly, because it is documented as the method to get > | "best performance" (which it is, but only if used on a suitable IO > | stack), it can theoretically cause write-reordering (potential data > | corruption), and will disturb the drbd protocol causing spurious > | disconnect/reconnect cycles, like: > | > | block drbd0: BAD! BarrierAck #822515458 received, expected > | #822515457! > | block drbd0: peer( Secondary -> Unknown ) conn( Connected -> > | ProtocolError ) pdsk( UpToDate -> DUnknown ) > | > | There are very few cases where using that option is "legal", > | and even then the performance increase is marginal. > | > | Document as DONT USE. > '-- > > Actual diff (and new man page text) see url above. Well I may not understand *why* much better but that's OK because I can follow directions so Do Not Use works for me! :-) Will both 8.3 and 8.4 users guides be updated to reflect these changes at some point? Thanks! Jake > > -- > : Lars Ellenberg > : LINBIT | Your Way to High Availability > : DRBD/HA support and consulting http://www.linbit.com > _______________________________________________ > drbd-user mailing list > drbd-user at lists.linbit.com > http://lists.linbit.com/mailman/listinfo/drbd-user > >