Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.
I solved this problem. It turns out it wasn't drbd at all in this case. The ethernet drivers on the clients doing the benchmarking were, for a lack of a better term, wacky. I upgraded the drivers and I am getting consistently better results now. I have discovered a separate-but-related problem though with a different back-end io driver for iSCSI that attempts to do direct synchronous io to the drbd device. When using this back-end module to directly access an LVM/MD/SD device the throughput is fine, but when run on drbd the performance is horrible. I posted a separate post under "DRBD and Direct Block IO" to the list and included the source code of the back-end module that does the block io. Maybe there is something in the way it does the io that is incompatible with DRBD. -Ross > -----Original Message----- > From: drbd-user-bounces at lists.linbit.com > [mailto:drbd-user-bounces at lists.linbit.com] On Behalf Of > Leroy van Logchem > Sent: Thursday, January 04, 2007 3:58 AM > To: drbd-user at lists.linbit.com > Subject: Re: [DRBD-user] Large block IO bottleneck > > > >>>> Hi there I am using DRBD 0.7.21 with iSCSI Enterprise > >>>> > > The 32k are a rather arbitrary value we have chosen in > DRBD. Such a limit > > is needed for some of the algorithms in the area of the two primary > > nodes, write conflict detection code. > > > > If you really want you can change that define (HT_SHIFT), > but probably > > the positive effects are out-numbered by negative effects > (more collision > > in hash tables etc...) > > > I was hoping to analyse the difference by patching the source but the > HT_SHIFT define > is only used in the 8.x code. What would need changing to try > 32K BIO's > in the 0.7.x code? > _______________________________________________ > drbd-user mailing list > drbd-user at lists.linbit.com > http://lists.linbit.com/mailman/listinfo/drbd-user > ______________________________________________________________________ This e-mail, and any attachments thereto, is intended only for use by the addressee(s) named herein and may contain legally privileged and/or confidential information. If you are not the intended recipient of this e-mail, you are hereby notified that any dissemination, distribution or copying of this e-mail, and any attachments thereto, is strictly prohibited. If you have received this e-mail in error, please immediately notify the sender and permanently delete the original and any copy or printout thereof.