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: Gerry Reno [mailto:greno at verizon.net] > Sent: Wednesday, February 21, 2007 5:29 PM > To: Ross S. W. Walker > Cc: drbd-user at lists.linbit.com > Subject: Re: [DRBD-user] [Fwd: Re: [Linux-HA] heartbeat > 2.0.8: lockups] kerneloops > > Ross S. W. Walker wrote: > > There is a known bug in the current implementation of MD raid, > > specifically for raid-1 based arrays. The current MD code fails to > > preserve the BIO_RW_BARRIER flag on cloned bios. > > > > What this translates to in DRBD is severe performance penalties and > > possible meta-data integrity issues for meta-data stored on > MD raid-1 > > volumes. > > > > Please use an alternate location for your meta-data then an > MD RAID-1. I > > recommend hardware raid, or LVM-mirror, or standalone disk. > > > > -Ross > > > > > Do you think this would result in the lockups I'm seeing? I haven't > noticed any performance issues. Resyncs proceed at about > 12MB/s which is > about all you can get out of gigabit (not) networking. Re-syncs over gigabit should perform much faster, normal disk i/o should be about twice as fast. > Are there any patches for the md flag issue? I can move the > metadata if > necessary but a patch to fix the problem would be ok too. > I'll probably > just move it to the root disk. Although, now that I'm looking root > directory is on a RAID-1 array also. In fact, the whole machine is > RAID-1 arrays including /boot! Now what do I do? If you google drbd raid1 meta-data, you should find the md patch Lars submitted in December. You could get kernel source, apply the patch and make a custom kernel. I cannot say either way, but there is a significant performance penalty. Would that cause a panic, maybe not, it is definitely a problem area that should be avoided. -Ross ______________________________________________________________________ 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.