[DRBD-user] [Fwd: Re: [Linux-HA] heartbeat 2.0.8: lockups] kerneloops

Ross S. W. Walker rwalker at medallion.com
Thu Feb 22 00:48:59 CET 2007

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.




More information about the drbd-user mailing list