[DRBD-user] Syncer's "after" dependency for online verifying

Dan Barker dbarker at visioncomm.net
Mon Jun 4 23:27:38 CEST 2012

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


> Is it possible to have DRBD verify B only when A is done verifying?

I use crontab.

On Monday at 2:11 AM, verify r0 
On Tuesday at 2:11 AM, verify r1
On Wednesday at 2:11 AM, verify r2 
On Thursday at 2:11 AM, verify r3

  --or--

11  2  *   *   1     /sbin/drbdadm verify r0
11  2  *   *   2     /sbin/drbdadm verify r1
11  2  *   *   3     /sbin/drbdadm verify r2
11  2  *   *   4     /sbin/drbdadm verfiy r3

Dan


-----Original Message-----
From: drbd-user-bounces at lists.linbit.com
[mailto:drbd-user-bounces at lists.linbit.com] On Behalf Of Lars Ellenberg
Sent: Friday, June 01, 2012 11:50 AM
To: drbd-user at lists.linbit.com
Subject: Re: [DRBD-user] Syncer's "after" dependency for online verifying

On Fri, Jun 01, 2012 at 12:03:20PM +0200, Lionel Sausin wrote:
> Dear DRBD community,
> 
> We're using DRBD 8.3.11 with 2 resources called A and B.
> B is configured to sync after A, but when I run "drbdadm verify all"
> both resources start verifying immediately.

That is intentional.

In error scenarios, you do not have much control over when a network
fails/recovers, or a node reboots.
So there we have dependencies to not overload the system with too much
parallel resync activity.

For verify, that is entirely triggered from userspace, you have full
controll.

> Is it possible to have DRBD verify B only when A is done verifying?

Sure.
Just don't start the verify on B while the verify on A is still running.

 ;-)

like,
 for minor in 0 1 2 ; do
 	drbdsetup $minor verify ; drbdsetup $minor wait-sync  done

Or similar.

> If not, has it been/will it be possible in versions after 8.3.11?

I don't see any kernel support for "verify dependencies" coming soon, as you
can easily serialize verify operations in userland.


Besides,
now that we have the dynamically adaptive resync rate controller, and it is
used for verify as well, for most cases I'd recommend to enable it globally,
and get rid of the resync dependencies.

--
: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com
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