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RE: [Xen-users] Re: Xen, LVM, DRBD, Linux-HA

To: "Steve Wray" <steve.wray@xxxxxxxxx>, <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-users] Re: Xen, LVM, DRBD, Linux-HA
From: "Ross S. W. Walker" <rwalker@xxxxxxxxxxxxx>
Date: Tue, 22 Apr 2008 16:27:49 -0400
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Thread-topic: [Xen-users] Re: Xen, LVM, DRBD, Linux-HA
Please do not hijack threads, please put all your drbd questions
to the drbd-user list.

If properly setup and maintained drbd should work properly.


> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Steve Wray
> Sent: Tuesday, April 22, 2008 4:19 PM
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-users] Re: Xen, LVM, DRBD, Linux-HA
> I am going to reply to this thread but I'm going to start 
> from something 
> new as it doesn't seem to be covered in this thread so far.
> I have been testing drbd under Xen and found some very 
> disturbing things.
> I'd like to implement this in a production system but this scares the 
> hell out of me...
> I have two Dom0 servers connected with a crossover cable between two 
> gigabit e1000 NICs. No switch involved.
> One DomU on each server with a 20G drbd device shared between them.
> The drbd config contains:
>    syncer {
>      rate 10M;
>      group 1;
>      al-extents 257;
>    }
>    net {
>      on-disconnect reconnect;
>    }
> so the net section is working at defaults. At first I had 
> thought that 
> the problems I was seeing was due to timeout values etc and tried 
> various parameters in the net section but nothing made any difference.
> When, on the current secondary node, I execute
> drbdadm invalidate all
> I get frequent errors such as:
> drbd0: PingAck did not arrive in time.
> drbd0: drbd0_asender [1572]: cstate SyncSource --> NetworkFailure
> drbd0: asender terminated
> drbd0: drbd_send_block() failed
> drbd0: drbd0_receiver [1562]: cstate NetworkFailure --> BrokenPipe
> drbd0: short read expecting header on sock: r=-512
> drbd0: worker terminated
> drbd0: ASSERT( mdev->ee_in_use == 0 ) in 
> /usr/src/modules/drbd/drbd/drbd_receiver.c:1880
> drbd0: drbd0_receiver [1562]: cstate BrokenPipe --> Unconnected
> drbd0: Connection lost.
> I observe the xm top in both Dom0's and I note a HUGE amount 
> of dropped 
> RX packets being reported on both DomU's vif interfaces. The 
> dropping of 
> RX packets is continuous throughout the drbd resync and grows 
> extremely 
> large.
> The ifconfig output within the DomU's do not show any dropped packets.
> I have used iperf to test the performance of the crossover 
> link and it 
> is fine when there is no drbd syncing going on.
> I have tried various things such as setting sysctl.conf options:
> net.core.rmem_default=65536
> net.core.wmem_default=65536
> net.core.rmem_max=16777216
> net.core.wmem_max=16777216
> net.ipv4.tcp_rmem = 4096 87380 16777216
> net.ipv4.tcp_wmem = 4096 65536 16777216
> but so far the only thing that prevents the "PingAck did not 
> arrive in 
> time" errors is to take the sync rate down to 1M.
> My Xen version info is:
> Xen version 3.0.3-1 (Debian 3.0.3-0-4)
> Please advise...
> Thanks!
> _______________________________________________
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> http://lists.xensource.com/xen-users

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