[DRBD-user] Drbd hang on write

Claude Pelletier CPelletier at serti.com
Thu Jun 22 21:24:58 CEST 2006

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


Hi All,

I have 2 IBM I series server using Linux

The drbd 0.7.19 version is install on them.
the 2 server are running on a 10mb lines in a wan configuration

The thing I would like to do is explain in detail what's happenning and 
the way I see it. 

1 - all_extents,protocol and snd_buffer parameter have been changed 
2 - Take drbd down and back up on both side( to make sure the changed have 
take effect) 
3 - Start a copy of a 300MB files on the partition /dev/drbd2 
4 - The copy goes all the way 
5 - After about 30 sec to 1 minute when the copy finish we can't have 
access to the /dev/drbd2 partition (true win samba or just doing a ls of 
the partition) 
      all the other drbd partition and the system it self show no 
degradation. 
6 - We see in the cat /proc/drbd the bytes of this partition going from 
primary to secondary 
7 - When the copy is done from primary to secondary the partition 
/dev/drbd2 become back available and performance is 
      back to normal on this partition(no other part of the linux system 
is affect by this) 


So what I see in all this. 

It look like drbd doesn't really do is copy from primary to secondary in 
the background. 
My impression was that drbd would complete is copy in the backround with 
out slowing down the access to the fs on the primary machine. 
I really hope this is not a concept issue. 

If I copy let say a 500MB files the same thing happen except it happen 
even before the copy to the primary finish 
and it can even abort the copy. 

Im really suprise this thing didn't pop up before in drbd forum. 
To me it's basic. 

I really hope there is a parameter somewhere that would fix this. 

The way I see it, it's really a drbd problem cause the system itself still 
response very good. 

It's really the partition that hang until it complete a copy from primary 
to secondary. 

All the other partition under drbd doesn't hang. 

To make all parition hang I would just copy 3 files in each partition and 
I would be able to hang all 
the drbd partition at once. 

They would only get available when the copy from primary to secondary 
complete. 

Can you imagine in a production environment having 10 users copying some 
1G files to the drbd partitions. 

Below is the drbd.conf present on both machine. 


global { 
        minor-count 4; 
        dialog-refresh 600; 
} 
resource drbd0 { 
        protocol A; 
        incon-degr-cmd "/bin/true"; 
        syncer { 
                rate 70M; 
                al-extents 257; 
        } 
        net { 
                sndbuf-size 512k; 

        } 
        on smb-mtl01 { 
                device /dev/drbd0; 
                disk /dev/mapper/VGPrivate_orion-LVPrivate_orion; 
                address 10.10.1.3:7789; 
                meta-disk /dev/sdh1[0]; 
        } 
        on smb-sjo01 { 
                device /dev/drbd0; 
                disk /dev/mapper/VGPrivate_orion-LVPrivate_orion; 
                address 10.10.2.66:7789; 
                meta-disk /dev/sde1[0]; 
        } 
} 
resource drbd1 { 
        protocol A; 
        incon-degr-cmd "/bin/true"; 

        syncer { 
                rate 70M; 
                al-extents 257; 
        } 
        net { 
                sndbuf-size 512k; 

        } 
        on smb-mtl01 { 
                device /dev/drbd1; 
                disk /dev/mapper/VGProfiles_orion-LVProfiles_orion; 
                address 10.10.1.3:7790; 
                meta-disk /dev/sdh1[1]; 
        } 
        on smb-sjo01 { 
                device /dev/drbd1; 
                disk /dev/mapper/VGProfiles_orion-LVProfiles_orion; 
                address 10.10.2.66:7790; 
                meta-disk /dev/sde1[1]; 
        } 
} 
resource drbd2 { 
        protocol A; 
        incon-degr-cmd "/bin/true"; 

        syncer { 
                rate 70M; 
                al-extents 257; 
        } 
        net { 
                sndbuf-size 512k; 

        } 
        on smb-mtl01 { 
                device /dev/drbd2; 
                disk /dev/mapper/VGPublic_orion-LVPublic_orion; 
                address 10.10.1.3:7791; 
                meta-disk /dev/sdh1[2]; 
        } 
        on smb-sjo01 { 
                device /dev/drbd2; 
                disk /dev/mapper/VGPublic_orion-LVPublic_orion; 
                address 10.10.2.66:7791; 
                meta-disk /dev/sde1[2]; 
        } 
} 

Hope we can find a solution to this 

Thanks ! 



Claude Pelletier
Serti Informatique Inc.
Courriel/Email : cpelletier at serti.com
Téléphone/Phone : (514) 493-1909
Télécopieur/Fax : (514) 493-3575
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