[DRBD-user] Speed Sync seems to be limited on gigabit ethernet

Marcello Lupo mlist at itspecialist.it
Wed Jun 20 16:51:30 CEST 2007

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

thanks for answers.
Comments inline

Siim Vahtre wrote:
> On Wed, 20 Jun 2007, Marcello Lupo wrote:
>> If i force the sync of the partitions to drbd with invalidate_remote 
>> it do not go over 12 Mb/sec.
> This doesn't seem normal.
> Some obligatory questions:
> * Are you sure you actually have working fullduplex Gbit link? (check 
> with ethtool)
Settings for eth1:
        Supported ports: [ MII ]
        Supported link modes:   10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Half 1000baseT/Full
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full
                                100baseT/Half 100baseT/Full
                                1000baseT/Half 1000baseT/Full
        Advertised auto-negotiation: Yes
        Speed: 1000Mb/s
        Duplex: Full
        Port: Twisted Pair
        PHYAD: 1
        Transceiver: internal
        Auto-negotiation: on
        Supports Wake-on: g
        Wake-on: d
        Current message level: 0x000000ff (255)
        Link detected: yes

> * Are you sure you actually can write to your disks faster than 
> 12Mbytes/sec? (try with benchmarking tool that comes with drbd 'dm.c')
I tried to copy with scp from one machine to the other a 4GB file and it 
went at ~40Mb/s.

Tool you said dm.c the documentation says that is untouched from version 
0.6 and not working currently with 0.7 version.
SOme times in cat /proc/drbd i see some peak of speed around 18/20 
Mb/sec but it is very rare. the average is everytime around 14/15 Mb/sec.

Now i tried with bonnie++ and this is the result

Version  @version@      ------Sequential Output------ --Sequential 
Input- --Random-
                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- 
Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  
/sec %CP
host0            4G 40987  99 85422  33 45074  11 53951  99 120726  15 
1152.6   2
host0            4G 41007  99 88090  34 44630  11 53664  99 122682  16 
1169.1   1
                    ------Sequential Create------ --------Random 
                    -Create-- --Read--- -Delete-- -Create-- --Read--- 
files:max:min        /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  
/sec %CP
host0            16 17641  99 +++++ +++ 16958  99 19706 100 +++++ +++ 
16110  99
host0            16 15767  76 +++++ +++ 17099  99 19778  99 +++++ +++ 
16256  10

> * Are you sure nothing else is writing to disks at the same time?
Yes the servers are not used at the moment. I'm just making all 
preinstall tests of speed and so on before install.

>> i tried with rate option to 50M,40M,30M and it is the same.
> * Did you drbdadm adjust after changing config?
I made drbd completely stop and start to be sure all the times i changed 
the config.

> * Have you searched the mailing-list archives? I think I have seen 
> several questions like yours, maybe someone has already solved problem 
> like this.

I searched for something but found nothing that was usefull to me.. May 
be i didn't searched so well.


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