[DRBD-user] 3 node chain config

paziulek paziu at yahoo.com
Wed Nov 4 14:27:52 CET 2009


Thank you,

Great information,
Unfortunately the ancient kernel I am running, and will be running for a
while,
Does not compile 8.3.x code,
Some of the required kernel features do not exist in 2.4,

Mounting of a secondary, in a non production environment,
and expecting data mismatches, gave me better results that I expected,
At one point I might abandon this idea,
But so far it does whatever I need....

Thanks a lot,

Mike Fiedler






Ehud Karni wrote:
> 
> On Tue, 3 Nov 2009 11:57:10 paziulek wrote:
>>
>> I would like to create 2 copies of the primary in a "chain"
>> configuration:
>> ( sys1 mirror to sys2, sys2 mirror to sys3 - [same data on all] )
>>
>> sys1/sda10 -> sys2/sda10 -> sys3sda10
> 
> Below is my configuration that does exactly that.
> 
>> Q1: is there a way of mirroring the secondary?
>> Q2: is there a way of mirroring primary to 2 secondaries? ( I am using
>> drbd
>> 0.7.5 on a 2.4.21 system )
> 
> Q1 - yes, see my configuration.
> 
> Q2 - AFAIK yes, with stacked primary (what I do on the secondary).
> 
> Also, I think it works on DRBD 8.3.x only (not on 7.x.x).
> 
>> and if somebody would ask why I would need such config:
>> I want to mount the sdaX filesystem on sys3 in read-only mode to have
>> access
>> to semi-real-time data and at the same time have full mirror on sys2 with
>> no
>> sdaX access other than DRBD.
> 
> As far as my understanding of DRBD goes, you can not do that.
> You can NOT mount (even read only) an updating secondary.
> 
> Ehud.
> 
> 
> -------------------- /etc/drbd.conf --------------------
> ##  lcl-nfs  -->  bu-lcl  -->  bu-rmt
> 
> common {
>   protocol A;
> 
>   startup {
>     wfc-timeout  60;
>   }
> 
>   disk {
>       on-io-error  pass_on ;
>       no-disk-barrier ;
>       no-disk-flushes ;
>       # no-md-flushes;
>       no-disk-drain ;
>   }
> 
>   net {
>     # this is the size of the tcp socket send buffer increase it
> _carefully_ !!
>     sndbuf-size 0;
>     rcvbuf-size 0;
> 
>     # timeout       60;    #  6 seconds  (unit = 0.1 seconds)
>     # connect-int   10;    # 10 seconds  (unit = 1 second)
>     # ping-int      10;    # 10 seconds  (unit = 1 second)
>     # ping-timeout   5;    # 500 ms (unit = 0.1 seconds)
> 
>     max-buffers     8192;
>     unplug-watermark   8192;
> 
>     # The highest number of data blocks between two write barriers.
>     max-epoch-size     8192;
> 
>     data-integrity-alg "md5";
> 
>   }
> 
>   # rate is given in units of _byte_ not bit
>   syncer {
>     verify-alg md5 ;
> 
>     # Configures the size of the active set. Each extent is 4M,
>     # 257 Extents ~> 1GB active set size.
>     # BTW, the hash algorithm works best if the number of al-extents is
> prime.
>     al-extents  499;
> 
>   }
> 
> }
> 
> resource rmt {
>   disk {
>     ## stack size 1459913168 K
>     ##  meta size     262144 K (256 MB)
>              size 1460175312K;
>            no-md-flushes ;
>   }
> 
>   startup {
>     become-primary-on bu-lcl ;
>   }
> 
>   # rate is given in units of _byte_ not bit
>   # slow line to Med1 - Max of 6MB
>   syncer {
>     rate 4M ;
>   }
> 
>   on bu-lcl {
>     device     /dev/drbd0;
>     disk       /dev/sdb1;
>     address    192.168.0.84:7789;
>     meta-disk  /dev/sda4[1];
>   }
> 
>   on bu-rmt {
>     device     /dev/drbd0;
>     disk       /dev/md_d0p1;
>     address    192.168.1.87:7788;
>     meta-disk  /dev/cciss/c0d0p3[0];
>   }
> 
> }
> 
> 
> resource lcl {
>   disk {
>     size 1459913168K;
>   }
> 
>   startup {
>     become-primary-on  lcl-nfs ;
>   }
> 
>   # rate is given in units of _byte_ not bit
>   syncer {
>     rate 30M ;
>   }
> 
>   on lcl-nfs {
>     device     /dev/drbd0;
>     disk       /dev/sdb;
>     address    192.168.239.1:7789;
>     meta-disk  internal;
>   }
> 
>   stacked-on-top-of rmt {
>     device     /dev/drbd1;
>     address    192.168.239.2:7788;
>   }
> 
> }
> 
> 
> 
> 
> --
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