[DRBD-user] very slow io with drbd and nfs

Fatih fatih at kamilkoc.com.tr
Mon Jan 25 10:12:11 CET 2010


Hi
here is the structure

NFSCLIENT------------(NFSSERVER)  drbd  node1 active
                                |
                            (NFSSERVER  )  drbd node2 passive

case 1. if i copy 63M file (which is on nfs server) from nfs client it tooks 
approximately 55 seconds which is 1.2 MB in second very slow
(root at nfsclient:/# time cp /nfsmount/file_name /nfsmount/tmp_file)

case 2. disconnecting  drbd  connection with "drbdadm disconnect 
resource_name" on node 2 after that

 if i copy 63M file (which is on nfs server) from nfs client it tooks 
approximately 5 seconds which is 12 MB in second which is normal and means nfs 
client,  server and network connection has no problem
(root at nfsclient:/# time cp /nfsmount/file_name /nfsmount/tmp_file2)


case 3. connecting drbd source again with  drbd connect resource_name on node 
2 and waiting for both nodes became uptodate
after that

if i copy file from drbd block device to drbd block device on nfs server, 
completed with 25 MB / second which is normal and means drbd has no problem
(root at nfsserver:/# time cp /drbdmountpint/file_name /drbdmountpoint/tmp_file)

as you can see i am very confused and have no idea where is the problem

any suggestions

both nfs server node1 and node2 has centos 5.4 32 bit drbd version 8.0.16 
which is in default yum repository

all networks are gbit.  Nfs network and drbd NETWORKS ARE SEPARATED between 
each other with separated gbit nics. there is no router or any other active 
network device, they are connected with crossover cable
and last i used protocol B and C also.
-------------------------------------------
dbrbd configuration file is below

global { usage-count no; }
resource repdata {
  protocol A;
  startup {
  wfc-timeout 0; degr-wfc-timeout     120;
  }
  disk {
  on-io-error detach;
  }
  net {
  }
  syncer {
  rate 80M;
  }
  on node1.kkoc.com.tr {
    device /dev/drbd0;
    disk /dev/sda1;
    address 172.16.0.1:7788;
    meta-disk internal;
  }
  on node2.kkoc.com.tr {
    device /dev/drbd0;
    disk /dev/md0;
    address 172.16.0.2:7788;
    meta-disk internal;
  }
}

-------------------------------------------

thanks for your replies
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