Provided by: drbd0.7-utils_0.7.25-1.1_i386 bug


       drbd.conf - Configuration file for DRBD’s devices


       The    file    /etc/drbd.conf   is   read   by   /etc/init.d/drbd   and
       /etc/ha.d/resource.d/drbddisk  which   are   included   in   the   DRBD

       The file format was designed as to allow to have a verbatim copy of the
       file on both nodes of the cluster.  It is highly recommended to  do  so
       in order to keep your configuration manageable. The file /etc/drbd.conf
       should  be  the  same  on  both   nodes  of  the  cluster.  Changes  to
       /etc/drbd.conf do not apply immediately.

       resource drbd0 {
         protocol C;
         incon-degr-cmd "halt -f";

         on thost1 {
           device    /dev/drbd1;
           disk      /dev/hda7;
           meta-disk  internal;

         on thost2 {
           device    /dev/drbd1;
           disk      /dev/hda7;
           meta-disk  internal;
       In  this  example  there is a single DRBD resource (called drbd0) which
       uses protocol C for the connection between  its  devices.   The  device
       which   runs  on  host  thost1  uses  /dev/drbd1  as  devices  for  its
       application, and /dev/hda7 as low level storage for the data.   The  IP
       addresses are used to specify the networking interfaces to use.

       There  may  be  multiple  resource sections in a single drbd.conf file.
       For more examples please have a  look  at  the  DRBD  Quickstart  Guide


       The  file consists of sections and parameters.  A section begins with a
       keyword, sometimes an additional name, and an opening brace (‘‘{’’).  A
       section  ends  with  a  closing  brace  (‘‘}’’.  The braces enclose the

       section [name] { parameter value; [...] }

       A parameter starts with the identifier of  the  parameter  followed  by
       whitespace.  Every  subsequent  character  is considered as part of the
       parameters value. A special case  are  Boolean  parameters  which  only
       consist  of  the  identifier.  Parameters are terminated by a semicolon

       Some parameter values have default units which might be overruled by K,
       M  or G. These units are defined in the usual way (K = 2^10 = 1024, M =
       1024 K, G = 1024 M).

       Comments may be placed into the configuration file and must begin  with
       a hash sign (‘‘#’’). Subsequent characters are ignored until the end of
       the line.

       skip   Comments out chunks of text, even spanning more than  one  line.
              Characters  between  the  keyword  skip  and  the  opening brace
              (‘‘{’’)are  ignored.  Everything  enclosed  by  the  braces   is
              skipped.   This  comes in handy, if you just want to comment out
              some ’resource [name]  {...}’  section:  just  precede  it  with

       global Configures  some  global parameters. Currently only minor-count,
              dialog-refresh and disable-ip-verification are allowed here. You
              may  only  have  one  global  section,  preferably  as the first

       resource name
              Configures a DRBD resource.  Each resource section needs to have
              two on host sections and may have a startup, a syncer, a net and
              a disk section.  Required parameter in this  section:  protocol.
              Optional parameter: incon-degr-cmd.

       on host-name
              Carries the necessary configuration parameters for a DRBD device
              of the enclosing resource.   host-name  is  mandatory  and  must
              match  the  linux  hostname  (uname  -n)  of  one  of the nodes.
              Required parameters in  this  section:  device,  disk,  address,

       disk   This  section  is used to fine tune DRBD’s properties in respect
              to the low level  storage.  Please  refer  to  drbdsetup(8)  for
              detailed description of the parameters.  Optional parameter: on-
              io-error, size.

       net    This section is used to  fine  tune  DRBD’s  properties.  Please
              refer to drbdsetup(8) for detailed description of this section’s
              parameters.  Optional parameters: sndbuf-size, timeout, connect-
              int,  ping-int,  max-buffers,  max-epoch-size, unplug-watermark,
              ko-count, on-disconnect.

              This section is used to  fine  tune  DRBD’s  properties.  Please
              refer to drbdsetup(8) for detailed description of this section’s
              parameters.  Optional parameters: wfc-timeout, degr-wfc-timeout.

       syncer This section is used to fine tune the synchronisation daemon for
              the  device.  Please  refer   to   drbdsetup(8)   for   detailed
              description  of this section’s parameters.  Optional parameters:
              rate, group, al-extents.

       minor-count count
              count may be a number from 1 to 255.

              Use minor-count if you  want  to  define  more  resources  later
              without reloading the DRBD kernel module. Per default the module
              loads with exactly as many devices as configured in  this  file.
              Built-in  default  for module is 2, and 8 for monolithic kernel.
              For monolithic kernel minor-count is ignored, and  you  have  to
              pass  a  kernel  boot parameter drbd.minor_count=count to change
              the default.

       dialog-refresh time
              time may be 0 or a positive number.

              The user dialog redraws the second count every time seconds  (or
              does no redraws if time is zero). The default is 1.

              Use   disable-ip-verification  if,  for  some  obscure  reasons,
              drbdadm can/might not use ip or ifconfig to do  a  sanity  check
              for the IP address, you can disable it with this this option.

       protocol prot-id
              On  the  TCP/IP  link  the  specified  protocol  is  used. Valid
              protocol specifiers are A, B, and C.

              Protocol A: write IO is reported as completed, if it has reached
              local disk and local TCP send buffer.

              Protocol B: write IO is reported as completed, if it has reached
              local disk and remote buffer cache.

              Protocol C: write IO is reported as completed, if it has reached
              both local and remote disk.

       incon-degr-cmd command
              In  case  a node starts up in degraded mode (degr-wfc-timeout is
              set) and its local  replica  of  the  data  is  inconsistent  it
              executes  the  command.  If  the  command  exits  without error,
              drbddisk expects the DRBD device to be in primary state.

       device name
              The name  of  the  block  device  node  of  the  resource  being
              described.  You must use this device with your application (file
              system) and you must not use the low level block device which is
              specified with the disk parameter.

              The  device  nodes  must  have the same major number as the DRBD
              driver has. With the current implementation major  147  is  used
              and the corresponding device nodes are usually named /dev/drbd0,
              /dev/drbd1, etc.  ( All releases before drbd-0.7.1 used major 43
              and the device files /dev/nb*. )

              Installation   scripts   of   the  DRBD  package  provide,  that
              /dev/drbd0 to /dev/drbd8 are predefined in your  system.  To  be
              sure, issue something like ls /dev/drbd*.

       disk name
              DRBD  uses  this block device to actually store and retrieve the
              data.  Never access such a device while DRBD is running  on  top
              of  it.  This  holds  also  true  for  dumpe2fs(8)  and  similar

       address IP:port
              A resource needs one IP address per device,  which  is  used  to
              wait   for   incoming   connections   from  the  partner  device
              respectively to reach the partner device.

              Each DRBD resource needs a TCP port which is used to connect  to
              the node’s partner device.  Two different DRBD resources may not
              use the same IP:port combination on the same node.

       meta-disk internal

       meta-disk device [index]
              internal means, that the last 128 MB of  the  lower  device  are
              used  to  store  the  meta-data.  You  must not use [index] with

              You can use a single block device to store meta-data of multiple
              DRBD  devices.   E.g.  use meta-disk /dev/hde6[0]; and meta-disk
              /dev/hde6[1]; for two different  resources.  In  this  case  the
              meta-disk would need to be at least 256 MB in size.

       on-io-error handler
              handler  is taken, if the lower level device reports io-error to
              the upper layers.

              handler may be pass_on, panic, or detach.

              pass_on: Report the io-error to the  upper  layers.  On  Primary
              report it to the mounted file system. On Secondary ignore it.

              panic: The node leaves the cluster by doing a kernel panic.

              detach:  The  node  drops its low level device, and continues in
              disk less mode.

       sndbuf-size size
              size is size of the TCP socket send buffer.   Default  is  128K.
              You  can  specify  smaller  or  larger values. Larger values are
              appropriate for reasonable write throughput with protocol A over
              high  latency  networks.  Very  large  values  like 1M may cause
              problems. Even values below 32K do not make much sense.

       timeout time
              If the partner node fails to send an  expected  response  packet
              within  time  10ths  of a second, the partner node is considered
              dead and therefore the TCP/IP connection is abandoned. This must
              be lower than connect-int and ping-int.  The default value is 60
              = 6 seconds, the unit 0.1 seconds.

       connect-int time
              In case it is not possible to connect to the remote DRBD  device
              immediately,  DRBD  keeps on trying to connect. With this option
              you can set the time between two tries. The default value is  10
              seconds, the unit is 1 second.

       ping-int time
              If  the TCP/IP connection linking a DRBD device pair is idle for
              more than time seconds, DRBD will generate a  keep-alive  packet
              to  check  if  its  partner  is  still  alive. The default is 10
              seconds, the unit is 1 second.

       max-buffers number
              Maximal number of requests to be  allocated  by  DRBD.  Unit  is
              PAGE_SIZE,  which  is  4  KB  on  most  systems.  The minimum is
              hardcoded to 32 (=128 KB).  For high  performance  installations
              it  might  help,  if you increase that number. These buffers are
              used to hold datablocks while they are written to disk.

       max-epoch-size number
              The highest number of data blocks between  two  write  barriers.
              If  you  set  this  smaller  than  10  you  might  decrease your

       unplug-watermark number
              When the  number  of  pending  write  requests  on  the  standby
              (secondary)  node  exceeds  the unplug-watermark, we trigger the
              request processing of our backing storage device.  Some  storage
              controllers  deliver better performance with small values, other
              deliver best performance when it is set to  the  same  value  as
              max-buffers. Minimum 16, default 128, maximum 131072.

       ko-count count
              In  case  the  secondary  node  fails to complete a single write
              request for count times the timeout, it  is  expelled  from  the
              cluster.   (I.e.  the  primary  node goes into StandAlone mode.)
              The default is 0, which disables this feature.

       on-disconnect handler
              When the connection to the peer is lost, DRBD can either go into
              standd  alone  mode,  try  to  reconnect  to the peer, or try to
              reconnect and freeze application IO  while  not  not  connected.
              Valid   handler   specifiers   are  stand_alone,  reconnect  and
              freeze_io.  The default handler is reconnect.

              stand_alone: Do not reconnect, go into StandAlone state.

              reconnect: Try to reconnect.

       wfc-timeout time
              Wait for connection timeout.  The init script drbd(8) blocks the
              boot process until the DRBD resources are connected.  This is so
              when the cluster  manager  starts  later,  it  does  not  see  a
              resource  with  internal split-brain.  In case you want to limit
              the wait time, do it here.  Default is 0, which means unlimited.
              Unit is seconds.

       degr-wfc-timeout time
              Wait  for  connection  timeout,  if  this  node  was  a degraded
              cluster.  In case a degraded cluster (= cluster  with  only  one
              node  left)  is  rebooted, this timeout value is used instead of
              wfc-timeout, because the peer is less likely to show up in time,
              if  it  had  been  dead before.  Default is 60, unit is seconds.
              Value 0 means unlimited.

       rate rate
              To ensure smooth operation of the application on top of DRBD, it
              is  possible  to  limit  the  bandwidth  which  may  be  used by
              background synchronizations. The  default  is  250  KB/sec,  the
              default  unit  is  KB/sec.  Optional  suffixes K, M are allowed.
              Note that this is byte (octet) per  second,  not  bit.   We  are
              storage guys.

       group number
              Resynchronization  of  all  devices  in one group runs parallel.
              Groups are serialized in ascending order. You should avoid, that
              devices which lower devices share one and the same physical disk
              sync in parallel. The default group is 0. I.e. per  default  all
              devices   sync  parallel.  Negative  and  positive  numbers  are

       al-extents extents
              DRBD  automatically  performs  hot  area  detection.  With  this
              parameter  you  control  how  big the hot area (=active set) can
              get. Each extent marks 4M of the  backing  storage  (=low  level
              device).  In case a primary node leaves the cluster unexpectedly
              the areas covered by the active set must be resynced upon rejoin
              of  the  failed  node. The data structure is stored in the meta-
              data area, therefore each change of the active set  is  a  write
              operation  to  the  meta-data device. A higher number of extents
              gives longer resync times but less updates to the meta-data. The
              default number of extents is 127. (Minimum: 7, Maximum: 3833)




       This document is correct for version 0.7.20 of the DRBD distribution.


       Written  by  Philipp  Reisner  <>.  Man pages
       were    reviewed    and    rewritten    by    Helmut     Wollmersdorfer


       Report bugs to <>.


       Copyright  (c)  2001-2006 Philipp Reisner. This  is  free software; see
       the source for copying conditions.  There is NO warranty; not even  for


       drbd(8),    drbddisk(8),    drbdsetup(8)   drbdadm(8)   DRBD   Homepage

                                10 October 2007                   DRBD.CONF(5)