SNDR (Remote Mirror) cheat sheet

Remote Mirror (SNDR/RDC), creates a network based mirror between two raw devices. When replicating, writes occur on the Primary Host's device no writes occur on the secondary host. When logging, writes may occur on either side, and are tracked through bitmaps.


Primary Host Contains primary device. All commands that manipulate the SNDR-set occur here after the set is enabled.
Secondary Host Contains secondary device. The only command run here is the "enable" command, when the set is first created
Scoreboard A bitmap. There is a bitmap for both primary and secondary devices. Bitmap becomes active when the SNDR-set goes into a "logging" state. Each bitmap tracks changes in the associated device when in "logging" mode.
Set The relationship of:
Primary Host, Primary Device, Primary Bitmap
Secondary Host, Secondary Device, Secondary Bitmap

Which version?

# pkginfo -x SUNWrdcr

What packages installed?

2.x SUNWspuni SUNWscm SUNWspsv SUNWrdcr SUNWrdcu
3.x SUNWscmr SUNWscmu SUNWspsvr SUNWspsvu SUNWrdcr SUNWrdcu

What processes?

2.x rdcd and rdcsyncd
3.x sndrd and sndrsyncd

What drivers loaded?

# modinfo | egrep "(nskern | sdbc | nsctl | rdc | sv | iidev)"

What configuration?

  • Output from:
    # /usr/opt/SUNWesm/sbin/sndradm -i
    # /usr/opt/SUNWscm/sbin/dscfg -l
    # /usr/opt/SUNWesm/SUNWsvsp/sbin/svadm
  • What are my tuneable settings for each set?
    # sndradm -P
  • What are the states of my sets?
    # scmadm -S -M
    states can be:
      logging, sync, reverse sync, or replicating
  • What ports does SNDR use? From /etc/services
    # grep rdc /etc/services
    rdc        121/tcp
    check for the port by:
    # netstat -an | grep 121

Name resolution?

SNDR comes up before DNS, NIS, and NIS+. The /etc/nssitch.conf should point to files for hosts and services. Only hosts that are in use by SNDR need be identified in the /etc/hosts table.

Useful commands

/usr/opt/SUNWesm/sbin/sndradm sndradm is equiivalent to rdcadm which is found in the same directory
/usr/opt/SUNWscm/sbin/dscfg manipulates the data services configuration location
/usr/opt/SUNWesm/SUNWspsv/sbin/svadm manipulates sv driver layer
/usr/opt/SUNWesm/sbin/sndrstat shows statistics and state of SNDR-set NOTE: All sndradm commands can be substituded for rdcadm commands for 2.x version of the software.