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dcm resynchronization does not start automatically

Created: 24 Jun 2013 | 1 comment

Hi all:

I am testing the vcs/vvr cluster . When I write a data which size exceeds the srl volume size, VVR goes to "logging to dcm" state. 

 

 # vradmin -g data_dg -l repstatus rvg_b
Replicated Data Set: rvg_b
Primary:
  Host name:                  192.168.100.111
  RVG name:                   rvg_b
  DG name:                    data_dg
  RVG state:                  enabled for I/O
  Data volumes:               1
  VSets:                      0
  SRL name:                   srl_b
  SRL size:                   150.00 M
  Total secondaries:          1
Secondary:
  Host name:                  192.168.100.112
  RVG name:                   rvg_b
  DG name:                    data_dg
  Rlink from Primary:         rlk_192.168.100.112_rvg_b
  Rlink to Primary:           rlk_192.168.100.111_rvg_b
  Configured mode:            asynchronous
  Latency protection:         off
  SRL protection:             autodcm
  Data status:                consistent, behind
  Replication status:         logging to DCM (needs dcm resynchronization)
  Current mode:               asynchronous
  Logging to:                 DCM (contains  5572672  Kbytes) (SRL protection logging)
  Timestamp Information:      N/A
  Bandwidth Limit:            100.00 Mbps
  Compression Mode:           On
After writing, the vvr keeps in  "needs dcm resync"  status and the resynchronization does not start automatically. What should I set to let the resync start auto?
 
Btw:another question. If a new write operation on block operation coming in when the block is in dcm resync state, is the write action blocked or not? 
Operating Systems:

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mikebounds's picture

 

When VVR catches up from SRL, the secondary is consistent as it is written on the secondary in the same order it was written on primary.  With DCMs VVR cannot catch up consistently as it is just writing the dirty regions in the DCM with no write-order so as VVR can only catch up inconsistently using the DCMs maps, this is a manual operation, so you are aware your DR site will be inconsistent during the catch-up (so back-up of the DR site is recommended before you start DCM resync, just in case you loose primary during catch-up).  To catch up use:
 
vradmin -g dg_name resync rvg_name
 
I don't believe there is anyway to automate this with VVR tools, but I would not recommend this anyway.
 
During DCM resync, writes on primary still continue.
 
Mike

UK Symantec Consultant in VCS, GCO, SF, VVR, VxAT on Solaris, AIX, HP-ux, Linux & Windows

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