AnsweredAssumed Answered

Shadow Image with and without Consistency Group (CTG)

Question asked by Swee-Chin Liem on Nov 20, 2014
Latest reply on Nov 26, 2014 by Swee-Chin Liem

Hi Experts,

 

I confuse with SI with/without CTG... Can you please advise dummy like me?

 

Let's say my HORCM files are something like this (two dev_group):

HORCM0 (PVOL)

#dev_group  dev_name  Serial#  CU:LDEV(LDEV#)  MU#   

Host01      SIDEV00   12345    00:00            0

Host02      SIDEV01   12345    00:01            0


HORCM1 (SVOL)

#dev_group  dev_name  Serial#  CU:LDEV(LDEV#)  MU#   

Host01      SIDEV00   56789    10:00            0

Host02      SIDEV01   56789    10:01            0

 

If my SI are created as below:

  • Host01: With CTG 1 (-m grp 1).
  • Host02: With CTG 1 (-m grp 1) too.

 

Question 1: What will happens, if I issue "pairsplit -g Host01"?

  1. Only pair for LDEV 00:00 get split.
  2. Both pairs for LDEVs 00:00 and 00:01 get split.
  3. ?


Question 2: What will happens, if I issue "pairsplit -g Host02"?

  1. Only pair for LDEV 00:01 get split.
  2. Both pairs for LDEVs 00:00 and 00:01 get split.
  3. ?

 

Let's say my HORCM files are something like this now (one dev_group):

HORCM0 (PVOL)

#dev_group  dev_name  Serial#  CU:LDEV(LDEV#)  MU# 

Host01      SIDEV00   12345    00:00            0

Host01      SIDEV01   12345    00:01            0


HORCM1 (SVOL)

#dev_group  dev_name  Serial#  CU:LDEV(LDEV#)  MU# 

Host01      SIDEV00   56789    10:00            0

Host01      SIDEV01   56789    10:01            0

 

If my SI are created as below:

  • SIDEV00: With CTG 1 (-m grp 1).
  • SIDEV01: Without CTG.

 

Question 3: What will happens, if I issue "pairsplit -g Host01"?

  1. Split failed, pairs remain as it is.
  2. Both pairs for LDEVs 00:00 and 00:01 get split.
  3. ?

 

Question 4: What is so special of CTG?

Document that I found mention that it can ensure all pairs belong to same CTG split at the same time; but how? I mean, how to split pairs using "CTG" instead of "dev_group" (pairsplit -g Host01)?

If I don't use CTG, I split pairs using "dev_group", it will still split all my pairs at the same time too, isn't?

 

Thank you.

Outcomes