DR Design Limitations for Active-Active Data Center

Last post 10-13-2019, 10:57 PM by Watson. 6 replies.
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  • DR Design Limitations for Active-Active Data Center
    Posted: 09-24-2019, 1:45 PM

    DC1 houses primary services presently. A warm DR DC2 site exists with networking and minimal compute, etc., but no CommServ at the DR DC2 site. There is a 3rd location DC3 with off site AUX copy on a SAN and media agent only. Cold DR in other words. DC3 will be closing.

    We are planning to occupy both DC1 and DC2 and are designing active-active paired data centers where either DC could assume full prod workload capacity if we suffer loss of the other DC. Assume there is data at both DC1 and DC2 which must be backed up and preserved in case of disaster.

    As I understand CommVault DR capabilities, we could have a primary CV1 at DC1 with a DR CV2 at DC2 utilizing SQL mirror to maintain DB consistency at both DC1 and DC2. The DC1 data would be backed up to DC2 storage. The DC2 data would be backed up to DC1 storage. Can CV simultaneously backup the local data while simultaneously be a DR CV for the remote location? Or do I need 4 CV servers to pull this off?

    Maybe a picture would help? Which configuration is valid:

    1. Two CommServ servers:

    DC1CV1  <--> DB mirror <-->  DC2CV2

    2. Four CommServ servers:

    DC1CV1      --> DB mirror -->  DC2DRCV1

    DC1DRCV2 <-- DB mirror <--  DC2CV2

    Finally, how would we license the above scenarios? 

  • Re: DR Design Limitations for Active-Active Data Center
    Posted: 10-04-2019, 6:44 AM

    Hi GeorgePerkins

    In Commvault you can only have one active CommServe at any time, in saying that the valid configuration will be 

    1. One CommServ servers (the correct technical terminology):

    DC1CV1  <--> DB mirror <-->  DC2CV2

    Leveraging SQL mirroring to ensure the Secondary Passive CommServe is in-sync. 

    As both DC1 and DC2 are both active sites (doing local Backup), all you need to do is to ensure the DASH Copy is up to date. 

    Two possible Scearnio:

    • Scenario 1 - you lose your Primary CommServe, the Secondary CommServ will become active and will be able to communicate to the Clients and MediaAgent on both Site. 
    • Scenario 2 - you lose the entire DC1 site, you still have a replicated copy of the Backed up data (as DASH Copy), brind up the Secondary CommServ, and you are still able to Backup (Clients on DC2) and be able to restore anything which belongs to DC1.
    Once you resolve the issue on DC1, you sync up the SQL mirroring and continue the Backup and Dash Copy. 
     
    Regards
     
    Winston
  • Re: DR Design Limitations for Active-Active Data Center
    Posted: 10-07-2019, 12:50 PM

    Winston, thanks for the reply. What do you mean by "One CommServ servers (the correct technical terminology): DC1CV1 <--> DB mirror <--> DC2CV2" (That still looks like two CommServ servers to me).

    Also, regarding licensing,

    I found [https://documentation.commvault.com/commvault/release_9_0_0/books_online_1/english_us/prod_info/dedup_disk.htm?var1=https://documentation.commvault.com/commvault/release_9_0_0/books_online_1/english_us/features/dash_copy/dash_copy_basic.htm]

    Which states:

    DASH Copy requires following licenses based on the License Type:

    For Traditional License, Block Level Deduplication license is required on the MediaAgent hosting the deduplication store.
    For License Usage by Capacity, Data Protection Enterprise (for Backup) or Archive Enterprise (for Archive) license is required.


    Looks like if CommServ relies upon SQL database mirroring, then the SQL Server Enterprise Edition would be a requirement. Please see [https://docs.microsoft.com/en-us/sql/database-engine/database-mirroring/prerequisites-restrictions-and-recommendations-for-database-mirroring?redirectedfrom=MSDN&view=sql-server-2017] and [https://docs.microsoft.com/en-us/sql/sql-server/editions-and-components-of-sql-server-2016?view=sql-server-2017#RDBMSHA] and [https://docs.microsoft.com/en-us/sql/database-engine/database-mirroring/database-mirroring-operating-modes?view=sql-server-2017].

    Which recommends:
    Optimal database mirroring performance is obtained by using asynchronous operation... Most editions of SQL Server 2017 support only synchronous database mirroring ("Safety Full Only"). For information about editions that fully support database mirroring, see "High Availability (Always On)" ...

    My interpretation is only Enterprise Edition supports asynchronous operations aka "High Availability (Always On)".

     
  • Re: DR Design Limitations for Active-Active Data Center
    Posted: 10-08-2019, 1:43 AM
    An always-on CommServe is best achieved through clustering.
    https://documentation.commvault.com/commvault/v11/article?p=5025.htm
    Commvault has CommServe LiveSync which is highly available and the frequency of the log shipping is fully configurable.
    If backups and restores require very high availability (e.g. five-nines or greater) then perhaps discuss this Commvault Professional Services or a Certified Partner for more details.
  • Re: DR Design Limitations for Active-Active Data Center
    Posted: 10-08-2019, 10:32 AM

    Anthony, This is not a question about HA, this is DR. The DCs are geographically distant and not a case for HA clustering. DC1 backs up DC1 data. DC2 backs up DC2 data. DC1 is a DR site for DC2. DC2 is a DR site for DC1.

  • Re: DR Design Limitations for Active-Active Data Center
    Posted: 10-13-2019, 3:46 AM

    Hi GerogePerkins

    Apologies for the late reply. 

    You are correct "What do you mean by "One CommServ servers (the correct technical terminology): DC1CV1 <--> DB mirror <--> DC2CV2" (That still looks like two CommServ servers to me)." (apologies for the confusion)

    I meant there will always be one Active Instance of the CommServe running, with a second Instance on each of the CommServe Server doing log-shipping if you are planning to doing mirroring. 

    I do notice you are looking at documentation from V9 in regards to licensing. 

    With the new licensing models (Commvault Complete, Orchestrate, Activate & HYperscale) the capacity and socket licensing will be added on top. For further details I would highly recommend to engage your Account personnel to get a better quote on the licensing aspect. 

    In regards to the exact version required for SQL, might be advisable to open a Support Ticket to double confirm

    Regards

    Winston 

  • Re: DR Design Limitations for Active-Active Data Center
    Posted: 10-13-2019, 10:57 PM

    Hi George,

    For a single Commcell Id, you cannot have Active/Active you can only Active/Passive.

    You could have the following 

    DC1DC2

    Prod_CSDC1 -> DR_CSDC1

    DR_CSDC2 <- Prod_CSDC2

     

    However a more cost effective scenario would be 

    DC1DC2

    Prod_CSDC1 -> DR_CSDC1

    Local MediaAgent        Local_MediaAgent 

     

    The local MediaAgents would be registered to Prod_CSDC1 and both DCs would dashcopy jobs from their local Media Agent/Disk Library.

     

     

     



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