Using CDR to replicate NFS?

Last post 10-29-2014, 1:56 PM by jmills. 7 replies.
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  • Using CDR to replicate NFS?
    Posted: 10-29-2014, 10:58 AM

    Is there any way to replicate NFS shares using CDR? It doesn't appear to be supported and from my testing it doesn't seem to like an NFS file system as the source (seems to be ok as the destination).

    I have a Celerra Gateway with NFS shares that I want to replicate to another Celerra Gateway in another Data Center.


    -J. Mills
    Systems Engineer (Storage & Backup)
    CommVault Certified Master

  • Re: Using CDR to replicate NFS?
    Posted: 10-29-2014, 12:13 PM

    Jmills, 

           You are correct with your findings that with CDR it does not support NFS shares as the source of the pair, destination as you stated will be fine to use the share.  CDR requires that the source be a local volume on the source server.  You may want to look into utilizing Dash copy, Dash copy is the "Replication" method of moving your source data that has been backed up to the destination.  This will be the transfer of your data that has been backed up from a source Media Agent to a destination Media Agent.  The difference between the 2 is that CDR will Replicate over files that have not been backed up but Dash copy will only move chunk files from the Media Agents so the data that you want to transfer must be backed up first.

    Thank You

  • Re: Using CDR to replicate NFS?
    Posted: 10-29-2014, 12:17 PM

    I am a little confused by your response. I understand Dash Copy as a Deduplicated Aux Copy, but I am not understanding how I could use that to keep two NFS shares replicated. I am looking for something near real time synchronous like CDR would provide.


    -J. Mills
    Systems Engineer (Storage & Backup)
    CommVault Certified Master

  • Re: Using CDR to replicate NFS?
    Posted: 10-29-2014, 12:26 PM

    Jmills, 

    If the need is the get the data from a source server to a destination location you can accomplish this by backing up the data first and then allowing Dash to move the chunk files.  This is an option that you could use to move the data but as far as CDR is concerned you have no ability to use the NFS share as the source location for the pairs as this is not supported.

  • Re: Using CDR to replicate NFS?
    Posted: 10-29-2014, 12:33 PM

    OK, thank you. I was hoping someone had some trick up there sleeve. Is there a technical reason why CDR will not work with NFS, or is it something that I could put a CMR in for?


    -J. Mills
    Systems Engineer (Storage & Backup)
    CommVault Certified Master

  • Re: Using CDR to replicate NFS?
    Posted: 10-29-2014, 1:11 PM

    CDR utilizes VSS to snap the source volume to ensure that we capture and replicate any files that are opened or locked.  VSS is unable to snap a NFS share so the pairs will fail with unable to take a VSS snap

  • Re: Using CDR to replicate NFS?
    Posted: 10-29-2014, 1:24 PM
    • efg is not online. Last active: 08-22-2019, 5:13 PM efg
    • Top 10 Contributor
    • Joined on 02-02-2010
    • CommVault Tinton Falls NJ
    • Expert
    • Points 1,672

    With Unix/Linux CDR it involves loading a device driver and replacing the mount point (from the local device) to a device created by the cdr module that gets loaded into the kernel.  This won't work with NFS as NFS is also a module loaded into the kernel, and these will interfere with each other.

    This is why (on the source) you see the mount point change from /dev/dsk/xxxxx to /dev/cxbf/cxbfN.  It also explains why (during configuration) any applications running on the source path need to be shut down (for the remount of the file system to occur)

    The destination can be on an NFS mount because no driver is required for the destination.


    Ernst F. Graeler
    Senior Engineer III
    Development
  • Re: Using CDR to replicate NFS?
    Posted: 10-29-2014, 1:56 PM

    Thanks, that makes sense now. I will start looking at other tools.


    -J. Mills
    Systems Engineer (Storage & Backup)
    CommVault Certified Master

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