2 Replies Latest reply on Jul 16, 2008 10:56 AM by jfrichard

    Virtual Consolidated backup

    timcwhite Enthusiast





      In the very near future, we are going to install VCB to perform our backups. This will be used along with netbackup. My understanding is that VCB will create a snapshot of the vmdk's that it will back up, place it on the VCB proxy server, then netbackup will grab the file and write it to tape. What happens to the new information that will be written as the vmdk is being copied/backed up? is this information going to be stored in memory or on disk until the snapshop is finished. I'm concerned that we will run out of space on our LUN where the vmdk file is located until the snapshot is deleted. Is this a valid concern?












        • 1. Re: Virtual Consolidated backup
          lamw Guru
          VMware EmployeesCommunity Warriors

          You're correct that it takes a snapshot, it basically quieces the filesystem so that no more writes occur, all changes will be in redo/snapshot .vmdk. VCB will then mount up (filelevel) or just copy the .vmdk to your external storage, whatever that maybe. Once the copy has occured, it'll unfreeze the VM and the comit will occur to apply all changes back to the primary .vmdk. Since it's talking directly to the SAN depending if its FC / iSCSI, it goes pretty fast and huge changes hopefully won't be taking place during this period. You can setup schedules on when you want the backup to occur and that hopefully should allieviate some of the high load on the VMs during the snapshots. Also it's best practice to only do 1-2 backups on a given LUN so you don't impact other VMs, so you only concern is space on your external filer not on the SAN itself, especially if you follow the best practice of have only 1-2 active backup per LUN. It's always good to keep a good buffer of space on your LUNs, in case of snapshot creation and that number can be 10-20% free space of the LUN.

          • 2. Re: Virtual Consolidated backup

            The snapshot is created when the command is initiate by the backup utility.  Yes, you have to care about the space but remember that this process is fast so you don't need a lot of space on the datastore.