Now that we know how VM discovery job works for a VMware Intelligent Policy (VIP), let us move on to the actual backup job. The process flow described here is the same for both VIP and browse-and-select type policies unless specified otherwise.
As we did in the previous blog, let us assume that the NetBackup master server, media server and VMware backup host are three different systems.
The bpbkar process loads VERITAS Mapping Services (VxMS) which among many other things, also implement VMware Disk Development Kit (VDDK) APIs. The VDDK APIs are used for reading from vSphere datastore. The real beauty of V-Ray comes from VxMS which has patent pending technology to map the stream during runtime and identify what is actually inside the VMDK file being read.
Here are some of the salient aspects of Symantec V-Ray within VxMS:
9.a) You are generating the catalog of all the files inside the VMDK (supported for VMDK files from both Windows and Linux VMs). Remember that this is not a two-pass process, the operation occurs while backup data is being streamed. This catalog information is send to master server via bpbrm process on media server.
9.b) As you are looking at file system inode level, you also get to identify unused and deleted blocks. This is quite powerful vision into the VM data. If the application on VM had allocated 1TB of space for a file, of which just 100GB is currently used, the backup stream would include just that 100GB. Similarly if you deleted a 1TB file that was fully allocated in the past, VxMS knows to skip the deleted blocks (unless the blocks are now allocated for a new file) from the backup stream. This optimization not only speeds up the backup stream, but it reduces needed storage even when deduplication is not enabled.
9.c) If source side deduplication feature is enabled, the VMware backup host does the deduplication. The NetBackup deduplication plug-in is not seeing just a giant VMDK file, it understands the mapping info generated by VxMS and hence it sees (with the V-Ray vision!) the actual files in the file system within the VMDK. This V-Ray vision is established by NetBackup deduplication plug-in loading a dedicated stream handler that understands the mapping info generated by VxMS.
9.d) Remember that all these operations occur at the VMware backup host. Your ESX resources (and hence the resources from VMs) are not used in these cases. This is true offhost backup with no burden on your production vSphere. Compare this with other vendors running index engines on VMs or helper VMs and including unallocated blocks and deleted files in all backups. Even the source side deduplication is happening in an offhost system in case of NetBackup for VMware.
For those new to NetBackup Deduplication, I would recommend reading this blog series. If you chose not to do deduplication at VMware Backup host (see 9.c), you are not losing V-Ray vision. The deduplication plug-in for media server deduplication pool, NetBackup 5200 series appliances and NetBackup 5000 series appliances also have V-Ray vision by making use of the dedupe stream handler which sees the actual files within a VMDK in backup streams. In fact, this V-Ray vision is one of the key differentiators for NetBackup deduplication when compared with third party target-only deduplication devices.
*For those new to NetBackup, the ‘bp’ in bpbrm, bptm, bpbkar etc. stands for ‘backupplus’, the old name of NetBackup.
**Although ‘t’ in bptm stands for tape, bptm has undergone significant overhaul during NetBackup 6.x. This process now handles tape as well as disk destinations.
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