I have a piece backup software that supports two options for backing up VMware virtual machine - one is just backing up VM's files (taking a snapshot first) and the other using vStorage API. The first option can backup VMs from the free version of ESX(i) the other only works with the paid version. So, I see an immediate disadvantage of using vStorage API - we would have to pay $500 for VMware license, but I assume there should be something good that compensates for this, right?

VMware is avoiding the fact that it is really easy to backup VM files if your storage is on NFS, so they keep quiet about this and only promote vStorage API. I have a feeling that there is nothing substantial in this API and they just want more money. Could someone speak from experience and shed some light on REAL advantages of using vStorage API for backups?

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I'm no VMware expert, but one advantage of the vStorage API's is that they allow 'changed block tracking'. In effect the backup software is supplied with a list of which blocks have changed since the previous backup, and it can ask VMware on which storage these blocks are stored.

This allows the software to retrieve the minimum amount of data directly from a SAN. Ultimately it means backups are very fast, LAN free and are “localised” to the backup server.

The backup software we use, Veeam Backup & Replication, performs very fast backups this way. Straight from the SAN over a single 1Gb iSCSI connection.

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If you weren't using NFS, the advantages would be a lot more obvious.

FC and iSCSI storage on VMFS filesystems means you need something to grab the data out; vStorage APIs serve that purpose.

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  • The software does not do it on NFS level, it can backup any storage type. I think it just logs in to ESX server, takes snapshot, goes to datastore, downloads relevant VM files, removes snapshot. So, no API is needed fro this. – dtoubelis Apr 14 '11 at 19:53

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