Difference between REDO logs and VM Snapshot?

[RockyConcept]

I am asking very basic question, not sure this is right forum to ask.

1) What is difference between REDO log and Snapshot ?
2) How to enable the redo logs for a VMDK on the ESX and VM Workstation ?
I am talking about the VMX parameter.  I see parameter called scsi0:0.redo = ""  redoLogDir = "."

Any inputs or document would be of great help.....

Regards

[idle-jam]

in fact it's the same thing just with different way of calling it.

[RockyConcept]

I am little confused with these two different terms meaning the same stuff.

I reffered the below links, and I got more confused :

http://stuff.mit.edu/afs/sipb/project/vmdialup/lib/vmware-console/help-manual/disks_fileinfo_gsx.htm

http://www.vmware.com/support/ws55/doc/ws_learning_files_in_a_vm.html

Chances are that my understanding is worng, but your comments will help me to make it clear.

At some places its documented that Name-REDO.VMDK will be created when you enable a redo VMX parameter for VMDK. But in case of snapshot the file will be Name-000001.vmdk.

I am not sure whether term REDO is used for earlier version of ESX 3.X /GSX/Workstation 5.5. I didn;t find any document on this but just a guess.

Surprisingly I can see below parameters in VMX ( Workstation 7.0), but don;t see Workstation creating any REDO files...

scsi0:0.redo = ""

redoLogDir = "."

Any help or pointers would be helpful.

[continuum]

earlier versions of Workstation did not allow hot snapshots - (snapshots while the VM is running)
in those days the naming conventions were a bit different
ide0:0.redo = "hd1.vmdk.REDO_a00992"

see http://sanbarrow.com/vmx/vmx-undoable-mode-for-vmserver.html

when version 4 appeared - first time allowing hot snapshots the naming conventions were changed.

basically this both terms are exchangable

[admin]

To add to what has been said before, they are essentially the same thing but with different naming conventions under different scenarios.

So today when you create a snapshot, the delta disk(redo logs) created are given names *-000001.vmdk and so on.

But presently the parameters you specify "scsi0.0.redo" are used when you create a non-persistent virtual disk.

When you power on a VM, you will see a delta disk with the name *REDO being created and entries

scsiX:X.mode and scsiX:X.redo being filled up. This redo logs will be deleted once you power off your VM or restore to a snapshot.

scsi0:1.mode = "independent-nonpersistent"
scsi0:1.redo = "./SUSE Linux-0.vmdk.REDO_IueETT"

I hope this clears your doubts.