What does the memory bitmap means in the vmware Vmotion process?

[zhangfred_vm]

Hi Friends,

In the vmotion process, (From VMworld06 documents)

1. Precopy the memory from ESX1 to ESX2. then log the ongoing memory change into a memory bitmap in the esx1.

2. Quiece the virtual machine in the ESX1, then copy the memory bitmap from ESX1 to ESX2.

3. Start the VM in ESX 2, now the user access the VM on ESX2.

4. Copy the Vm's remain memory from ESX 1 to ESX 2 (which listed in the memory bitmap file) . Fetch memory from the source VM when application want to read/write the modified memory in VM on ESX2.

I have some questions:

1) what does the memory bitmap means? It is file just to record the change memory address?

2) what the "Fetch memory from the source VM when application want to read/write the modified memory in VM on ESX2." means?

Thanks.

[weinstein5]

This process has changed somewhat with ESX 3.5/VC2.5 - Step 4) Copy the memory pages that have changed as listed in the Bitmap before the VM is restarted - so there is no need to 'fetch the memory pages that have changed' - the memory bitmap still contains the same information - a list of the memory pages that change while the memory is being copied over from ESX1 to ESX2

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