VMware virtual HD performance with Truecrypt on the host - Use 2 GB chunks?

Question

Configuration:

I am using VMware on a laptop computer, which is truecrypted as a theft precaution. The VHDs are ceated as single growable files (i.e. not split in 2 GB chunks, no preallocation of whole VHD space.) Host: Windows7 64bit. Guests: Windows7 32bit and WindowsXP 32bit. VMware version: VMware player 4.0.x.

Problem:

When using the VMs extensively, I often experience painful minutes of 100% I/O activity on the host HD. This of course slows everything down. According to "Perfmon /res", the culpable host processes are system and "vmware-vmx.exe", ("system" consuming the lion share). There is big read AND write traffic, regardless of what I did in the VMs. The problem seems to be worse with Windows7 guests that with WindowsXP clients.

Excluded causes: Perfmon confirms that there is enough real RAM. The antivirus on the host is configured to skip all file types which occur in the VM folders.

Q:

Are there any Truecrypt operations affecting the whole VHD file on the host, when I made a write-access to a small portion of the VHD from within the VM? Would it therefore help to split the VHD files into 2 GB chunks?

Or is this a stupid thought because the Truecrypt ciphertext block size is just 16 bytes?

Any other idea out there?

Answer 1

You can safely presume that TrueCrypt has linear performance footprint because full disk encryption is implemented as a block-level driver.

VMware, on the other hand, is slow with dynamic volumes. I have seen similar effects with and without TC. So a possible solution would be to use fixed VHDs.