Are independent persistent disks faster than dependent ones in vmware server 1?

Question

Please can you help me compare disk types for vmware server?

I know "independent nonpersistent" is slower. But what about "independent persistent" versus "dependent" (or how do you call this one?)

What about raw disks (direct access to physical disks)? And I found I cannot change the type from independent to dependent later? Is it possible to create a dependent raw disk when starting a new vm?

Answer 1

Hands down, "Raw Disks" is direct access to the physical disk and by far the fastest access and disk I/O. The downside is you cannot move the VM to another machine without imaging the raw disk.

----> I assume by raw disks you are talking about RDM but you should check http://www.vmware.com/files/pdf/performance_char_vmfs_rdm.pdf. Most of the time, RDM are not performing better than VMDK files.

Answer 2

Hands down, "Raw Disks" is direct access to the physical disk and by far the fastest access and disk I/O. The downside is you cannot move the VM to another machine without imaging the raw disk.

But, you asked which is the fastest "Virtual Disk". Raw Disks are not virtual disks.

And no, you cannot switch between virtual and raw types (unless I am missing an upgrade or something).

As for which virtual disk is faster? Fixed size is much faster than that dynamic type, which expands. Fixed disk is no where near as fast as Raw, but still much faster than dynamic.

Now, if you are asking if it makes a different to break the files into chunks or have one single large file - there are many discussions on the net that go both ways. Personally, having them split up into multiples I feel increases your host OS' seek time as it must go and find all different files, especially if you defragged your local drive.