virtualbox.org

Hi Terry, VBox Users and Developers,

I would like to create VDI disk images that map every guest disk I/O to single host I/O.
I'll assume block size of 4KB.

Please confirm that the right size in MB is one of: 896, 1920, 2944, 3968, (896 + 1024X)MB ...
The above will be with zero padding (as we use the size for the correct alignment); actually any size which is by 1-127MB smaller of each of the above will work too.

Would it be better to enable a field in the first 512B which set the padding size so the first disk image's block will be on (2^BB)*512B, where BB is 0 ... 8 ?

Would it be nice if the GUI was rounding the image to one of those values - or at least give such recommendation?

The reason for all of these, is to reduce the number of I/O operations on the host, which are more noticeable in:
- Systems with some limit on number of I/O transactions
- High system stress, as we cut in half the number I/O, especially in random access with large images.

Thank you very much,

yes and no, and I know that this is what my All about VDIs says, but the issue is that by default logical heads are 63 blocks long. So unless you make your partitions start on 8 track boundaries, the clusters aren't aligned. I use fdisk advanced mode to set the disk configuration to N/64/32 (C/H/S) and if you do as you suggest the guest clusters and host clusters are aligned. When you reboot the BIOS reads the MBR info to determine what to report for the disk geometry, so the disk reports as a physical 64 head 32 sector disk. It doesn't give a huge payback but it does help.