VMware filesystem alignment what's about guest systems

mpi,
This was recently asked in another context; the guidance that was provided is below as this may be helpful to you.

~~~
It is very difficult to align boot volumes. You can do so in a VMware environment if:

the boot disk is a RDM device where an aligned partition is created on the service console, and that partition is marked as type 7 (NTFS).
(ii) The disks are deployed using a template or an exported disk image that was created for an aligned partition.
(iii) Use of CLARiiON LUN alignment is utilized.

In general the IO to boot disks in modern systems are small block random IO to page files. If the system is designed properly the IOs to boot disk should be minimal. This is one reason why it's recommended that the boot disks on VMFS-2 volumes be separated from the volumes that will see much larger IO rates (i.e., application data).
~~~

Regards,
DGM

Thanks for your answer.
"many a little makes a mickle"
If I have several Virtual Machines on one VMFS I'll get also a lot of I/Os on the LUN. (in one project: 450 GB LUN with 40 VMs generates between 300-800 IO/s, so 8-20 I/Os per VM) and on the LUN I also recognize disk crossings. The VMFS Partition is aligned due to the creation through virtual center, but the Boot Disk are not. So do you recommend to leave it as it is or to start to deploy aligned boot partitions (however we'll realise it)?

mpi,
Guidance from the performance community is that if you are not having performance issues now, then there is no reason to re-architect. Going forward, including alignment as part of your deployment strategy may allow you to load more VMs on a single set of drives, but the difference would be small: only 6% of typical random I/O in a Windows environment will be causing a disk crossing.

Regards,
DGM

Hello DGM,

Thank you for your response.
For the next VMFS LUN we'll create aligned VMware Templates. We'll use a WinPE Boot CD to create the partition aligned.

Regards
mpi