The problem of inevitable degradation of the disk subsystem performance caused by misaligned
partitions dates back to the nineties. From being a headache for IT administrators who wanted to
get the most out of disk arrays, it has now become crucial for all of us with appearance of SSD
(Solid State Drive) and ultra high-capacity AFD (Advanced Format Drive). Moreover, the growing
popularity of virtualized systems has aggravated the situation even more.
Virtual hard drives are using page sizes similar to those of the modern AFD or a 4K physical
sector size hard drive. As you know misalignment is very common for this type of drives resulting
in redundant read/write operations, which is critical for the overall performance and indirectly
hardware lifespan. So it is for virtual hard drives – even a simple migration of a virtual machine
from one VMware ESX Server to some other could end up with a misaligned virtual drive. The
situation aggravates when the host’s hard drive and virtual drives are both misaligned – the number
of redundant read/write operations obviously doubles.
A New Solution from Paragon
PAT for ESX is the next generation of the best-selling classical PAT that is aimed exclusively
at optimizing virtual drives. It’s been designed primarily for IT personnel who administer Windows
or Linux guest environments that are running on VMware ESX Server. However, it can also be very
useful for improving the disk subsystem performance of guest operating systems under control of
Microsoft Hyper-V Server.
Unlike its predecessor, PAT for ESX allows alignment of virtual hard drives without the need
of installation within every guest OS. You just install the product once either on a physical or
virtual machine based on Windows XP SP3 or later, and then you get access to and align any
supported virtual drives stored locally or remotely. So in case of having to do with an MS Hyper-V
environment, you should install the software directly on the host, while for VMware ESX you’ve got
the choice either to do the alignment from one of its Windows OS guests or from the outside*, both
ways through the VMware ESX infrastructure.
Here’s how it works:
Why try PAT for ESX?
Requires minimum free space (3-4MB) for accomplishing disk alignments
Doesn't need additional space on the datastore for a snapshot or image of the aligned at the
Completes interrupted alignments caused by a system failure, reset, or even a power
Allows several levels of data safety from outer failures (power outage, etc.) to specify
the acceptable balance between performance and potential data loss
Doesn't need the root account or any other special account for work - an account with
sufficient privileges for the target virtual machine is enough
Supports ESX, ESXi (commercial versions), and vSphere
Supports VMware CBT (Changed Block Tracking)
Can be installed and run on any Windows OS since Windows XP SP3
Aligns hard drives inside virtual environments based on any Windows OS since 2000 as well as
Aligns disks inside guests of VMware ESX Server from one of its Windows OS guests or a
Aligns disks inside guests of vSphere controlled by vCenter
Aligns disks inside guests of Microsoft Hyper-V R1/R2 directly from the host
Aligns any of the supported virtual disk types stored locally or remotely
Enables to schedule alignments or create alignment scripts for later execution
Supports not only drives formatted to NTFS and FAT file systems, but Linux Ext2/3/4FS
* Operation from a computer outside the VMware ESX infrastructure is slow in performance and
may heavily load up the network when aligning many drives at a time, so we do recommend you to
install and use PAT for ESX from a Windows OS guest running on a ESX host that has access to
datastores with virtual drives you’re planning to align.