(Re)claim your space!

In one of my previous posts, Is Bitlooker from Veeam a game-changer?, I wrote about the benefits of using Bitlooker for backup jobs when using Veeam Backup & Replication v9.x however Bitlooker is a feature that is not only available for backup jobs – you can use it for replication jobs as well.

So I thought it’d be fun to see what difference, if any, it makes. The goal of my tests is to figure out the most effective way of copying/replicating a VM from one host to another.

The set up for the test:

A virtual machine is installed with Windows Server 2016 standard edition. 100 GB disk assigned to the VM, thin provisioned. The disk is then filled with files (a bunch of iso-files of different sizes). That’s the baseline, then roughly 85 GB will be deleted (all the added iso-files) – then trashcan will be emptied. So we’ll have some blocks containing stale/old data, the blocks are marked as available to be reused from the operating system point of view but they haven’t been zeroed out so from any hypervisor (outside the VM) it just looks as any other block containing data.

Operating system installed (Windows Server 2016) and updated. The VM now consumes 13,5 GB worth of storage.

Then a bunch of files were added (almost) filling the entire disk.

From the vSphere side of it:

At this point the just added files were removed and trashcan emptied.

And from vSphere:

Now the command ‘ls’ will not show the actual size, so ‘du’ can be used instead to see the actual size of the vmdk file:

I’m going to test 4 different scenarios:

  1.  Migrate the VM from one host to another offline (VM will be shutdown).
  2. Replicating the virtual machine with VMware vSphere Replication 6.5.
  3. Replicating the virtual machine with Veeam Backup & Replication without Bitlooker enabled.
  4. Replicating the virtual machine with Veeam Bitlooker enabled.

The thesis, or point to prove, is that test 1-3 will have no or little impact on the size of the vmdk file however – magic will happen on test 4. So lets perform the tests and find out for real!

Test 1:

VM moved to another host while offline and now let’s explore what can be seen using different methods.

Inside the VM:

From the host:

So no change in vmdk file size as expected.

Test 2:

The virtual machine will be replicated to another host using VMware vSphere Replication 6.5.

VMware vSphere has been configured using the following settings:

Not alot of settings, in fact, the above settings will have no impact on the vmdk size. They will only have control how the snapshot on the VM will be generated (crash consistent vs consistent backup) and the impact the replication job will have on the network.

Inside the VM:

From the host:

Since ‘ls’ doesn’t show the actual size on a thin disk, disk usage ‘du’ is used instead:

So no change in vmdk file size as expected.

Test 3:

The virtual machine is replicated to another host using Veeam Backup & Replication v9.5.

Replication from a Veeam perspective has been set up, to make a fair comparison to the VMware replication test (test 2), the Veeam job will not use exclude swap file blocks:

Processed and read data in the picture below tells us that Veeam doesn’t know the difference between blocks in use and blocks marked as deleted (the same applies for almost all backup vendors):

Inside the VM:

From the host:

And using ‘du’:

So no change in vmdk file size as expected.


Test 4:

Know time for the fun stuff. The virtual machine will be replicated to another host using Veeam Backup & Replication v9.5. We will use both space saving techniques we can enable on the job (with application-aware processing we can also exclude specific files, folders, file extensions but we’re not using that feature in this test)

Now, this is the magic we were looking for! The  proxy server has processed all of the data but it has only read data that contain used blocks!

From the VM:

From the host:

Now the vSphere web client combine the .vmdk and -flat.vmdk file into one (like it’s done forever):

And the disk usage utility shows:

Yikes! That’s cool stuff!


Bitlooker is a feature you should have enabled on any relevant job. It certainly can be used to reclaim that precious storage space you so desperately need.  Heck, why no use it as part of your normal failover testing, cause you’ll already doing that right? Once a month (or how often you feel appropriate) do a planned failover using Veeam Backup & Replication, verify that you DR plan works and as an added bonus you reclaim disk space in the process!

And yet another benefit is the spent replicating the virtual machine, without Bitlooker it took 30 minutes to replicate the VM from one host to another but it was just shy of 7 minutes with Bitlooker enabled.

So seriously, why are you not using this magic thing? There’s only one drawback, Bitlooker supports only NTFS file system (=Windows VMs).

Is Bitlooker from Veeam a game-changer?

Disclaimer: This is not a performance comparison or test in any way, shape or form, it is merely my experience in a lab environment supposed to show an indicative relative difference in performance at a high level. OK, you get the picture?

So as you may know Veeam introduced a new feature in version 9 of Backup & Replication and I thought it would be fun to see if there were any actual benefits of using the feature called ”Bitlooker” by doing some basic tests. The goal of my test was to see if there were any differences in running backup jobs with or without backing up dirty blocks (i.e blocks that contains data but has been marked as deleted and thus the blocks can be reused by the operating system) which is the actual functionality of Bitlooker. My starting position was that logically it makes sense of course that it would be more efficient in a lot of ways using Bitlooker but I wanted to see if it was quantifiable: difference in speed and/or backup file size – again at a high level. And as an extended test I also wanted to see if there was any notable difference between using Bitlooker and SDelete (a tool from Sysinternals that you run inside the guest OS to clean up dirty blocks by writing zeros to those blocks).

Description of the Test environment
A Veeam Backup & Replication environment was set up, using simple deployment (all services on a single VM). A virtual machine running Windows Server 2012 was set up as the VM to be backed up running on a vSphere 5.5 host. Anyone familiar with the VMCE lab environment, that’s basically what I was using with and extended drive on on one of the domain controllers. The domain controller was assigned a 200 GB thin disk. I filled the disk with 190 GB worth of data, deleted 160 GB of data and then went ahead with some comparison tests. To describe what actually happens inside the OS at this point, only pointers to blocks containing information is deleted not the actual data on the blocks themselves which means that the OS will know the actual consumption on disk but for an outside observer (vSphere and Veeam for instance) it makes no difference: a block containing data is a block containing data.

Since I’m running the tests on my brand new toy, a Gen 6 Intel NUC which is not an enterprise server, I’m not that interested in the actual performance figures but rather the relative difference between the different test scenarios – all else equal. Oh, but there’s just one thing: Bitlooker only works with Windows and NTFS filesystem.

I initially performed some tests on a 40 GB VM but felt that, even though I saw some great improvements, I couldn’t draw any actual conclusions based on them.

I quickly realized – ”We’re gonna need a bigger boat!” and went for the 200 GB drive instead.

Since I already had performed some initial tests on my 40 GB environment the relevant scenarios at this point started at Test 8. All backup jobs were set up to take active full backup of the VM:

Test 8: A 200 GB vmdk where approx 40 GB was consumed. Basic backup test without Bitlooker enabled.

23 - Test 8 - Veeam GUI

24 - Test 8 - filesize

The resulting vbk-files from the 200 GB vmdk containing 40 GB of data is 12 GB in size.

Test 9: A lot of files were added to the VM, roughly 150 GB worth of data. Now the total consumed size of the disk is 191 GB. Again a basic backup test without Bitlooker enabled.

25 - Volume size pre-deletion of files

26 - VMDK size pre-deletion of files

A quick look shows the vmdk to be 200 GB in size.

27 - Test 9 - Veeam GUI

28 - Test 9 - filesize

With compression and deduplication the vbk-file ends up 95 GB in size.

Test 10: Now the fun begins, 163 GB of data was deleted and backup runs without Bitlooker.

29 - Size of files to be deleted

30 - VMDK size post deletion

Even though the files inside the OS has been deleted, the actual vmdk-file size doesn’t change and that’s expected behaviour from a thin disk. And it wouldn’t change even if you made a storage vMotion.

31 - Test 10 - Veeam GUI

32 - Test 10 - file size

This is  where it starts getting interesting, the vbk-file size is still the same size as we saw in the previous test: 95 GB! By logic it should be smaller since we’ve deleted 163 GB of data but clearly from the outside it doesn’t matter – a block is a block is a block.

Test 11: This is where we put Bitlooker to the test, same scenario as Test 10 but Bitlooker has been enabled on the backup job. That’s the only difference, a tick in a box.

33 - Test 11 - Veeam GUI

One big thing to highlight on the picture above is time spent backing up the virtual machine, 6 minutes compared almost 36 minutes in ”Test 10”. That’s a huge difference, and the end result will still contain the exact same active data from the VM.

34 - Test 11 - filesize

Massive reduction, we’re now seeing vbk-sizes similar to the first initial backup test in ”Test 8”.

Test 12: So let’s see if all types of ”zeroing”-techniques are equal. We’re now using SDelete to do it’s job on the C-drive zeroing out all deleted blocks and the backup job runs without Bitlooker.

35 - C drive zapped with SDelete

36 - Test 12 - Veeam GUI

It performs faster than ”Test 10” but slower than ”Test 11”, that’s interesting! I wasn’t really expecting such a big difference I must admit.

37 - Test 12 - filesize

The backup file size is identical as ”Test 10” though, and that was expected.

Test 13: So for fun let’s enable Bitlooker on the job, so SDelete and Bitlooker in conjunction.

38 - Test 13 - Veeam GUI

Bitsocker comes in to play again reducing the backup time to 6 minutes.

39 - Test 13 - filesize

No change in backup file size, that was expected. So there’s no benefit what so ever in this scenario of using SDelete.

Test 14 – Extra test: Since there was such a difference between ”Test 12” and ”Test 13” let’s verify the behaviour by disabling Bitlooker and run the job again. This should mean more time spent on the backup, right?

40 - Test 12 verification - Veeam GUI

Yep, we’re back again pushing past 23 minutes for the job.

41 - Test 12 verification - filesize

Backup file size doesn’t change.

Reducing the amount of data to backup from your virtual machines has always been a good thing, how ever historically it has been a manual or at least semi-manual task to accomplish, running SDelete.exe or some eqvivalent tool for instance. Perhaps running as a scheduled task but nonetheless it had to run on the VM itself and would require time and valuable CPU and I/O resoruces in the process. It was also prone to human ”error” since someone had to actual run the command or set up a schedule for it – meaning it might be forgotten or missed setting up new VMs. It’s worth mentioning that SDelete is a few years old and that there are other tools available you can use, one of which is a fling from VMware called GuestReclaim but I couldn’t use it in this case since it doesn’t work under Windows Server 2012.

Bitlooker changes the game completely, you literally only have to tick a box on a backupjob to make use of it! Faster backup times and smaller backup files, are there any drawbacks? Well yes and no, if you’re a windows shop go nuts with it but if you’re running any other OS you simply won’t be able to use Bitlooker.

Bitlooker is a great new feature from Veeam, not only does it reduce storage space required to hold your backup files but it also reduces backup time significantly for your active full backups (to be clear it will also make a difference on your incremental backups). As I already mentioned the tests were done on a tiny lab environment but it can still act as an eye-opener in terms of
relative difference with or without bitlooker enabled. Your own milage may vary, but you will see improvements. I tested 1 VM just for fun but I bet you have a lot more VMs, do you think you will save time? I’m sure of it!

”So what about cost? How much do I need to fork out for this great new feature you speak of?” I hear you say. That’s almost the best part: Nothing! You don’t need to pay anything! As long as you have a valid license and support contract you can just upgrade, it’s included in version 9 of Backup & Replication and for all editions: Standard, Enterprise and Enterprise Plus. For all new jobs created it’s even enabled by default and it can easily be enabled on your existing jobs – just tick the box. Thank you Veeam!

I would recommend enabling this feature on all your backups if you haven’t done so already. Period.

So ending with answering my question in the subject: Yes! It really is.