Slow Backup Performance? How to Speed up Backups

slowIt’s a general knee jerk reaction to blame your backup solution for being slow; however, slow backup performance is usually caused by many other factors. Whether you use Windows Server Backup, Veeam, BackupChain, or Acronis, when used in the same underlying infrastructure the bottleneck may be identical; hence, you’ll want to identify the real bottleneck in your setup.

You can speed up your backup process considerably and identify slow performers by using this checklist below:


 Check for orphaned VSS snapshots and delete them

On some systems the hardware is so slow that people get impatient and terminate the backup process before it finishes.

This should never be done. Backup services should never be terminated by hand, unless it’s an emergency or last-resort situation.

Because if you do kill the process, no clean up occurs and the server gradually fills up with garbage shadows, a.k.a. orphaned shadows.


VSS Snaphots are somewhat tricky to understand. Basically each snapshot tracks the previous state of the drive, while new changes are written directly to disk. As you can imagine, if you have many snapshots the system will be very slow when reading as well as writing, since it needs to manage each snapshot separately all the time.

Some users deploy VSS snapshots to enable file version recovery through Windows Explorer. That’s fine if there is just one shadow, but if you have many, you basically burn expensive, ongoing¬†server performance for something that a backup solution can do much better in a short period of time. Consider using backups instead at regular nightly intervals.

To check for and clean up VSS snapshots, open the command prompt as administrator and use vssadmin.exe list shadows as shown below:


vssadmin list shadows

On Windows Server 2008 and later, there’s a nice UI tool available for this as well, in case you have command prompt phobia, it’s called VSSUIRUN.EXE.

As you see above, the system is clean. If it wasn’t there would be a range of shadows in the system. Note that during backups you will see the actual shadow listed there, so don’t delete it while the backup is active.


Increase Shadow Storage Area

VSS is error prone when it runs out of space. Use vssadmin (or VSSUIRUN.EXE if available) to increase the VSS area limits for all drives.

The command

vssadmin list shadowstorage

will report on the current allocation limits.

Use ‘vssadmin resize shadowstorage’ and set all drives to ‘unbounded’ or a very large portion of the disk’s space.

Note that this is only a limit, VSS won’t actually use it unless it has to.

vssadmin resize shadowstorage


Free Disk Space

Another common reason for slow backups and actually slow overall system performance has to do with how NTFS operates.

You should aim for 20% free disk space to keep the system running optimally. Less than that and write access will slow down considerably. In addition, disk fragmentation will be highly likely resulting from a near-full disk in the future, which in turn will slow down read accesses as well.


Turn off System Restore

Turn off System Restore (on desktop versions of Windows) or scheduled VSS snapshot creation (on Windows Servers). System Restore is supposed to help you return your PC to a bootable state, for example, when you install drivers and it blue-screens.

However, as noted above, VSS slows down the system too much to make this a feasible option, especially when System Restore runs on a schedule and creates many shadows over time. Consider using system backups instead. The backup will run once and consume a lot of resources when doing so, but once finished the system returns to full capacity for your other applications. This type of backup strategy is advantageous especially for lower powered systems.


Disk Fragmentation

Disk fragmentation is highly recommended for source drives as well as backup disks.