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Backing up VM image files to Internet backup services



Code 42, decision makers for the CrashPlan Small Business Backup Service (but not individuals, see "CrashPlan Discontinues Consumer Backups," August 22, 2017), has announced that, from May 2019, the service will no longer allow users to backup programs, virtual machine files from apps such as Parallels Desktop and VMware Fusion, and some backup files.

  E-mail message from Code42

Code42 explains the change by saying that the omission of these files is likely to result in smaller backup files and more quickly recover, sync and back up. It's obvious, no? If you remove large files from a backup, everything will run faster (and Code42 does not need to add storage space so fast). More worrying is the comment earlier in the note, which states:

We have always recommended that you do not include programs or large files of your choice that they cannot back up properly.

Seriously? In fact, Code42 admits that CrashPlan may not properly back up large files? Isn't Job # 1

for any backup app?

Needless to say, Code42's announcement disturbed some users who told us about the change. TidBITS member Peter Erbland said, "It seems to be defeating the purpose of an offsite cloud backup in the event of a catastrophic data loss."

I was curious about Code42's performance requirements, but then I checked with CrashPlan competitor Backblaze (who has sponsored TidBITS lately). Yev Pusin, Backblaze Marketing Director, explained that Code42 not only made an obvious statement about smaller file sizes that improved performance for some reasons:

  • At first backup or when many data changes, large files take a long time to upload. It can of course be expected, but what people might not realize is that smaller files can be blocked from uploading during that time, so they become unprotected.
  • After the first upload, programs such as Backblaze and CrashPlan make blocking data deduplication, meaning they analyze small blocks of each file, compare them to what is already backed up, and copy only those blocks that are new or changed. Large files may not present a problem after initial backup as long as they did not change everything so much. But as Yev pointed out, the resources needed to analyze all the blocks in a multi-gigabytes file are significant. You need enough disk space to store a copy of the file, and then the backup app needs to spend much more time and CPU power analyzing all those blocks.
  • On the recovery page of the equation, if you have backed up a large VM image for months, with changes happening regularly, then you need to restore it, you want to hit another performance issue. This is because the backup app must collect all the individually backed-up blocks in the current representation of the file, and the more of them, the longer it will take the backup servers to provide the file.

For these reasons, Backblaze also excludes VM image files and other large file types (nor does it back up system files or programs), which you can see on the app's exclusion screen.

 Backblaze Exclusions screen [19659006] So what should you do if you have a large VM image file that you want to back up? In fact, I am in this particular situation, since I have Parallels Desktop set up to run a Windows app called HyTek Meet Manager to manage Finger Lakes Runners Club Slots meetings. I rarely use Meet Manager – just a day or two six times a year – but it's important that the data is backed up when I use it, so I don't need to restore a meeting database if anything happened.

With Backblaze at least, there are three solutions:

  • Share a Mac folder with Windows in the virtual machine and save all the important data in that folder. This solution, as I do, is undoubtedly the easiest and best thing to ensure that all Windows app data is backed up just like Mac app data.
  • Backup the VM image file as it exists on the drive. Although Backblaze excludes VM image file types by default, nothing prevents you from editing this exclusion list and removing the file type that matches your image file. However, it will affect performance in the ways described above.
  • Install the Windows version of Backblaze in the virtual machine and set it to back up important Windows app data. Unfortunately, this approach requires the purchase of another license for Backblaze since it believes it is running on another computer. It's not a very satisfying solution unless you work in the virtual machine all the time and have a lot of data that can't be easily stored in a shared Mac folder.

As much as it is easy to think of internet security services like being complete backups, they just aren't. There is no need to back up system files, especially since no internet security service I am aware of can perform a "bare-metal" recovery after reshaping a Mac drive.

(Interesting is the company that has the best position to supply A full backup service is Apple, since Macs already have Internet Recovery to install MacOS, and iOS devices can back up and restore from iCloud without the need for a computer with iTunes If Apple ever decides, it needs more Services revenue, everything it needs to do, Macs also come back to iCloud and sell much more iCloud storage, which would be a significant hit for existing Internet backup services.)

Although applications can usually be backed up and restored, there is a terrible amount of data to analyze, transfer and store in a situation where you can generally download again with just a few clicks. The Microsoft Office suite is 8.6 GB in itself, and the four major in Adobe Acrobat, Illustrator, InDesign and Photoshop weigh in at 5.6 GB. Apple's iWork Pages, Numbers and Keynote package is svelte compared to 1.8 GB.

But remember, an internet security service is only part of a solid backup strategy, and it should always be seen as a backup of the last resort, the one you turn to if everything else is lost. Spending some time reinstalling macOS and downloading apps is not the end of the world – losing your actual data is.

So if you use Backblaze or CrashPlan or other Internet backup service, always make sure you also have a localized backup made of something like Time Machine and a bootable duplicate created by something like SuperDuper, Carbon Copy Cloner or Chronosync. The versioned backup allows you to restore an older version of a file that was corrupted or damaged by human error and then stored, and the bootable duplicate allows you to get up and running as quickly as possible if the entire drive dies.


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