Why is snapshot way bigger than disk usage?

April 17, 2016 1.5k views
Backups Ubuntu

I have 80GB droplet, the disk usage is about 11 GB, yet the snapshot is almost 32 GB and takes very long to create. Why is the snapshot using so much data?

9 Answers

Hi all,

I asked to DigitalOcean support, and I got this answer:

"At this time, our snapshot tool shows the additive space used, so when you add something to the droplet it adds onto the snapshot size, but when you delete it, it stays in the snapshot size. Our engineering team is working to correct this number displayed before we begin charging for snapshots!"

So it seems it is a bug and it will be corrected soon.

Best Regards.

  • Thanks for sharing what's up! I was wondering why my droplet was using 20.97GB for a snapshot despite having disk usage nowhere near that and using just 6.84GB last month.

Well, now they are charging 0.05$ per month per GB...

I still don't quite get why snapshots gets so big. For example I have two identical droplets, 20GB each. Both of them uses about 3GB of storage. Snapshot of the first one is 3.15GB and thats ok. But snapshot of the second one is 16GB!

  • Same issue here!

    Using about 3 GB only while Snapshots are ~16 GB in size!

    Now that they are charging for it it's becoming really insane!

Because the Snapshot has to store 80GB of Data (including all the empty space) and while Compression could probably get that smaller, the higher the compression factor, the more CPU intensive decompression is, so they probably choose a mid-point between size and speed.

  • Hmmm. I notice that snapshots grew in size despite me not getting more data on the droplet (and in the last case actually after removing a lot of data the size did not change). I wonder if they are recording disk space "as is" so they store ones and zeros that are recorded in the "empty" space as they are. That would make sense.

    • I don't quite follow what you mean; it seems I have a number of snapshots with various sizes despite the filesystem supposedly being constant size. Recently I took a snapshot that was ~30% larger than the entire root filesystem size, despite other snapshots being much smaller than the total filesystem size.

Same here, it just gets bigger and bigger, at least they aren't charging

Same here. What's bizarre: There are 2yr old snapshots which are just about 1/10 of the size of my current ones. Whereas the actual net disk usage didn't change much, according to ncdu.

Same here. My first snapshot of the droplet had about 2Gb, and the last one has 19Gb. There weren't significant changes in disk usage of my droplet between them. Quite strange :-)

Same issue here.

Snapshot size is continually growing but disk used on the server has not changed.

Does anyone have an idea of what the problem could be?

It all started when Live snapshot was implemented.
I have no doubt that there is some issue during that process.

  • No, I'm pretty sure that it started long before the Live Snapshot feature was implemented.

    It's even more important now that this is resolved, since they plan to start charging for snapshot storage space.

Appears to be fixed now on my end!

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