Add option to disable backup compression

Feature
21

Note to self:

Recently hit space issues again and backups failing so this post needs revisiting soon.

Note that in order to create a backup resulting in a 12GB gzip file I require ~36GB+ of space dedicated to backups, ~24GB+ of free space:

  • 12GB for the backup from the day before
  • 12GB for the new backup file
  • ~12GB+ tar archive to be compressed into gzip file (original DB file backup + original image files

So as backup sizes increase by 1GB, the backup / space requirements are actually increasing by a ~3GB.

This assumes that you are only keeping a single previous backup - where the Discourse setting maximum backups is set to 1.

The Discourse default is 5, so using defaults I would need ~84GB dedicated to backups to allow them to work.

2 Likes
22

What is the lion’s share of the backup? I assume uploaded images and so on? Wouldn’t it be easier to specify the backup is database-only, and thus make it a tiny fraction of the overall size?

(Yes, we’d still need some way to back up the images independently, but at least then the urgent need for 100GB+ of space would not be present.)

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Yes the lions share of the backup content is “uploads”.

However a backup is not complete without the “uploads”.

My personal target is to move the images / “uploads” to Amazon S3 to avoid this issue for this specific instance, however there is still some testing to be done on a high topic / post count instance before I can trust the migration to S3, some issues already highlighted in that thread (more specifically avoiding a rebake of all posts).

I have other Discourse instances that would benefit in the backups being created in a more streamlined way.

2 Likes
24

I have the same problem as this thread, I have many GB of images and while I want to migrate them to S3 from what I have read the migration script seems a bit buggy still. So, I still have images locally but am running out of disk space given the high ceiling needed to allow a backup. Even if I could delete the old backup before creating the new one it would be OK for me. In fact I have been doing that manually.

Note that the backup system also seems to be failing me on the free disk space calculation, it will fill up the whole disk before giving up, and not even delete the partial files. Then the whole computer gets unhappy. There should be a calculation to not do a backup if there is no disk space for it, taking into account the space needed for the compression etc.

Edit: I am going to run a cron job which will delete the (sole) local backup every day. That should solve my immediate problem, but I think it would also be nice to have an option to immediately delete any (local) backup that was already successfully copied to S3.

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What are the current gzip options used for the compression of the backups?

Unlike in the topic, I was interested in saving space by using a more efficient method of compression. I made some quick and dirty tests vs. our SQL dump with different gzip levels and also brotli.

2630702226 level1.sql.gz
2276305530 level1.sql.br
2216602536 level5.sql.gz
2147212204 level9.sql.gz
2036157791 level2.br
1851831279 level4.br

As we can see, Brotli level 4 destroys Gzip level 5 in terms of efficiency, while the compression time was in the same ball park. Brotli level 1 result was not bad considering it was lightning fast tool.

Anyway, I find gains of 10% or more quite interesting.

1 Like
26

Interesting, what were the actual compression times? :thinking:

27

Zopfli will be more interesting here, since it’s compatible with normal gzip uncompression tools. Brotli needs a different decompressor.

2 Likes
28

zopfli is scary slow, I doubt we would want to use this for anything like a giant backup. At least brotli is somewhat optimized for speed.

3 Likes
29

backup gzip compression level for uploads

is there a way to disable gzip compression. since my uploads are mainly already compressed images, it is a waste of resources and time trying to compress them again.

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From a related thread: