Monday, September 10, 2018

gbak -b -e. Compress or not to compress.

Normal backup (gbak -b) by default compresses data. What the compression is, I don't know, don't care, maybe will ask developers about it.
But, gbak have -e option, which turns compression off.

So, I decided to check how it will affect backup, and is there any reason to use it.

I took TPC-R database, 30 gigabytes size, Firebird 3.0.3, and made backup several times to another physical disk (to speedup backup).
Result - option -e makes backup 7.5-7.9% faster. For 18-minutes backup it means 1 minute less.
If backup time is around 10 hours, option -e will save  ~46 minutes. This is good, but also means that you can not pay attention to "use or not to use -e", if your backup time is near 2 hours.

Everything looks good until you will check backup size. Normal backup (with default comptession) of this database have 21 gigabytes size. But -e option produces 34 gigabytes backup file!
This is 30% bigger than normal backup, and 10% bigger than database itself.

So, small benefit in backup speed turns to huge growth of backup size.
Therefore, decide for youself, use -e, or not.

p.s. time difference may depend on your hardware, backup size may differ depending on your data.

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