Recommended way for DB migration

[Lord_Helmchen]

Hi Mario et al.

What is the recommended way of migrating an IMatch3 DB into IMatch5? Using the DB Converter, or do an category export and import? Only categories are relevant.

I nevertheless plan to let the thumbnails to be recreated (shrink from 300x300 to 250x250 to same some DB space) and local image cash to be recreated to be future proof for 4k resolutions in future.

My old DB has about 130k of photos.

[Mario]

DB Converter.

[Lord_Helmchen]

Short and clear answer - thanks! 

[Ferdinand]

But if you want to shrink the thumb size then you will have to force a refresh all images after the conversion.  In this particular caseI think it will be faster to start from scratch and import the categories.

[Mario]

Shrinking thumbnails from 300 pixel to 250 pixel will not conserve much disk space. I would not do that, especially not with today's 100 bucks per Terrabyte hard disks. Even a very large database with several hundred thousand images fits several times on a 64 GB disk/stick/partition...

[Lord_Helmchen]

Maybe I should give it a try, but I have the feeling that in v3 since the DB file got larger than about 7 GB IMatch became pretty slow.

At least with about 170k photos and 10 GB is was slow...

[Mario]

The size of the database file on disk is not important. IMatch does not need to search the entire file for information, it's all indexed.
170,000 files is already a mid-size collection. Some of the large vendors would ask you to get a dedicated server and disk array for that 

Convert your database as-is. Use a SSD or a high-speed USB 3.0 stick to contain it for optimal performance. Run a Database > Tools > Compact & Optimize after the conversion has completed. Do some work. Post the logfile. It contains statistics which tell me how IMatch performs on your system.

[Ferdinand]

One small point. I did both - conversion and fresh start - and I found that the converted db was about 10% smaller. I suspected that 3.6 used more aggressive jpg compression, but Mario wasn't so sure.

[Mario]

IMatch 3 uses a proprietary compression schema for thumbnails (from Lead), but when it converts the database it converts the thumbnails to JPEG using the same parameters used by IMatch 5. Without a detailed analysis of the two databases used for this test, I cannot be sure. In general, IMatch does not care too much about using a couple of extra megabytes on disk. Disk space is cheap.

[Ferdinand]

The point of my comment was to warn the OP that the converted DB with 300px thumbs might actually be smaller than a fresh DB with 250px thumbs, and so he could be wasting his effort, irregardless of whether a small reduction would be worth the effort.

[Mario]

Understood.