Magento – Catalog Product Media Cache 44 gb

Under System -> Configuration -> System you'll find a setting which dictates the frequency of the cron schedule generation. When the cron schedule is generated, the time stamp is stored in a cache record outside the scope of any defined cache tags, meaning it is not gotten rid of unless the storage is flushed vs flushing the tagged cache records. The time stamp in this cache record is checked on each run to determine if enough time has elapsed for a schedule generation to run.

So in short: it's working as intended. :)

The reason the cron schedule is not calculated on each execution cycle is for performance reasons. It's far less computationally expensive to dump a precalculated schedule into the cron_schedule table and execute based on what is is found in there on each run. This same table is consequently also used for placing a lock on each job.

If you are needing to refresh the conversion rates manually, you can do it from the currency rates management page on the click of a button. If you are just wanting to effect a change in the timing of the refresh, change the setting and check back later, it will be picked up the next time the cron schedule is generated prior to the set time. Or just flush the cache storage to see it take effect immediately... ;)

Flush and refresh: Refreshing means that it cleans up alle the invalidated cache keys. for example: when you save a widget while the cache is active you get a message that the cache is invalid. In this instance you don't need to flush the cache, just refresh it. Flushing means that it throws all the cache away, it will rebuild everything from scratch.

CSS/Javascript cache: This cache is separate from the default cache. The normal cache will store in a cache-backend. That can be the var/cache/ folder, it can be memcache or redis, etc. The CSS/JS cache is stored in the media/css and media/js folders (you can thus safely delete those folders at will). Flushing browser cache is a good idea, certainly if cache headers are set up. You can also auto-version your css/js files to fix this: https://github.com/fbrnc/Aoe_JsCssTstamp

Flush Cache Storage/Flush Magento Cache: If you flush the magento cache storage it will flush all the cache options that are mentioned in the cache-table. If you flush the cache storage, everything is flushed. By default there is some database caching used by Zend that only get flushed this way.

Deleting contents of /var/cache and /var/sessions: When deleting var/cache everything is flushed except css/js (those are in the media folder). To remove sessions you need to delete the var/sessions folder (you can also store sessions in the database or redis/memcache), but you'll rarely have to. Doing this on a live server may cause problems (carts get lost).