06 Apr 2016, 00:37
This is mainly related to resized images, and yes, you can expect the cache to be fairly large because of this. However, 1GB does sound like a lot compared to your main site content at 600MB. Essentially, I do not see a problem with this ... It does not slow down anything, and most professional hosts offer 100GB for $3 ... many hosts offer "unlimited" storage now ...
If you rename/move a lot of folders- or files in your content, you will get a lot of stale (unused) files in your image cache. This is because the cached image is based on a request path, which changes whenever you change a folder name that is in the path of the image. Unlike pages/templates, X3 cannot clean up image-cache, because they are based on url-requests. Once in a while, you can delete all files inside in the _cache/images/requests/ and _cache/images/rendered/ folders ... That will require the cache to be recreated (requires a lot of processing), but it means you have deleted all unused files. This is not really necessary, but if you know that you have renamed a lot of folders and/or moved folders around when creating the website, then you have a lot of unused resized images in the cache.
In your website.com/?diagnostics, are you sure open_basedir is disabled? If open_basedir restriction is enabled, it would prevent X3 from being able to clean up the cache folders.