■ Cloud drives supporting files on demand

From the early days of RapidShare and filehosting, through to pricey Amazon S3, we have happily arrived at the era of cloud storage for everyone. Whether it is for file sharing, document backup, ransomware protection (file versions) or syncing all your files so you can work from any device, cloud storage has many practical uses. There are tons of cloud backup providers (free or paid), many offering a generous amount of free storage, including Microsoft's OneDrive which is preinstalled on all Windows 10 computers.

Many old timers can't help feeling this whole cloud thing is a fad, that adds little to what can be done simply with an external USB hard disk, as we used to backup things until yesteryear. Even if you don't care about the security of your data trusted to some cloud company "for free", what if said cloud company you use to host your files goes under? What then with your lifetime memories? But I digress. Let's assume that cloud storage is good and concentrate on the subject of using cloud drives.

Cloud storage is split in 3 major types:

Old school filehosting. File sharing services of yore like Mediafire, Jumpshare etc are still around, for temporary free file hosting. Illegal downloading is on the wane for some years, so many of these guys are rebranding for cloud storage (e.g. Mega.nz offer a cloud drive for backup)
Backup and reliability. Companies (Egnyte, Backblaze etc) that provide automatic and continuous backup of your local documents, usually targeting the enterprise (i.e. not free). If I were an IT administrator for a large company I would have cold sweats about the "industrial strength encryption" professed — but that's only untrusty old me :)
Cloud drives. Think of a folder that resides somewhere up there on the clouds, but looks and behaves like a local folder on your hard disk so e.g. you can share your work with colleagues and work seamlessly from a number of your own computers. This is the most interesting case I will be investigating.

These distinctions are not clear-cut, there are many hybrid services that combine points 1-3. From those that offer cloud drives, there are 2 varieties, those that basically mirror the cloud and local files (the same files are stored online and "offline" on your computer), and those that offer cloud-only storage avoiding this duplication. This is a smart feature that saves space, especially if you work on many computers and you don't need all the files present locally at all times. This feature is called files on demand in OneDrive, smart sync in Dropbox and all sorts of other funny names like Google drive's File Stream.

Since version 4.2 xplorer² is careful with cloud-only files, and doesn't unnecessarily start a download from cloud to local storage, unless you want to open or copy the file (document, picture, video etc). Usually cloud-only files have a different icon overlay, and special file attributes like O (online); also the Availability status column goes from Available offline to online only for cloud files:

The down-side is that without an internet connection you cannot open such files.

Unfortunately some cloud drives don't give special file attributes to online-only files, so xplorer² cannot know which files are local and which require a download. The table below lists the most popular cloud drives that offer some free storage, and indicates which work best with xplorer² in terms of files on demand (green tick ):

Cloud Service	Free storage	Files on demand	notes
OneDrive	5 GB		comes installed with windows 10
Dropbox	2 GB		smart sync for paid plans only
Google drive	15 GB		Drive file stream only for paid gSuite accounts
Box drive	10 GB
pCloud drive	10 GB		no indication of cloud-only files
sync.com	5 GB	—	mirrored files, all available locally
Degoo	100 GB	—	more of a folder backup than cloud drive

Table 1. Most popular cloud drives with free online storage

xplorer² was tested and works ok with all these cloud drives. You can manage files just like as if they were locally available in your hard disk, and changes are mirrored in the cloud storage. For example you can create new files inside a cloud drive and they will be automatically uploaded. You can rename, copy even delete files.

When deleting files in cloud folders, keep in mind that they won't go in the recycle bin, and they will be also removed from the "cloud". However all services offer an online recycle bin (available through the web interface), which can be used to undo accidental deletions.

When xplorer² can detect cloud-only files, it is careful to avoid downloads for simple browsing and preview. It will only show information that is available like simple file sizes and dates. Other more complex properties (e.g. picture Date taken detail) will remain empty. You can search for filenames in cloud folders as usual, but searching in file contents for text is only for locally available cloud files.

There is a special advanced option that instructs xplorer² to treat cloud-only files as normal files, which will allow you to search inside them for text, but that's going to download every file in your cloud collection, which may not be what you want. You may be better off using the web interface's search box (through your internet browser)

Each cloud storage provider has its own way to send files to the cloud, releasing local hard disk space. For example within OneDrive, you right click on the files you want to be cloud-only and use Free up space command from the context menu. Let's hope that more cloud drive providers will start using the Offline file attribute to declare cloud-only files for optimal performance in xplorer².