Will FileVault affect data saved in Cloud services?

File Vault full disk encryption won't have any effect on your cloud services. When you login the disk is decrypted this means any cloud services can access the same data as you - in it's decrypted form. The documents uploaded will not be encrypted (unless the service does it's own encryption too).

See the providers for more detail. iCloud has this info…

iCloud security and privacy overview - Apple Support

You can encrypt files before you upload them to any cloud services - but that is separate to File Vault.

File Vault has a few potential disadvantages…

If the disk fails recovering data is harder because the data is encrypted - Make good backups & test them!

The computer is decrypting data 'on the fly' that means it is doing more work than a system without encryption. The performance difference is probably not noticeable with newer Macs unless you start using benchmark tools.

Forgetting/ losing the password & recovery key will render the data inaccessible!

The advantage is obvious, your files are not accessible to anyone unless they have the password (or they access the device when you have logged in). Normally the files on a Mac can be read if someone has the know how to access the disk, that info is available all over the internet 🙂

e.g. OS X Mountain Lion: Transfer files between two computers using target disk mode

It really depends if you need to protect your data 'at rest' (when the device is powered off). File Vault will not protect you from any malware or other bad software etc. This is because the OS is effectively the same when in use - once the data is decrypted it is accessible, which is why File Vault likes you to lock the screen with a screen saver password.

See the File Vault info if you haven't already done so…

Use FileVault to encrypt the startup disk on your Mac - Apple Support

I'm not familiar with Boxcryptor but it may be an option (there are probably others too).

Another option is to use an encrypted disk image…

How to create a password-protected (encrypted) disk image - Apple Support

That uses the same principle as File Vault, but can contain a limited set of data. It really depends on how practical it is for you to store data inside a mounted disk image. For some data is impractical (like settings that are loaded on login), but keeping notes or other data it can be a good solution.

The same rule applies - once decrypted & accessible (when the volume is mounted) anyone can read it on that Mac, but the encrypted container is not readable without the password. The container would be synced online, not the mounted volume. Since the online service sees it as 'one big file' be careful with the size of the disk image.

FWIW: You can have encrypted disk images stored on a disk that has File Vault encryption enabled, but keeping track of which password is for which one can be a job in itself 🙂

Hope that is clear, it can get very meta if you aren't careful.

iCloud data is encrypted everywhere in the chain.

Google says it is stored in "secure data centers," which may mean it is encrypted, except Google uses your personal information to sell ads. But, they claim they won't use your "Private documents" in marketing.

Dropbox states your files are encrypted when "at rest," but says it will give it up to anyone with a warrant.

Apple claims it will not release encryption keys to any third parties.

iCloud security and privacy overview - Apple Support

https://www.dropbox.com/help/27

https://support.google.com/drive/answer/141702?hl=en

https://support.google.com/drive/answer/2733115?hl=en&ref_topic=2428743

https://www.google.com/policies/privacy/