[Galaxy S II General] LightspeedGalaxy:
Well, now you have a phone that doesn´t hide everything from the user it shouldn´t be that hard to make a backup.

There are basically 4 interesting partitions on the phone:

system (about 500MB) - This holds more or less the whole Firmware. While it is technically just a partition on the flash-memory, it is used like a ROM in normal usage, so the only situation where something will be written on this partition is a firmware-upgrade.

data (about 2GB)- This partition holds all user-installed apps and their settings.

sdcard (about 12GB) - This is not really a sdcard. Instead it is a part of the internal memory, you can use it for example for media, documents, images etc., whatever you like. This partition can be accessed on your computer as a regular USB-storage, and you can do a backup of it the way you like, either simply copying everything, or using a backup-solution of your choice.

external_sd (optional) - This is the micro-sd-card you can put in your phone. Obviously you can use it for anything you like. This partition is also accessible as a USB-storage or you can use a simple USB card-reader to access it on your computer.

Usually all your applications and settings will be stored in the /data/-partition.

If you choose the Move-to-SD option in the application-manager, some parts of the application will be moved to the (internal) /sdcard/-partition, but all the user-data/settings still remain on the /data/-partition.

So the maximum space you need to backup all your settings and apps is under 3GB.

Now to the possibilities of a backup, and the importance of the different things.

A nandroid-backup will basically make an image of the /system/ and /data/ partitions (also a bit more, but that´s not really important).

Usually it will use the /sdcard/-partition, which actually is still in your phone.

If you restore a Nandroid-Backup your System will be in the exact state before the backup, including all applications with their settings (which also means contacts, e-mails, sms etc).

Obviously everything that has changed after the backup will be lost.

A restore well also restore the complete firmware from the backup.

A backup from Nandroid can only be restored on the same phone, with the same partitions.

The second possibility to make backups would be TitaniumBackup.

This program will store all your installed applications and their data.

Default it will store it on the internal /sdcard/, but it is probably more useful to change the path to the external_sd.

Everything in Android is an application, so this will also save all your settings.

During a restore TitaniumBackup simply reinstalls your applications and then restores their settings.

TitaniumBackup can restore your applications with any Firmware, and in theory even on other phones (it may not work with special System-apps but it surely works with most "user-apps")

So Clockworkmod is great if you want to play around with different firmwares, especially Custom ROMs.

You can install different ROMs, make a backup and very easy and fast switch between them.

For a "regular" backup TitaniumBackup is maybe the better choice, it can backup all your settings and applications and for example if a Firmware-update goes wrong simply restore anything.

There is no real need to backup the /system/-partition anyway, you can simply download the Firmware and flash it, there is no user-data on this partition.

sdcard and external_sd usually only contains media, which you probably have somewhere on your PC anyway, so there is no real need for a backup, maybe for the pictures and videos you make with your phone, but again you should copy this on your PC regularly anyway. And if you want you can easily copy everything on it as well.

Question is if I have my phone filled with games, different apps which make let's say 10 gb (not that much counting in that one game may be up to 1 gb), so how do i backup this? To SD card?[/quote]

Apps can´t be several GB in size on Android. Normally you have only around 2GB for Apps, if you use the App2SD-feature it can be expanded a bit.

If applications need a lot of data, for example like navigation-programs or games, they will download this on the first start and store this on the /sdcard/-partition.

As I said, you can access this easily like a removable drive and copy everything you like.

It isn´t also that important to make a backup of this, as it can be downloaded again anytime, and if something goes wrong it usually will mess up your system and don´t influence the data-partition anyway (well as long as you don´t repartition the whole memory)