Are there any particular advantages/disadvantages to storing apps on the external storage of an Android device? As I have a Nexus S, I can't think of advantages for me as I can't remove the storage, also the internal storage is more than enough for my needs.
I noticed that on phone start up, when I had all my apps moved to USB storage it was quite sluggish to register all the apps on the menu/home screens.
I also read somewhere that having a wallpaper set from a photo that was stored on the external memory actually drained quite a bit of battery too with all the reads (although I think this may have been a bug).
For newer devices with gigabytes of internal memory moving apps to external storage is not necessary, since space is not an issue. However for handsets with low memory it's an invaluable tool that extends their shelf life for their owners.
taken straight from android developer site
Also -> Applications That Should NOT Install on External Storage (more details on android developer site)
Widgets won't work if they're on the SD card.
Applications installed on SD card cannot run if you remove your SD card or you're turning on USB Mass storage (so it can be accessed from a computer). That's the only drawback I have been experiencing.
I've actually seen performance improvement since moving to SD; before I moved to SD I had exhausted the internal memory (about a few kilobytes left) and the phone lags quite badly. Since moving to SD (and therefore freeing some space in the internal memory), and the lag disappears.
For some phones and devices (especially the older ones) the internal storage is quite limited. Every application (and it's data files) take precious space. I.e. my Ideos has 512MB and was nearly full before I started "evacuating" apps to the SD card.
Another factor is the ability to backup your apps and data, or move them to another device.
Other than that, you are right in your observation that apps load slower from the external storage compared to the internal storage. This is very visible if you have those apps' shortcuts on your home screen - you'll see a generic Android icon for the first 30 seconds until the app is located on the card.
I found that switching to a class 6 microSD (I had the default class 2 that came with the phone) improved the situation considerably. Still, it takes my phone about 20 seconds to "equalize" following a cold start.
Security and Performance Implications
The application resources stored on external storage are read-only and hence there are no performance issues with loading or launching applications on SD card.
The post is written by a 'Suchi Amalapurapu, an engineer who worked on this feature.' The feature being the ability to put apps onto the SD card.
In my experience there has been little or any perceptible performance problem. I was having a really annoying experience managing my memory with my Nexus One. I used S2E to migrate and have not looked back. Amazing to be able to not have to delete apps just to install new ones.
I think that moving apps from internal to external does not affect the performance.
But it does add on an extra few milliseconds to open the app from external storage instead of in internal storage. mileage will vary from device to device, depending on speed, Android version etc
Apps that have a service that is constantly open, like for example Viber, WhatsApp, Facebook messenger, etcetera can slow down the ui a lot if there are a lot of these running, so its preferable to keep apps with a constant service on the phone memory, since the impact there is non noticeable by comparison.
Never ever move your apps into your external SD card. It will make your phone to lag more and the phone will reboot more slowly than usual. You might even have to restart the phone daily or once per week. It will take longer to process all the information that those apps have. I speak from experience.