I have a rooted Android phone that is no longer in use. I have currently been using Linux Deploy on an Android tablet to run a Debian installation in chroot, and have found it so useful that this (very cheap low end) Android tablet has replaced a laptop. From this experience I am wondering if I could use a similar installation on the old phone as a NAS / VPN at home. For some reason, the Debian install running on the tablet does not seem to be stopped / offloaded by the Android OS - i.e. I can SSH in at any time, even 10 hours after use, and it still responds.
I could of course purchase a Raspberry Pi or similar device. However, I live in a smaller city in India, which means this proposal has two disadvantages - 1) unlike a phone, the Pi has no protection against the frequent one or two hour power cuts that take place here (a UPS would not last long enough) and 2) the cost of a Raspberry Pi in Indian rupees is not expensive, but high enough that it's not something I can simply spend on without thinking.
So, what would be the disadvantages of using an Android phone as, effectively, an ARM-based Linux computer?
I am aware of this question but neither the question nor the answer seems specific enough for this purpose.
NB: By a NAS I don't mean a device to which I could attach external storage - the storage in a microSD card in the phone should be plenty.