The answer to this question depends on what you mean by totally different. Yes you can have varying styles of hard drives in a single computer, however you are of course limited by what your motherboard and operating system can handle.
There are many different computer magazines that rate the top external hard drives. Magazines such as CIO insight and Computer Edge. Both are extremely credible.
In the computer's HARD
No, cellular phones do not contain hard drives. They do have internal memory but they have a different type of setup than a computer. Some cellphones even take memory cards.
It's called a "raid" disk controller. Using a raid controller you can connect 2 or more hard drives in a number of different configurations; one being that the drives are "mirrored".
The most common problem with large hard drives is computer crashes.
Viglen is the maker of several different products. All their products are computer based. They make hard drives for a desktop computer, different sized towers from small to tall. They also make server drives for large companies.
Assuming that when you say system unit of a computer you mean the computer case A.K.A. the tower, then no, hard drives are not always installed internally. Hard drives can be in external enclosures, hard drive docks, and even network attached devices.
The best place to visit about purchasing computer hard drives is an online website. A person can go on Amazon, Ebay, Newegg, or Bestbuy website to find the best place to visit about purchasing computer hard drives.
hard drives
recycle,destroy, or burn it completely. Destroy the hard drives with a hammer.
The space inside the computer for DVD/CD/Floppy(who uses these anymore?) Drives and also Solid State Drives (SSD) and Hard Drives.
No. An external hard drive doesn't have ram in it. It only has storage space. Ram is a special chip that goes inside slots inside your computer. Each computer uses different ram.