Question

1. How does volume management relate to file systems?
2. While flash storage is now often used as a hard drive replacement, full use of flash arguably will require a major shift in how operating systems work. Why?

Answer 1

Volume management was developed in the late 1980s to enable the creation and management of file systems larger than a single disk, which offered the possibility for greatly improved performance. Since almost all file systems at that time could only create a file system on a single device, volume mangers provided file systems a single set address range for multiple devices. Other volume manager enhancements in the 1990s included support for software RAID 1 and 5.

The purpose of file systems is to maintain a consistent view of storage so that we can effectively manage it. This is done in a way that allows the users to create files and directories as well as delete, open, close, read, write and/or extend the files on the device(s). File systems also maintain security over the files that they maintain and, in most cases, access control lists for a file.

There are a few reasons RAM is not used that way:

1. Common desktop (DDR3) RAM is cheap, but not quite that cheap. Especially if you want to buy relatively large DIMMs.
2. RAM loses its contents when powered off. Thus you would need to reload the content at boot time. Say you use a SSD sized RAMDISK of 100GB, that means about two minutes delay while 100GB are copied from the disk.
3. RAM uses more power (say 2–3 Watt per DIMM, about the same as an idle SSD).
4. To use so much RAM, your motherboard will need a lot of DIMM sockets and the traces to them. Usually this is limited to six or less. (More board space means more costs, thus higher prices.)
5. Lastly, you will also need RAM to run your programs in, so you will need the normal RAM size to work in (e.g. 18GiB, and enough to store the data you expect to use).