I was wondering if various storage virtualization methods can be classified into virtualization at the device (disk), partition or filesystem levels, as following
- RAID belongs to virtualization at the device/disk level, which replace physical disks with logical/virtual disks.
- LVM belongs to virtualization at the partition level, which replaces partitions with logical/virtual partitionss (also called logical volumes).
- There is also vitualization at the filesystem level, which replaces filesystems with logical/virtual filesystems, for example, Network-attached storage (NAS).
If my above understanding is correct, does virtualization at each level also implement virtualization at all lower levels? For example, virtualization at partition level also implements virtualization at device level, and virtualization at filesystem level also implements virtualization at both partition and device levels?
How do different levels of virtualization affect/determine their different areas of applications? For example, are there applications suitable for RAID but not for LVM, and for LVM but not for RAID?
There is a Wikipedia article for storage virtualization, where there are two main categories of methods, block virtualization (which can further be classified into storage device-based and host-based and network-based) and file virtualization.
Compare the article with my understanding in part 1,:
- Is it correct that storage device-based block virtualization is same as virtualization at the device level. Host-based block Virtualization is same as virtualization at the partition level. File virtualization is same as virtualization at the filesystem level.
- But in Host-based block Virtualization#Specific_examples, it looks like Host-based block Virtualization includes virtualization at the filesystem level? How shall one understand what is File virtualization then?
- I would rather to single out network-based from block virtualization in the aforementioned Wikipedia article, because for storage virtualization over network, I think we can also classify the various methods into the levels of device, partition and filesystem? For example, can I say Storage Area Network (SAN) belongs to the level of device, and Network-attached storage (NAS) to the level of filesystem?
Thanks and regards!