Disk block changes following a save
Posted on 2006-11-08
I'm not sure if this is more of an application specific question, but I'll try here first...
Let's say I have an MS Word document sitting on a disk, and it's currently occupying 10 physical blocks on the disk. I then open the document and make a one word change to it, and click Save. Can anyone tell me which of the following occurs:
1) The physical block on the disk containing the portion of the document that was changed is updated with the new data, and presumbably has a timestamp updated to show the time of its last change. All other physical blocks containing data related to the document remain unchanged.
2) The entire document is written back to the disk. The physical blocks may remain the same, or may change depending on various factors determined by the operating system.
The reason I need to know this is that I'm currently involved in the design of a very large system which will have a lot of data replicated across a WAN. The replication is block-based, so I'm trying to find out how common applications like MS Word save their files.
Many thanks for all your help