dividing you HDD into many partitions would affect your performance?
Yes, it would. Depending on the location of the partitions. Partitions located at the beginning of the drive (outer edge of platters) will have faster sequential read and write speed than partitions at the end of the drive (inner edge of platters). 512K random ops are marginally faster on the beginning of drive. 4K random ops are marginally faster on the inside of the drive.
Here are some pictures as an example.
Partition layout
R benchmarked
P benchmarked
I repeated these several times and they came around these numbers, give it or take 2 MB/s for sequential.
I've never tested it, but from what I hear there is little effect on performance.
The more important issue is that there typically isn't any advantage to using more than 2 or 3. I've seen people on this forum with a dozen or more partitions when they could have just used a folder structure on one partition. It just chops up the drive so that you run out of space on one or more partitions---usually sooner than you expected. It's not efficient in that way.
Its mostly for control, prevent constant extensive fragmentation and more controlled partition backups rather than file backups. Efficiency is up to the user, the partitions can be extended at any time.
Although "dozen" partitions sounds quite high. I usually have two or three, or one which doesn't occupy the entire drive, rather, I extend it as I need it. No need to have the heads roam around 2 terabytes of space, instead, they can roam around 500 gb. It allows you to arrange data by "usage". You can archive data at the end of the drive, but keep your usual stuff at the beginning. E.g: versioning at the end, your stuff at the beginning. Things you never use at the end, stuff you constantly use at the beginning. Confinement, limits and proper distribution. It's more efficient than having 2 terabytes all mixed up if done right.
When it comes to backing up/moving data, some people prefer that setup better. You can take a partition level backups of your usual stuff and leave your never-used stuff behind. It depends on the person, their usage and preference. I prefer partition level backups over file backups. You could also cross backup data among drives for redundancy. 2 drives, you can have two separate partitions A1,A2 and B1,B2 of two unrelated data. One for the actual data, other for the backup (archiving) of the other drive, i.e B1 is backed up to A2 and A1 is backed up to B2. Really, it depends on the person. It lets you have data versioning among different drives, whether its setup as raid or not.
Hard drives are too cheap, it makes it easy to buy terabytes of data without really needing all of it. Specially when the difference between 500gb and 1tb is a couple dollars, and the difference between 1tb and 2tb is also a no brainer.
