Disk partition

You will just be able to restore to the system partition without it touching your 'archive' partition.

However, if possible use time machine backups. Always better to have a backup of files and not need it.

"Do i have to format only system partition or do i have to format the whole hard disk?"

You would only have to re-initialize the "boot partition". No need to re-initialize and re-partition the entire drive.

As mentioned in reply #2, you should consider some kind of external backup.

I DO NOT recommend using Time Machine, however.

Instead, get an external drive with an overall capacity larger than the total of your internal (that is, 250gb or larger).

Then, partition it, just as you did your internal drive.

Next, download CarbonCopyCloner (or Superduper). You can get CCC here:
http://www.bombich.com/download.html

Now, use CCC to "clone" your internal boot partition (to your EXTERNAL boot partition) and then your internal data patition (to your EXTERNAL data partition).

Do this, and you will be fully protected against a failure of the internal drive.

A CCC backup is BOOTABLE and is also in POFF (plain ol' finder format) -- just mount it and "go". You CAN'T BOOT from a T.M. backup.

You can either buy an external drive, but I actually suggest you purchase the drive "core" and enclosure separately, and build it yourself. It's easy to do, and since you put it together, if anything ever goes wrong with it, you'll know how to take it apart.

I suggest this as an enclosure:
http://oyendigital.com/hard-drives/store/U32-M.html

Then find a 2.5" drive to go inside...

Vairamuthu said:

I partitioned 150GB for system and 100GB for data and stored all data's.
If my OS get corrupted and i want to install a fresh copy of ML.
Do i have to format only system partition or do i have to format the whole hard disk?

Click to expand...

Several points worth raising here:
1. OS X rarely gets "corrupted". In ten years of using OS X (10.2 to 10.8), I've reinstalled the OS twice. Most problems are caused by third-party software or problems in the user account.

2. By default, a reinstall of OS X will replace the existing System files and leave your user data, apps and settings in place. So even if something goes wrong, there is no need to separate your files from the system (any more than the standard "user domain" is separate from the system).

3. You don't need to re-format either -- perhaps erase and install, but not re-format.

4. OS X expects to find stuff in particular places, and attempts to alter those locations can cause trouble.

5. I've never partitioned a drive and not wanted it to be different later.

Time Machine is excellent for data backing -- I see no reason not to recommend it. But CCC is ideal for making bootable clone images.

Vairamuthu said:

I partitioned my 256GB in to 150 and 100GB. How can i make it as one single disk?

I felt my mac is getting slower when it was a single disk. Apps took long to start and had system freeze issue while startup.

After partition i am feeling its back to normal and no more freeze during the start up.

Click to expand...

Use Disk Utility to create one partition.

Whatever your problem was, I suspect that partitioning the drive was coincidental, rather than the solution to the problem. It may have been as simple as rebooting that was the fix.