Number of CheckPoints

Firstly thanks to Robertas for solving my initial problem with cleanerd not running properly on Ubuntu 9.04 . Upgrading the nilfs tools worked perfectly.

I was wondering how many checkpoints are kept and for how many days? I see days worth of checkpoints going back about a week.

Regards,
--David F.

Hi!

At present, ``protection period'' is the only parameter determining the assured lifetime of checkpoints.

You can extend or shrink it by changing /etc/nilfs_cleanerd.conf conffile, and you can store checkpoints up to the capacity of your drive.

Note that a HUP signal must be sent to the cleanerd when you reflect changes on the conffile.

Or you want to know the maximum number of checkpoints ?

OK, here I show some calculation for your information:

The maximum number of checkpoints (or snapshots) is, theoretically,

2 ^ 64 - 2 = 1.84467441 .. x 10 ^ 19 (about 18.4 exa checkpoints)

In practice, maximum block count limitation will reach before this.

For example, a 32-bit Linux kernel can handle up to 2 ^ 32 blocks. Since NILFS2 stores 21 checkpoints in a standard 4KB block, 32-bit nilfs can handle up to

90,194,313,215 (= about 90.2 giga) checkpoints

If we create a checkpoint per 5 seconds, it corresponds to

18,038,862,643 seconds = 5,010,795 days = 13,728 years

So the conclusion is, you know, up to the capacity of your drive ;)

Cheers,
Ryusuke Konishi

I made a miscalculation.

90,194,313,215 checkpoints =

450,971,566,080 seconds = 125,269,879 days = 343,205 years.

In either case, the conclustion is the same.

Ryusuke