From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ryusuke Konishi Subject: Re: Number of CheckPoints Date: Thu, 30 Jul 2009 23:38:49 +0900 (JST) Message-ID: <20090730.233849.87826385.ryusuke@osrg.net> References: <4A711C80.1040500@epoch.com> Reply-To: NILFS Users mailing list Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4A711C80.1040500-ZE272gM1l1AAvxtiuMwx3w@public.gmane.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: users-bounces-JrjvKiOkagjYtjvyW6yDsg@public.gmane.org Errors-To: users-bounces-JrjvKiOkagjYtjvyW6yDsg@public.gmane.org To: users-JrjvKiOkagjYtjvyW6yDsg@public.gmane.org, dfuller-ZE272gM1l1AAvxtiuMwx3w@public.gmane.org Hi! On Wed, 29 Jul 2009 21:07:28 -0700, David Fuller wrote: > 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. 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