From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Sandeen Subject: Re: ext4 blocksize peculiarities Date: Fri, 24 Sep 2010 23:57:53 -0500 Message-ID: <4C9D8151.7090800@redhat.com> References: <4C9D640E.5020609@sm-wg.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: linux-ext4@vger.kernel.org To: Bernhard Rohrer Return-path: Received: from mx1.redhat.com ([209.132.183.28]:31976 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751910Ab0IYE6f (ORCPT ); Sat, 25 Sep 2010 00:58:35 -0400 In-Reply-To: <4C9D640E.5020609@sm-wg.net> Sender: linux-ext4-owner@vger.kernel.org List-ID: Bernhard Rohrer wrote: > Hi all > > I have a 3.3 TB partition (yes really) that is formatted with ext4 and 4 > kiB blocks. What little data I have on that appears to use up an > extraordinary amount of space, so I had a closer look. > > root@newcollab:/home/adminlion# df -h > Filesystem Size Used Avail Use% Mounted on > /dev/mapper/primary_vg-primary_var > 3.5T 43G 3.3T 2% /var > > we see that 43 GiB appear to be taking up something that gets rounded to > 200 GiB by default 5% is reserved for the super-user, 5% of 3.3T is 168G, 168G + 43G is roughly 200G -Eric > if we look at: > > root@newcollab:/home/adminlion# df > Filesystem 1K-blocks Used Available Use% Mounted on > /dev/mapper/primary_vg-primary_var > 3696706360 44362800 3464561624 2% /var > > now 44362800 4k blocks are 169.23 GiB, those are 1k blocks :) Anyway, what you are seeing is the 5% reserved space, which does not show up in "Used" but is reflected in "Avail" It is confusing and you're not the first one to get tripped up :) -Eric > which does indeed round to 200 > GiB. similar usage also gets reported when I get the properties of the > share via cifs. > > debugfs shows: > > Block count: 937689088 > Reserved block count: 46884454 > Free blocks: 912175341 > > so while df shows 4 times as many available 1k blocks as debugfs, which > after all shows the actual number of 4k blocks, both are more or less in > agreement as to the space used. This leads me to believe that somehow > only 1k of every 4k block gets used. Now i could of course reformat to > 1k blocks, but I'd prefer to avoid that. > > OS is Lucid64 and the volume is a LVM volume. > > Has anybody seen this before? Uncle Google was rather mum on the subject. > > cheers > > Bernhard > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html