From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: util-linux-owner@vger.kernel.org Received: from smtp209.alice.it ([82.57.200.105]:39132 "EHLO smtp209.alice.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753058Ab3AGSeD (ORCPT ); Mon, 7 Jan 2013 13:34:03 -0500 Message-ID: <50EB14FB.3080002@tiscalinet.it> Date: Mon, 07 Jan 2013 19:33:31 +0100 From: Goffredo Baroncelli Reply-To: kreijack@inwind.it MIME-Version: 1.0 To: Hugo Mills , dsterba@suse.cz, util-linux@vger.kernel.org, linux-btrfs , Chris Mason , Chris Murphy Subject: Re: Btrfs: wipe all the superblock [redhat bugzilla 889888] References: <50E9C267.3050302@inwind.it> <20130107163327.GK20089@twin.jikos.cz> <50EB11E0.8030403@tiscalinet.it> <20130107182426.GM19051@carfax.org.uk> In-Reply-To: <20130107182426.GM19051@carfax.org.uk> Content-Type: text/plain; charset=ISO-8859-1 Sender: util-linux-owner@vger.kernel.org List-ID: Hi hugo On 01/07/2013 07:24 PM, Hugo Mills wrote: [...] >> print "Superblock #%d - %20d - '%s'"%(i,pos,sign) >> >> $ python extract-sign.py >> Superblock #0 - 65600 - '_BHRfS_M' > > 64 KiB OK, (above) > >> Superblock #1 - 67108928 - '_BHRfS_M' > > 256 MiB .... above is 64M, below is 256M ! > >> Superblock #2 - 274877907008 - '_BHRfS_M' > > 1 TiB > >> Superblock #3 - 1125899906842688 - '' > > 4 PiB > >> Superblock #4 - 4611686018427387968 - '' > > 16 EiB Not reachable in linux. There is a VFS limits to 8EB. > > >> To me it seems that in a 7TB filesystem there is only 3 superblocks. > > That would be as expected. How many on a 5 PiB filesystem, though? > Or a 20 EiB one? I wrote 7TB, but I meant 8EB. I first tried a test with 7TB and I wrote the email, but then I retested with 8EB and I corrected the email, forgetting some 7t instead of 8e... Anyway, if BTRFS would allow more than three super-block, in the 7TB case, the super-block at 1TB would appeared > > Hugo. > -- gpg @keyserver.linux.it: Goffredo Baroncelli (kreijackATinwind.it> Key fingerprint BBF5 1610 0B64 DAC6 5F7D 17B2 0EDA 9B37 8B82 E0B5