From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com (ext-mx07.extmail.prod.ext.phx2.redhat.com [10.5.110.31]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t91GGBL2025669 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO) for ; Thu, 1 Oct 2015 12:16:11 -0400 Received: from mail-la0-f46.google.com (mail-la0-f46.google.com [209.85.215.46]) by mx1.redhat.com (Postfix) with ESMTPS id 40B08C0A148E for ; Thu, 1 Oct 2015 16:16:08 +0000 (UTC) Received: by lahh2 with SMTP id h2so77943444lah.0 for ; Thu, 01 Oct 2015 09:16:07 -0700 (PDT) Received: from [192.168.43.226] ([78.25.121.70]) by smtp.gmail.com with ESMTPSA id j189sm747961lfg.48.2015.10.01.09.10.36 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 01 Oct 2015 09:10:37 -0700 (PDT) References: <560BFF8B.7030006@koolin.ru> <560D1857.9070909@redhat.com> From: Timofey Koolin Message-ID: <560D5AFA.5000500@koolin.ru> Date: Thu, 1 Oct 2015 19:10:34 +0300 MIME-Version: 1.0 In-Reply-To: <560D1857.9070909@redhat.com> Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] Usable space in PV Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: LVM general discussion and development Task - problem. I make universal extender of filesystem (for example extend fs in virtual computer after resize disk or add space to filesystem in hosting server, etc.). Before extend volume group and filesystem I want to make plan of extends. For plan I need to know how many bytes it can add to VG from disk/partition. I know size of disk, partition, free space - and I have to know free space after create PV on free space of disk. I don't know how many LV will be on target system (system, which run fsextender), I don't know fragmentation of it and etc. Is any way to know how many space take metadata and how many space will be usable? On 01.10.2015 14:26, Zdenek Kabelac wrote: > Dne 30.9.2015 v 17:28 Timofey Koolin napsal(a): >> Task: calc usable space of PV before create PV and before create >> partition for >> PV. >> >> In my experiments usable space in PV = PVSize / ExtentSize * >> ExtentSize with >> integer operations. >> But when Metadata may be large - when LVM have a lot of logical >> volumes and it >> can take more space. >> >> I found in /etc/lvm/lvm.conf parameter pvmetadatasize = 255 secotors >> (default). >> What will if metadata will grow to more then 255 sectors? >> > > > If you plan to host lots of LVs within a single VG (in range of hundreds) > use i.e. 'pvcreate --metadatasize 5M' > (i.e. ~7000 linear single segment LVs takes around 2.2MB and you need > space for at least 2 metadatas to fit in) > > What I'm not quite sure is your 'task' - what's the purpose ? > Do you want to do some 'sector' precise emulation of what lvm2 is > doing by watching resuls of couple command with just subset of it's > options ? > > Isn't better to read man pages ? > > Zdenek > > _______________________________________________ > linux-lvm mailing list > linux-lvm@redhat.com > https://www.redhat.com/mailman/listinfo/linux-lvm > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ -- Timofey Koolin