From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx2.redhat.com (ext-mx01.rdu.redhat.com [10.11.45.6]) by int-mx12.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id q3OFJmSE029588 for ; Tue, 24 Apr 2012 11:19:48 -0400 Received: from smtp2-1.tng.de (smtp2-1.tng.de [213.178.66.95]) by mx2.redhat.com (8.13.8/8.13.8) with ESMTP id q3OFJkBf018676 for ; Tue, 24 Apr 2012 11:19:47 -0400 Received: from smtp2-2.tng.de (smtp2-2.tng.de [213.178.66.96]) by smtp2-1.tng.de (Postfix) with ESMTP id 60E9C7400E for ; Tue, 24 Apr 2012 17:19:44 +0200 (CEST) Received: from smtp.tng.de (proxy02.mailcluster.tng.de [82.97.146.16]) by smtp2-2.tng.de (Postfix) with ESMTP id 5954D9C0BB for ; Tue, 24 Apr 2012 17:19:44 +0200 (CEST) Received: from [213.178.67.139] (myrmidia.tng.de [213.178.67.139]) by smtp.tng.de (Postfix) with ESMTPSA id 50CD31FFE2 for ; Tue, 24 Apr 2012 17:19:44 +0200 (CEST) Message-ID: <4F96C48F.3040300@ki.tng.de> Date: Tue, 24 Apr 2012 17:19:43 +0200 From: Jan-Hendrik Palic MIME-Version: 1.0 References: <4F969B43.2080504@ki.tng.de> <20120424095252.15fdcb07@bettercgi.com> In-Reply-To: <20120424095252.15fdcb07@bettercgi.com> Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] calculating size of metadata. 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: linux-lvm@redhat.com Hi, On 24.04.2012 16:52, Ray Morris wrote: > It's good think about this because running out of metadata space is no > fun. We had this problem already on an other system. We had to migrate to another storage with pain. The new storage has a larger space for the metadata for sure. .-) But I want to understand and not only set this size to an high value. Therefore this question here. > We use 181KB for about 300 LVs, where each snapshot is counted as > two LVs because of the way it's stored. That's based on the size of the > backup. vgs shows 8 MB of metadata used, though: > > # vgs --units k -o vg_mda_count,vg_mda_free,vg_mda_size clones > vgs #VMda VMdaFree VMdaSize > vgs 3 7973.50k 16444.00k Thank you and Lars for your replies. If I understand you right, I have to look to the count of LVs I will have in the future and not only on the size of my volumegroup. Ok. > In any event, on a 19,950,000 MB partition, even 64 MB of metadata > would represent 0.0006% of the storage. To think of it another way, 64 > MB costs roughly 0.03 cents, so allocate plenty. Lars stated in his mail to this list, that one entry for a LV should be less than 1kb. So if I calculate 2kb for this entry, I will be safe. I checked this here and I can confirm this. If I have a metadata space of 64MB, I am able to create 32000 different LV (without snapshots). Right? Well, that is enought, even with snapshots, Anyway ... thank you for my enlightment. .-) Best regards Jan