From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mimecast-mx02.redhat.com (mimecast03.extmail.prod.ext.rdu2.redhat.com [10.11.55.19]) by smtp.corp.redhat.com (Postfix) with ESMTPS id F018FA37A5 for ; Tue, 1 Sep 2020 13:21:42 +0000 (UTC) Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [207.211.31.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 1342C811E7A for ; Tue, 1 Sep 2020 13:21:42 +0000 (UTC) MIME-Version: 1.0 Date: Tue, 01 Sep 2020 15:21:34 +0200 From: Gionatan Danti In-Reply-To: References: <83DAD1FF-6CE0-4725-A24D-2AE529433AEE@gmail.com> <8f19f639-107d-610d-0083-596d0c21a081@redhat.com> <29c466317b90d36bff995b3f3d0f4cf2@assyoma.it> Message-ID: <8a3a46b57b9264039885e8e7401e9dbd@assyoma.it> Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] lvm limitations 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: Zdenek Kabelac Cc: =?UTF-8?Q?Tomas_Dalebj=C3=B6rk?= , LVM general discussion and development Il 2020-08-30 21:30 Zdenek Kabelac ha scritto: > Hi > > Lvm2 has only ascii metadata (so basically what is stored in > /etc/lvm/archive is the same as in PV header metadata area - > just without spaces and some comments) > > And while this is great for manual recovery, it's not > very efficient in storing larger number of LVs - there basically > some sort of DB attemp would likely be needed. > > So far however there was no real worthy use case - so safety > for recovery scenarios wins ATM. Yes, I agree. > Thin - just like any other LV takes some 'space' - so if you want > to go with higher amount - you need to specify bigger metadata areas > to be able to store such large lvm2 metadata. > > There is probably not a big issue with lots of thin LVs in thin-pool as > long > as user doesn't need to have them active at the same time. Due to a > nature of > kernel metadata handling, the larger amount of active thin LVs from > the same thin-pool v1 may start to compete for the locking when > allocating thin pool chunks thus killing performance - so here is > rather better to stay in some 'tens' of actively provisioning thin > volumes when the 'performance' is factor. Interesting. > Worth to note there is fixed strict limit of the ~16GiB maximum > thin-pool kernel metadata size - which surely can be exhausted - > mapping holds info about bTree mappings and sharing chunks between > devices.... Yes, I know about this specific limitation. Thanks. -- Danti Gionatan Supporto Tecnico Assyoma S.r.l. - www.assyoma.it email: g.danti@assyoma.it - info@assyoma.it GPG public key ID: FF5F32A8