From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx1.redhat.com (ext-mx15.extmail.prod.ext.phx2.redhat.com [10.5.110.20]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id s9DCLQeK004782 for ; Mon, 13 Oct 2014 08:21:26 -0400 Received: from mail-ig0-f172.google.com (mail-ig0-f172.google.com [209.85.213.172]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s9DCLOxW028777 (version=TLSv1/SSLv3 cipher=RC4-SHA bits=128 verify=FAIL) for ; Mon, 13 Oct 2014 08:21:25 -0400 Received: by mail-ig0-f172.google.com with SMTP id r2so10111379igi.11 for ; Mon, 13 Oct 2014 05:21:24 -0700 (PDT) MIME-Version: 1.0 From: Kees de Jong Date: Mon, 13 Oct 2014 14:20:43 +0200 Message-ID: Subject: [linux-lvm] How to calculate the LVM SSD cache size? 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" Content-Transfer-Encoding: 7bit To: linux-lvm@redhat.com Hi, The documentation is not clear about how big the cache size should be for optimal performance. It only gives pointers about how big the meta data for the cache should be. "Create the cache metadata LV. This LV will hold cache pool metadata. The size of this LV should be 1000 times smaller than the cache data LV, with a minimum size of 8MiB." There is however an example in the man page with a 100GB OriginLV which apparently needs (at least) 10GB of cache size. But what is the math? I for example have 4 LV's I want to cache. 6GB, 60GB, 100GB and 2TB and I have a 240GB SSD which will act as the caching disk. Could someone please fill in the gaps here? Thanks! Kees.