From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [10.36.7.36] (vpn1-7-36.ams2.redhat.com [10.36.7.36]) by int-mx13.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id s9EDR6cI025765 for ; Tue, 14 Oct 2014 09:27:07 -0400 Message-ID: <543D24A9.9040907@redhat.com> Date: Tue, 14 Oct 2014 15:27:05 +0200 From: Zdenek Kabelac MIME-Version: 1.0 References: In-Reply-To: Content-Transfer-Encoding: 7bit Subject: Re: [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"; format="flowed" To: LVM general discussion and development Dne 13.10.2014 v 14:20 Kees de Jong napsal(a): > 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? > > https://github.com/jthornber/thin-provisioning-tools/blob/master/caching/cache_metadata_size.cc The recent lvm2 tools (git) should maintain the size of metadata device at proper size for any given cache pool data device size. Zdenek