From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [10.34.130.160] (dhcp130-160.brq.redhat.com [10.34.130.160]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t8ACxjTQ000956 for ; Thu, 10 Sep 2015 08:59:46 -0400 References: From: Zdenek Kabelac Message-ID: <55F17EC1.6070903@redhat.com> Date: Thu, 10 Sep 2015 14:59:45 +0200 MIME-Version: 1.0 In-Reply-To: Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] Strange dm-cache activity at startup 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 10.9.2015 v 11:30 Stefan Ring napsal(a): > I have a fairly simple dm-cache setup with one PV on an HDD partition > as the origin block device, and the cache LVs live on a partition on > an SSD. The cache is in writethrough mode. Since I have no prior > experience with this, I basically followed the lvmcache man page when > creating this setup a few months ago. > > Every morning at startup, the system immediately starts prolonged > activity on the devices involved in the cache setup. iostat shows > reading activity from the cache device and constant write activity on > the HDD. The HDD is fully utilized, and this goes on for more than an > hour. After that, everything goes into what I would consider the > "normal" state with only the IO activity going on that I actively > throw at it. > > Is this normal/expected? What does it do? Why does it write back huge > amounts of data to the HDD after each system start? > > Kernel is currently 3.17.8-200.fc20.x86_64 (Fedora) > Userland has been upgraded to fc22 meanwhile Please first try to use the latest kernel. Kernel 3.17 is almost a year old. Lots of optimizations went in meanwhile. It's pointless to hunt already fixed bug. Zdenek