From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 30 May 2014 15:36:59 +0100 From: "Richard W.M. Jones" Message-ID: <20140530143659.GP1302@redhat.com> References: <20140529204719.GD1302@redhat.com> <20140529210648.GA3955@redhat.com> <20140529211955.GE1302@redhat.com> <20140529215815.GA4183@redhat.com> <20140530090422.GB31293@redhat.com> <20140530133814.GB8830@redhat.com> <20140530134642.GL1302@redhat.com> <53888DA9.6090003@redhat.com> <20140530142602.GN1302@redhat.com> <20140530142926.GA9219@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20140530142926.GA9219@redhat.com> Subject: Re: [linux-lvm] Testing the new LVM cache feature 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: Mike Snitzer Cc: Heinz Mauelshagen , Zdenek Kabelac , thornber@redhat.com, LVM general discussion and development On Fri, May 30, 2014 at 10:29:26AM -0400, Mike Snitzer wrote: > sequential_threshold is only going to help the md5sum's IO get promoted > (assuming you're having it read a large file). Note the fio test runs on the virt.* files. I'm using md5sum in an attempt to pull those same files into the SSD. > > Is there a way to print the current settings? > > > > Could writethrough be enabled? (I'm supposed to be using writeback). > > How do I find out? > > dmsetup status vg_guests-libvirt--images Here's dmsetup status on various objects: $ sudo dmsetup table vg_guests-lv_cache_cdata: 0 419430400 linear 8:33 2099200 vg_guests-lv_cache_cmeta: 0 2097152 linear 8:33 2048 vg_guests-home: 0 209715200 linear 9:127 2048 vg_guests-libvirt--images: 0 1677721600 cache 253:1 253:0 253:2 128 0 default 0 vg_guests-libvirt--images_corig: 0 1677721600 linear 9:127 2055211008 $ sudo dmsetup status vg_guests-libvirt--images 0 1677721600 cache 8 10162/262144 128 39839/3276800 1087840 821795 116320 2057235 0 39835 0 1 writeback 2 migration_threshold 2048 mq 10 random_threshold 4 sequential_threshold 0 discard_promote_adjustment 1 read_promote_adjustment 0 write_promote_adjustment 0 $ sudo dmsetup status vg_guests-lv_cache_cdata 0 419430400 linear $ sudo dmsetup status vg_guests-lv_cache_cmeta 0 2097152 linear $ sudo dmsetup status vg_guests-libvirt--images_corig 0 1677721600 linear > But I'm really wondering if your IO is misaligned (like my earlier email > brought up). It _could_ be promoting 2 64K blocks from the origin for > every 64K IO. There's nothing obviously wrong ... ** For the SSD ** $ sudo fdisk -l /dev/sdc Disk /dev/sdc: 232.9 GiB, 250059350016 bytes, 488397168 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disklabel type: dos Disk identifier: 0x3e302f2a Device Boot Start End Blocks Id System /dev/sdc1 2048 488397167 244197560 8e Linux LVM The PV is placed directly on /dev/sdc1. ** For the HDD array ** $ sudo fdisk -l /dev/sd{a,b} Disk /dev/sda: 1.8 TiB, 2000398934016 bytes, 3907029168 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disklabel type: gpt Disk identifier: B9545B67-681D-4729-A8A0-C75CB2EFFCB1 Device Start End Size Type /dev/sda1 2048 3907029134 1.8T Linux filesystem Disk /dev/sdb: 1.8 TiB, 2000398934016 bytes, 3907029168 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disklabel type: gpt Disk identifier: EFA66BD1-E813-4826-88A2-F2BB3C2E093E Device Start End Size Type /dev/sdb1 2048 3907029134 1.8T Linux filesystem $ cat /proc/mdstat Personalities : [raid1] md127 : active raid1 sdb1[2] sda1[1] 1953382272 blocks super 1.2 [2/2] [UU] unused devices: The PV is placed on /dev/md127. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com Fedora Windows cross-compiler. Compile Windows programs, test, and build Windows installers. Over 100 libraries supported. http://fedoraproject.org/wiki/MinGW