Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtp (Exim 4.84_2) (envelope-from ) id 1av44C-0005Ng-CW for pgsql-performance@arkaria.postgresql.org; Tue, 26 Apr 2016 14:34:20 +0000 Received: from localhost ([127.0.0.1] helo=postgresql.org) by malur.postgresql.org with smtp (Exim 4.84_2) (envelope-from ) id 1av44B-0008AS-Uy for pgsql-performance@arkaria.postgresql.org; Tue, 26 Apr 2016 14:34:19 +0000 Received: from makus.postgresql.org ([2001:4800:1501:1::229]) by malur.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA384:256) (Exim 4.84_2) (envelope-from ) id 1av42V-0006I5-9t for pgsql-performance@postgresql.org; Tue, 26 Apr 2016 14:32:35 +0000 Received: from mail-ig0-x22c.google.com ([2607:f8b0:4001:c05::22c]) by makus.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.84_2) (envelope-from ) id 1av42R-00066G-MO for pgsql-performance@postgresql.org; Tue, 26 Apr 2016 14:32:34 +0000 Received: by mail-ig0-x22c.google.com with SMTP id u10so43399785igr.1 for ; Tue, 26 Apr 2016 07:32:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=hX+/+AgakmgCXONTB6IWuMcKBtQ9cPB2upYhnhRuc9s=; b=wwg6EZh5tzJjqiBXp+fiYpRi5ljujsRAO/Vixxca7gAU44iTjn1+MoEljq/TZpREAa vbl+iPge4imXdbDn0/UZfjIX0ngTvJPiGs2STjViMqutFAwBRlwPco/xr8wVGkh7QNmS RXNd0aMxpmCQ8yxsCID+MXwnYUEG0nY8Is/KbnhmG2tg+8gl5Nf/n3RewNL1p04NpsNA H/Ca7swAwFfktqO4vBvgV1cmZ5NRCra1fMgWZ6ARJlK3m81ApgMq+TZlosQYigrUT6uP 5K0hBOtC/t+Nx5qcDPULCRPLPyx3NmQsvXkdZmiBshg2P6hLxmvo7MhrSq5WMppsLoPp FUqw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=hX+/+AgakmgCXONTB6IWuMcKBtQ9cPB2upYhnhRuc9s=; b=GlL7sZnGhkZXJRYyQG6dZKlx4WPoAtZyuVmTyeAa1vPpKWN9tJiTOt2BvRf/T4SckZ FXSA31n4onWdnYzSk5Z32LKPQEXSPXCp4ofB5T6rgf2iDHSJyePWvvf8E78y9/Aq08S6 g+ihtn1+0uD37UPsuWzfwOdDh2K93j1w/ih3uUw0MPQGP4FVGDhGIXShMV28F1Ldoay0 Es5QNqf3bsDRErW4jAv7jQkluDmZnUt242ygpCpDq9P15RL7HT2jc0XKAO5qIxWj0wnO mKCs/ezFbgpAh2Hu0gNwP4+pNRnJMB1THiRap0qh3mJI5nTTvVrZCygo3Kb3/Mhv7J96 Y21w== X-Gm-Message-State: AOPr4FUaLqakoP25EhBbazssEkTd8yFtr13aaKJlR6SCNn4H3MyVRru0h0s6KZnWa1T1Ce8zmXMFjrwQ0yMEBw== X-Received: by 10.50.154.162 with SMTP id vp2mr896552igb.15.1461681148145; Tue, 26 Apr 2016 07:32:28 -0700 (PDT) MIME-Version: 1.0 Received: by 10.64.41.129 with HTTP; Tue, 26 Apr 2016 07:32:07 -0700 (PDT) In-Reply-To: References: From: Imre Samu Date: Tue, 26 Apr 2016 16:32:07 +0200 Message-ID: Subject: Re: Poor disk (virtio) Performance Inside KVM virt-machine vs host machine To: Artem Tomyuk Cc: "pgsql-performance@postgresql.org" Content-Type: multipart/alternative; boundary=14dae93407f39c3ae2053164294f X-Pg-Spam-Score: -2.7 (--) List-Archive: List-Help: List-ID: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: X-Mailing-List: pgsql-performance Precedence: bulk Sender: pgsql-performance-owner@postgresql.org --14dae93407f39c3ae2053164294f Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable >I've noticed that there is a huge (more than ~3x slower) performance difference between KVM guest and host machine. I don't know that this is relevant or not , but there is an IBM research paper (Published in 2014) "IBM Research Report - An Updated Performance Comparison of Virtual Machines and Linux Containers" http://domino.research.ibm.com/library/cyberdig.nsf/papers/0929052195DD819C= 85257D2300681E7B/ -> " As we would expect, Docker introduces no overhead compared to Linux, but KVM delivers only half as many IOPS because each I/O operation must go through QEMU. While the VM=E2=80=99s absolute performance is still quite hi= gh, it uses more CPU cycles per I/O operation, leaving less CPU available for application work. Figure 7 shows that KVM increases read latency by 2-3x, a crucial metric for some real workloads." Imre 2016-04-26 16:03 GMT+02:00 Artem Tomyuk : > Hi All. > > I've noticed that there is a huge (more than ~3x slower) performance > difference between KVM guest and host machine. > Host machine: > dell r720xd > RAID10 with 12 SAS 15 k drives and RAID0 with 2*128 GB INTEL SSD drives > in Dell CacheCade mode. > > *On the KVM guest:* > > /usr/pgsql-9.4/bin/pg_test_fsync -f test.sync > > 5 seconds per test > > O_DIRECT supported on this platform for open_datasync and open_sync. > > > Compare file sync methods using one 8kB write: > > (in wal_sync_method preference order, except fdatasync > > is Linux's default) > > open_datasync 5190.279 ops/sec 193 > usecs/op > > fdatasync 4022.553 ops/sec 249 > usecs/op > > fsync 3069.069 ops/sec 326 > usecs/op > > fsync_writethrough n/a > > open_sync 4892.348 ops/sec 204 > usecs/op > > > Compare file sync methods using two 8kB writes: > > (in wal_sync_method preference order, except fdatasync > > is Linux's default) > > open_datasync 2406.577 ops/sec 416 > usecs/op > > fdatasync 4309.413 ops/sec 232 > usecs/op > > fsync 3518.844 ops/sec 284 > usecs/op > > fsync_writethrough n/a > > open_sync 1159.604 ops/sec 862 > usecs/op > > > Compare open_sync with different write sizes: > > (This is designed to compare the cost of writing 16kB > > in different write open_sync sizes.) > > 1 * 16kB open_sync write 3700.689 ops/sec 270 > usecs/op > > 2 * 8kB open_sync writes 2581.405 ops/sec 387 > usecs/op > > 4 * 4kB open_sync writes 1318.871 ops/sec 758 > usecs/op > > 8 * 2kB open_sync writes 698.640 ops/sec 1431 > usecs/op > > 16 * 1kB open_sync writes 262.506 ops/sec 3809 > usecs/op > > > Test if fsync on non-write file descriptor is honored: > > (If the times are similar, fsync() can sync data written > > on a different descriptor.) > > write, fsync, close 3071.141 ops/sec 326 > usecs/op > > write, close, fsync 3303.946 ops/sec 303 > usecs/op > > > Non-Sync'ed 8kB writes: > > write 251321.188 ops/sec 4 > usecs/op > > > *On the host machine:* > > /usr/pgsql-9.4/bin/pg_test_fsync -f test.sync > > 5 seconds per test > > O_DIRECT supported on this platform for open_datasync and open_sync. > > > Compare file sync methods using one 8kB write: > > (in wal_sync_method preference order, except fdatasync > > is Linux's default) > > open_datasync 11364.136 ops/sec 88 > usecs/op > > fdatasync 12352.160 ops/sec 81 > usecs/op > > fsync 9833.745 ops/sec 102 > usecs/op > > fsync_writethrough n/a > > open_sync 14938.531 ops/sec 67 > usecs/op > > > Compare file sync methods using two 8kB writes: > > (in wal_sync_method preference order, except fdatasync > > is Linux's default) > > open_datasync 7703.471 ops/sec 130 > usecs/op > > fdatasync 11494.492 ops/sec 87 > usecs/op > > fsync 9029.837 ops/sec 111 > usecs/op > > fsync_writethrough n/a > > open_sync 6504.138 ops/sec 154 > usecs/op > > > Compare open_sync with different write sizes: > > (This is designed to compare the cost of writing 16kB > > in different write open_sync sizes.) > > 1 * 16kB open_sync write 14113.912 ops/sec 71 > usecs/op > > 2 * 8kB open_sync writes 7843.234 ops/sec 127 > usecs/op > > 4 * 4kB open_sync writes 3995.702 ops/sec 250 > usecs/op > > 8 * 2kB open_sync writes 1788.979 ops/sec 559 > usecs/op > > 16 * 1kB open_sync writes 937.177 ops/sec 1067 > usecs/op > > > Test if fsync on non-write file descriptor is honored: > > (If the times are similar, fsync() can sync data written > > on a different descriptor.) > > write, fsync, close 10144.280 ops/sec 99 > usecs/op > > write, close, fsync 8378.558 ops/sec 119 > usecs/op > > > Non-Sync'ed 8kB writes: > > write 159176.122 ops/sec 6 > usecs/op > > > The file system "inside" and "outside" the same - ext4 on LVM. Disk > scheduler "inside" and "outside" set to "noop". Fstab options same to, > setted to rw,noatime,nodiratime,barrier=3D0. OS on host and guest the sam= e > CentOS release 6.5 (Final). > > Guest volume options: > > Disk bus: Virtio > > Cache mode: none > > IO mode: native > > > Any ideas? > > > > > > > > > > --14dae93407f39c3ae2053164294f Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
>I've noticed that there is a huge (more than ~3x s= lower) performance difference between KVM guest and host machine.=C2=A0
=

I don't know that this is relevant or not , but=C2=A0there is = an IBM research paper (Published in 2014)
"IBM Research Report - An= Updated Performance Comparison of Virtual Machines and Linux Containers&qu= ot;
http://domino.research.ibm.com/library= /cyberdig.nsf/papers/0929052195DD819C85257D2300681E7B/
-> =C2=A0&= quot; As we would expect, Docker introduces no overhead compared to Linux, = but KVM delivers only half as many IOPS because each I/O operation must go through QEMU. While the VM=E2=80=99s absolute performance is still quite high, it uses more CPU cycles per I/O operation, leaving less CPU available for application work. Figure 7 shows that KVM increases read latency by 2-3x, a crucial metric for some real workloads."=C2=A0
<= br>Imre




2016-04-26 16:03 GMT+02:00 Artem Tomyuk= <admin@leboutique.com>:
Hi All.=C2=A0

I've noticed that t= here is a huge (more than ~3x slower) performance difference between KVM gu= est and host machine.=C2=A0
Host machine:=C2=A0
dell r7= 20xd=C2=A0
RAID10 with 12 SAS 15 k drives and RAID0 =C2=A0with 2*= 128 GB INTEL SSD drives in Dell CacheCade mode.

On the KVM guest:

=C2=A0/usr/pgsql-9.4/bin/pg_test_fsync -f test.sync

5 seconds per test

O_DIRECT supported on this platform for open_datasync and open_syn= c.


Compare file sync methods using one 8kB write:

(in wal_sync_method preference order, except fdatasync

is Linux's default)

=C2=A0 =C2=A0 =C2=A0 =C2=A0 open_datasync=C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 5190.279 ops/sec =C2= =A0 =C2=A0 193 usecs/op

=C2=A0 =C2=A0 =C2=A0 =C2=A0 fdatasync=C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 4022.553 ops= /sec =C2=A0 =C2=A0 249 usecs/op

=C2=A0 =C2=A0 =C2=A0 =C2=A0 fsync=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 3= 069.069 ops/sec =C2=A0 =C2=A0 326 usecs/op

=C2=A0 =C2=A0 =C2=A0 =C2=A0 fsync_writethrough=C2=A0 =C2=A0 =C2=A0= =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 n/a

=C2=A0 =C2=A0 =C2=A0 =C2=A0 open_sync=C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 4892.348 ops= /sec =C2=A0 =C2=A0 204 usecs/op


Compare file sync methods using two 8kB writes:

(in wal_sync_method preference order, except fdatasync

is Linux's default)

=C2=A0 =C2=A0 =C2=A0 =C2=A0 open_datasync=C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 2406.577 ops/sec =C2= =A0 =C2=A0 416 usecs/op

=C2=A0 =C2=A0 =C2=A0 =C2=A0 fdatasync=C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 4309.413 ops= /sec =C2=A0 =C2=A0 232 usecs/op

=C2=A0 =C2=A0 =C2=A0 =C2=A0 fsync=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 3= 518.844 ops/sec =C2=A0 =C2=A0 284 usecs/op

=C2=A0 =C2=A0 =C2=A0 =C2=A0 fsync_writethrough=C2=A0 =C2=A0 =C2=A0= =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 n/a

=C2=A0 =C2=A0 =C2=A0 =C2=A0 open_sync=C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 1159.604 ops= /sec =C2=A0 =C2=A0 862 usecs/op


Compare open_sync with different write sizes:

(This is designed to compare the cost of writing 16kB

in different write open_sync sizes.)

=C2=A0=C2=A0 =C2=A0 =C2=A0 =C2=A0 1 * 16kB open_sync write=C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 3700.689 ops/sec =C2=A0 =C2=A0 270 usecs/op

=C2=A0=C2=A0 =C2=A0 =C2=A0 =C2=A0 2 *=C2=A0 8kB open_sync writes = =C2=A0 =C2=A0 =C2=A0 =C2=A0 2581.405 ops/sec =C2=A0 =C2=A0 387 usecs/op

=C2=A0=C2=A0 =C2=A0 =C2=A0 =C2=A0 4 *=C2=A0 4kB open_sync writes = =C2=A0 =C2=A0 =C2=A0 =C2=A0 1318.871 ops/sec =C2=A0 =C2=A0 758 usecs/op

=C2=A0=C2=A0 =C2=A0 =C2=A0 =C2=A0 8 *=C2=A0 2kB open_sync writes= =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 698.640 ops/sec=C2=A0 =C2=A0 1431 usecs/= op

=C2=A0 =C2=A0 =C2=A0 =C2=A0 16 *=C2=A0 1kB open_sync writes=C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 262.506 ops/sec=C2=A0 =C2=A0 3809 usecs/op


Test if fsync on non-write file descriptor is honored:

(If the times are similar, fsync() can sync data written

on a different descriptor.)

=C2=A0 =C2=A0 =C2=A0 =C2=A0 write, fsync, close=C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 3071.141 ops/sec =C2=A0 =C2=A0 326 u= secs/op

=C2=A0 =C2=A0 =C2=A0 =C2=A0 write, close, fsync=C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 3303.946 ops/sec =C2=A0 =C2=A0 303 u= secs/op


Non-Sync'ed 8kB writes:

=C2=A0 =C2=A0 =C2=A0 =C2=A0 write=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 251321.1= 88 ops/sec =C2=A0 =C2=A0 =C2=A0 4 usecs/op


On the host machine:

/usr/pgsql-9.4/bi= n/pg_test_fsync -f test.sync

5 seconds per test

O_DIRECT supported on this platform for open_datasync and open_s= ync.


Compare file sync methods u= sing one 8kB write:

(in wal_sync_method preference order= , except fdatasync

is Linux's default)

= =C2=A0 =C2=A0 =C2=A0 =C2=A0 open_datasync =C2=A0 =C2=A0 =C2=A0 =C2=A0= =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 11364.136 ops/sec=C2=A0 =C2=A0 = =C2=A0 88 usecs/op

=C2=A0 =C2=A0 =C2=A0 =C2=A0 fdatasync= =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 12352.160 ops/sec=C2=A0 =C2=A0 =C2=A0 81 usecs/op

<= span>=C2=A0 =C2=A0 =C2=A0 =C2=A0 fsync=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 9833.= 745 ops/sec =C2=A0 =C2=A0 102 usecs/op

=C2=A0 =C2=A0 =C2= =A0 =C2=A0 fsync_writethrough=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 n/a

<= p>=C2=A0 =C2=A0 =C2=A0 =C2=A0 open_sync =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 14938.531 ops/sec= =C2=A0 =C2=A0 =C2=A0 67 usecs/op


Compare file sync methods using two 8kB writes:

(in wal= _sync_method preference order, except fdatasync

is Linux= 's default)

=C2=A0 =C2=A0 =C2=A0 =C2=A0 open_datasyn= c=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 7703.471 ops/sec =C2=A0 =C2=A0 130 usecs/op

=C2=A0 = =C2=A0 =C2=A0 =C2=A0 fdatasync =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 11494.492 ops/sec=C2=A0 =C2=A0 = =C2=A0 87 usecs/op

=C2=A0 =C2=A0 =C2=A0 =C2=A0 fsync=C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 =C2=A0 9029.837 ops/sec =C2=A0 =C2=A0 111 usecs/op

=C2=A0 =C2=A0 =C2=A0 =C2=A0 fsync_writethrough=C2=A0 =C2=A0= =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 n/a

=C2=A0 =C2=A0 =C2=A0 =C2=A0 open_s= ync=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0 =C2=A0 6504.138 ops/sec =C2=A0 =C2=A0 154 usecs/op

=


Compare open_sync with different write siz= es:

(This is designed to compare the cost of writing 16k= B

in different write open_sync sizes.)

=C2=A0=C2=A0 =C2=A0 =C2=A0 =C2=A0 1 * 16kB open_sync write =C2=A0 =C2=A0 = =C2=A0 =C2=A0 14113.912 ops/sec=C2=A0 =C2=A0 =C2=A0 71 usecs/op

<= p>=C2=A0=C2=A0 =C2=A0 =C2=A0 =C2=A0 2 *=C2=A0 8kB open_sync writes = =C2=A0 =C2=A0 =C2=A0 =C2=A0 7843.234 ops/sec =C2=A0 =C2=A0 127 usecs/op

=C2=A0=C2=A0 =C2=A0 =C2=A0 =C2=A0 4 *=C2=A0 4kB open_sync w= rites =C2=A0 =C2=A0 =C2=A0 =C2=A0 3995.702 ops/sec =C2=A0 =C2=A0 250 usecs/= op

=C2=A0=C2=A0 =C2=A0 =C2=A0 =C2=A0 8 *=C2=A0 2kB open_= sync writes =C2=A0 =C2=A0 =C2=A0 =C2=A0 1788.979 ops/sec =C2=A0 =C2=A0 559 = usecs/op

=C2=A0 =C2=A0 =C2=A0 =C2=A0 16 *=C2=A0 1kB open= _sync writes=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 937.177 ops/sec=C2=A0 =C2=A0= 1067 usecs/op


Test if fsync on = non-write file descriptor is honored:

(If the times are = similar, fsync() can sync data written

on a different de= scriptor.)

=C2=A0 =C2=A0 =C2=A0 =C2=A0 write, fsync, clo= se =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 10144.280 ops/sec=C2=A0= =C2=A0 =C2=A0 99 usecs/op

=C2=A0 =C2=A0 =C2=A0 =C2=A0 w= rite, close, fsync=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 8= 378.558 ops/sec =C2=A0 =C2=A0 119 usecs/op


Non-Sync'ed 8kB writes:

=C2=A0 =C2=A0 =C2=A0 =C2=A0=C2=A0write=C2=A0 =C2=A0 =C2=A0 =C2= =A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 1= 59176.122 ops/sec =C2=A0 =C2=A0 =C2=A0 6 usecs/op


The file system "inside" and "outside"= ; the same - ext4 on LVM. Disk scheduler =C2=A0"inside" an= d "outside" set to "noop". Fstab options same to, sette= d to rw,noatime,nodiratime,barrier=3D0. OS on host and guest the same CentO= S release 6.5 (Final).

Guest volume options:

Disk bus: Virtio

Cache mode: none

IO mode: native=C2=A0


Any ideas?=C2=A0





=C2=A0




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