Thanks Kir, the /dev/zero makes sense I suppose. I tried with /dev/random
but that blocks pretty quickly - /dev/urandom is better, but still seems to
be a bottleneck.
As for the dbench results, I'd love to hear what results others obtain from
the same test, and/or any other testing approaches that would give a more
"acceptable" answer.
Regards,
J J
On Fri, May 2, 2014 at 4:01 PM, Kir Kolyshkin <k...@openvz.org> wrote:
> On 05/02/2014 03:00 PM, jjs - mainphrame wrote:
>
> Just for kicks, here are the data from the tests. (these were run on a
> rather modest old machine)
>
>
>
> Here are the raw dbench data:
>
>
> #clients vzhost simfs CT ploop CT
> ---------------------------------------------------------------------
> 1 11.1297MB/sec 9.96657MB/sec 19.7214MB/sec
> 2 12.2936MB/sec 14.3138MB/sec 23.5628MB/sec
> 4 17.8909MB/sec 16.0859MB/sec 45.1936MB/sec
> 8 25.8332MB/sec 22.9195MB/sec 84.2607MB/sec
> 16 32.1436MB/sec 28.921MB/sec 155.207MB/sec
> 32 35.5809MB/sec 32.1429MB/sec 206.571MB/sec
> 64 34.3609MB/sec 29.9307MB/sec 221.119MB/sec
>
>
> Well, I can't explain this, but there's probably something wrong with the
> test.
>
>
>
> Here is the script used to invoke dbench:
>
> HOST=`uname -n`
> WD=/tmp
> FILE=/usr/share/dbench/client.txt
>
> for i in 1 2 4 8 16 32 64
> do
> dbench -D $WD -c $FILE $i &>dbench-${HOST}-${i}
> done
>
> Here are the dd commands and outputs:
>
> OPENVZ HOST
> ----------------
> [root@vzhost ~]# dd bs=1M count=512 if=/dev/zero of=test conv=fdatasync
> 512+0 records in
> 512+0 records out
> 536870912 bytes (537 MB) copied, 11.813 s, 45.4 MB/s
> [root@vzhost ~]# df -T
> Filesystem Type 1K-blocks Used Available Use% Mounted on
> /dev/sda2 ext4 20642428 2390620 17203232 13% /
> tmpfs tmpfs 952008 0 952008 0% /dev/shm
> /dev/sda1 ext2 482922 68436 389552 15% /boot
> /dev/sda4 ext4 51633780 3631524 45379332 8% /local
> [root@vzhost ~]#
>
>
> PLOOP CT
> ----------------
> root@vz101:~# dd bs=1M count=512 if=/dev/zero of=test conv=fdatasync
> 512+0 records in
> 512+0 records out
> 536870912 bytes (537 MB) copied, 2.50071 s, 215 MB/s
>
>
> This one I can explain :)
>
> This is caused by ploop optimization that was enabled in the kernel
> recently.
> If data block is all zeroes, it is not written to the disk (same thing as
> sparse files,
> just for ploop).
>
> So you need to test it with some real data (anything but not all zeroes).
> I am not sure how fast is /dev/urandom but this is one of the options.
>
>
> root@vz101:~# df -T
> Filesystem Type 1K-blocks Used Available Use% Mounted on
> /dev/ploop11054p1 ext4 4539600 1529316 2804928 36% /
> none devtmpfs 262144 4 262140 1% /dev
> none tmpfs 52432 52 52380 1% /run
> none tmpfs 5120 0 5120 0% /run/lock
> none tmpfs 262144 0 262144 0% /run/shm
> root@vz101:~#
>
>
> SIMFS CT
> ----------------
> root@vz102:~# dd bs=1M count=512 if=/dev/zero of=test conv=fdatasync
> 512+0 records in
> 512+0 records out
> 536870912 bytes (537 MB) copied, 12.6913 s, 42.3 MB/s
> root@vz102:~# df -T
> Filesystem Type 1K-blocks Used Available Use% Mounted on
> /dev/simfs simfs 4194304 1365500 2828804 33% /
> none devtmpfs 262144 4 262140 1% /dev
> none tmpfs 52432 52 52380 1% /run
> none tmpfs 5120 0 5120 0% /run/lock
> none tmpfs 262144 0 262144 0% /run/shm
> root@vz102:~#
>
> Regards,
>
> J J
>
>
>
>
> On Fri, May 2, 2014 at 2:10 PM, jjs - mainphrame <j...@mainphrame.com>wrote:
>
>> You know the saying, "when something seems too good to be true"...
>>
>> I just installed centos 6.5 and openvz on an older machine, and when I
>> built an ubuntu 12.04 CT I noticed that ploop is now the default layout.
>> Cool. So I built another ubuntu12.04 CT, identical in every way except that
>> I specified smifs, so I could do a quick performance comparison.
>>
>> First I did a quick timed dd run, then I ran dbench with varying
>> numbers of clients.
>>
>> The simfs CT showed performance roughly similar to the host, which was
>> not too surprising.
>> What did surprise me was that the ploop CT showed performance which was
>> significantly better than the host, in both the dd test and the dbench
>> tests.
>>
>> I know someone will tell me "dbench is a terrible benchmark" but it's
>> also a standard. Of course, if anyone knows a "better" benchmark, I'd love
>> to try it.
>>
>> Regards,
>>
>> J J
>>
>
>
>
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