Comments on: Qemu 0.14.1 released! https://virtuallyfun.com/2011/05/13/qemu-0-14-1-released/ Fun with Virtualization Sat, 07 Apr 2012 15:06:31 +0000 hourly 1 https://wordpress.org/?v=7.0.1 By: TooMeeK https://virtuallyfun.com/2011/05/13/qemu-0-14-1-released/comment-page-1/#comment-10879 Sat, 07 Apr 2012 15:06:31 +0000 https://virtuallyfun.com/?p=24#comment-10879 I’ve reached 2GB/s inside VM running on SSD drive with cache=”writeback” option since it’s just buffering..

]]> By: PlezzeR https://virtuallyfun.com/2011/05/13/qemu-0-14-1-released/comment-page-1/#comment-1156 Thu, 08 Sep 2011 13:17:36 +0000 https://virtuallyfun.com/?p=24#comment-1156 In reply to PlezzeR.

Previous testing was on Windows 7 64-bit with Service Pack 1.
I spent testing on Windows XP SP3 32-bit. The results were different from the results on Windows 7.
Results Qemu 0.14.1 and 0.15.0 turned out the same.
Columns – parameters of cache.
Rows – virtual hard disk formats.
Host OS – Windows XP SP3 32-bit
Qemu 0.14.1 & 0.15.0 =>
|———|writethrough|writeback|unsafe|none|
————————————————
| raw | fast | fast | fast | fast|
| qcow | fast | slow | fast | slow|
| qcow2 | medium* | fast | fast | fast|
| vdi | fast | fast | fast | fast|
————————————————
* – There was a significant slowdown, but still the speed was high enough (about 3 – 5 seconds).
Since “writethrough” option is the default, it becomes clear why the write speed to a virtual hard drive was high on Windows XP. (maybe it becomes clear)

]]> By: neozeed https://virtuallyfun.com/2011/05/13/qemu-0-14-1-released/comment-page-1/#comment-1153 Wed, 07 Sep 2011 23:28:37 +0000 https://virtuallyfun.com/?p=24#comment-1153 In reply to PlezzeR.

Wow that is some fantastic information!!! I’ll have to crib that and write it up! but that is amazing I never even though to dig that far!!!!!

]]> By: PlezzeR https://virtuallyfun.com/2011/05/13/qemu-0-14-1-released/comment-page-1/#comment-1148 Wed, 07 Sep 2011 13:09:20 +0000 https://virtuallyfun.com/?p=24#comment-1148 Yes! 🙂 Problem solved! The problem was related to the write caching on the hard drive. Caching in Qemu depends on the parameter “-cache cacheparameter” in “-drive”. This option is described in detail in the documentation. cacheparameter is “none”, “writeback”, “unsafe”, or “writethrough”. “directsync” is in the documentation, but I have not worked. With and without caching – different speed of the disc.
I tested the write speed to virtual hard disk.
Checked the speed install MS-DOS 6.22 in Qemu 0.14.1 and 0.15.0.
fast – copying files takes 1 – 2 seconds with a single floppy.
slow – copying files takes longer than 20 seconds (maybe even more than one minute) with a single floppy.
Columns – parameters of cache.
Rows – virtual hard disk formats.
Host OS – Windows 7 64-bit
Qemu 0.14.1 =>
|———|writethrough|writeback|unsafe|none|
————————————————-
| raw | slow | fast | fast |slow |
| qcow | slow | slow* | fast | slow|
| qcow2 | slow | fast | fast | slow|
| vdi | slow | fast | fast | slow|
————————————————-
Qemu 0.15.0 =>
|———|writethrough|writeback|unsafe|none|
————————————————-
| raw | slow | fast | fast |fast |
| qcow | slow | slow* | fast | slow|
| qcow2 | slow | fast | fast | fast|
| vdi | slow | fast | fast | fast|
————————————————-
* – Why slow? I don’t know. 🙁
Interesting test results.
“writethrough” option is the default. The result was a low speed of write to the virtual hard disk.
I replaced “-hda disk1.qcow2” to
“-drive file=disk1.qcow2,if=ide,index=0,media=disk,cache=writeback”
And it works fast.

]]> By: neozeed https://virtuallyfun.com/2011/05/13/qemu-0-14-1-released/comment-page-1/#comment-1134 Tue, 06 Sep 2011 15:48:20 +0000 https://virtuallyfun.com/?p=24#comment-1134 In reply to PlezzeR.

I have no idea… here is a small test I just ran with Qemu 0.15.0 …

# time dd if=/dev/zero of=bla bs=1000000 count=50
50+0 records in
50+0 records out
50000000 bytes transferred in 48.727 secs (1026116 bytes/sec)
0m48.76s real 0m0.00s user 0m9.64s system

]]> By: PlezzeR https://virtuallyfun.com/2011/05/13/qemu-0-14-1-released/comment-page-1/#comment-1133 Tue, 06 Sep 2011 15:35:25 +0000 https://virtuallyfun.com/?p=24#comment-1133 In reply to neozeed.

On raw format writing speed – few KiloBytes per seconds. 4-10 Kb/sec 🙁
On XP works fine. Why?

]]> By: PlezzeR https://virtuallyfun.com/2011/05/13/qemu-0-14-1-released/comment-page-1/#comment-1132 Tue, 06 Sep 2011 14:39:45 +0000 https://virtuallyfun.com/?p=24#comment-1132 In reply to neozeed.

memory 4 GB
I run Qemu with
qemu.exe -M pc -L pc-bios -m 16 -boot menu=on -hda disk1.disk -fda DOS1.IMG

]]> By: neozeed https://virtuallyfun.com/2011/05/13/qemu-0-14-1-released/comment-page-1/#comment-1127 Tue, 06 Sep 2011 14:00:16 +0000 https://virtuallyfun.com/?p=24#comment-1127 In reply to PlezzeR.

I’ve never benchmarked the speed of the disks… I know that expanding/growing a qcow/qcow2/vmdk/vpc image can be quite painful, however if RAW is slow as well… That’d be quite bad.

How much memory do you have?

]]> By: PlezzeR https://virtuallyfun.com/2011/05/13/qemu-0-14-1-released/comment-page-1/#comment-1126 Tue, 06 Sep 2011 13:42:39 +0000 https://virtuallyfun.com/?p=24#comment-1126 Qemu operates at low speed with a virtual hard disk. I tried to format raw, qcow, vdi. On Windows XP 32-bit everything is fine. But for Windows 7 64-bit is such a problem. MS-DOS 6.22 is installed in Qemu on Windows 7, a few minutes, but on XP for a few seconds. Tried Qemu 0.14.0, 0.14.1, 0.15.0. Why such a low speed? 🙁 In Safe Mode, Windows 7 is still a problem, too. How to solve this problem on Windows 7? Can you help? Thanks in advance.
Sorry for my English.

]]> By: neozeed https://virtuallyfun.com/2011/05/13/qemu-0-14-1-released/comment-page-1/#comment-485 Fri, 13 May 2011 17:34:38 +0000 https://virtuallyfun.com/?p=24#comment-485 It was a lot easier to setup than I had anticipated… Then again the last time I looked at doing this it was 2007… I’m sure things have gotten a lot better since then!

And thanks!

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