Mailinglist Archive: opensuse (1468 mails)

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Re: [opensuse] [OT] is there a virtual machine that IMPROVE performance by using harddisk as harddisk image
  • From: Matthias Bach <marix@xxxxxxxxx>
  • Date: Tue, 2 Jun 2009 17:59:36 +0200
  • Message-id: <200906021759.42943.marix@xxxxxxxxx>
Hi!

Am Dienstag 02 Juni 2009 17:57:46 schrieb Boyd Stephen Smith Jr.:
In <4A2547B0.8020706@xxxxxxxxx>, Sandy Drobic wrote:
Lars Marowsky-Bree wrote:
On 2009-06-02T22:07:17, Zhang Weiwu <zhangweiwu@xxxxxxxxxx> wrote:
As far as I know if the hard disk of the guest os is an image file on
the host OS, the host OS treats it as a file and offer to cache it in
the main memory. However if vmplayer access a partition or harddisk it
is not cached by the host OS's file system. That might make it even
slower. Unless of course the database is in particular on a raw device
that is directly accessed from the guest OS, as Sandy pointed out.

The caching doesn't make a difference, as it is not really different.

The question itself is not relevant. Fact is that performance will
increase a lot if you use a raw device.

Well, then that software is written poorly.

No, but in the latter case every access will involve two filesystems and an
emulated block device instead of only one filesystem. That additional overhead
is something you will always see in io bound applications.

Regards,
Matthias
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