[Xen-users] Re: Windows Disk performance

[Christian Tramnitz <chris.ace@xxxxxxx>]

Ruslan Sivak schrieb:
> I've been getting disappointing results on IO reads when using windows 
> guests.  I'm getting usually around 70MB/s reads using hdtune.  When 
> installing James' PV drivers, the speed drops to about 20MB/s.
> The host system is getting around 350MB/s reads.  I'm wondering if there 
> is such a significant slowdown, or if my tests are somehow flawed.  The 
> 70MB/s persisted throughout my VM testing, whether I was using Xen, 
> XenSource or VMWare Server.
> So my questions are:
>
> a.  Is there a bottleneck somewhere which basically caps the windows 
> disk performance?
> b. Is my testing methodology flawed.  Is there a better windows tool 
> that will measure performance?  What about Linux tool?  I'm currently 
> using hdparm -t
> Russ
Hi Russ,

first of all let's clarify:
- Is this Mb as in "Megabits per second" or MB as in "Megabytes per 
second"? You stated both in your original post in the 0.95 driver 
thread, so I want to make sure...
- Did you use the same measurement/tools in all 3 scenarios (dom0, 
domU/stock, domU/gplpv)? If yes how exactly? (I'm not aware of hdtune 
for linux, so you most probably ran something else to get dom0 performance)
I think the answer to #2 will explain the big difference between dom0 
and domU performance (taking into account a bit of a general overhead).
When it comes to PV driver's performance this is an interesting topic. 
I've seen posts giving the opposite (not exact numbers but direction) 
result, so it would be interesting to find out what causes this.


Best regards,
   Christian


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