Re: [Xen-devel] Re: poor domU VBD performance.

[Cédric Schieli <cedric@xxxxxxxxxxxxxxxxxx>]

I can confim the problem only occur on SATA.
I've added an old IDE UDMA66 drive, created LVM volume from it and ran
same dd tests :
Dom0 : 12 MB/s
DomU : 12 MB/s


> It just sumbled accross the fact, that you are using a SATA disk, Cédric. This
> is 
> exactly the "dd" behavior that  my system containing SATA disks still shows. 
> But 
> it
> applies only to "dd" ( which, admittedly is read-only ). It does not apply to 
> the performance figures I got when copying my "/usr" tree - as described in a 
> previous post here - from one location of the disk to another location on the
> same disk ( which, of course is combined read-write on the same device ). 
> Hence
> it might be possible that my limited performance copying from one disk to
> another might in fact be an effect of reduced read performance in DomU on a 
> SATA disk.  
> 
> I suspect that this might be an effect specific to SATA disks. I will verify 
> this on monday - when I have access to my computers in the office, by doing it
> on a system with two IDE disks. I will report it then, if your problem is 
> still
> open. 
> 
> I will describe the exact configuration of the systems then (Motherboard, IO 
> Controller, etc ).


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