Re: [Xen-users] xen disk io performance

[George Shuklin <george.shuklin@xxxxxxxxx>]

"Very high" and "very slow" sounds like "i pay many buks but got small 
potion".
How many IOPS postgre generates from dom0 point of view? (see statistics 
in vbd/tap device in /sys). How do you did you check netapp storage 
performance?
FC is not synonym for 'fast work' and netapp ether can't do magic if 
postgre creates a thousands of cold random read operations.
I'll like to propose to starts from stat gathering. At least atop in 
domU with postgre with enabled logging.
On 28.11.2011 13:03, Alexandre Chapellon wrote:
> Hello,
>
> I have a setup with several xen 3.2.1 dom0s (debian). Most of the VMs 
> works nice but I have some load pick problem on some postgresql 
> instances. PGSQL has been tuned quite nicely I guess, but during some 
> jobs, IO load is very high and postgres seems really slow.
> I am using FC LUNs fomr a NetApp SAN (with fast FC 15000t/m disks) and 
> LVM as follow:
> FC LUNs are in a volume group (I had new LUNs on the VG when mre space 
> is needed) and VG is splited across several database servers (Xen 
> guests) using LVs.
> So my disk config for my VM look like this:
>
> disk =[ 'phy:/dev/xendata/postgresql-syslog:xvdb1:w']
>
> What can be done to improve disk IO and throuput?
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