[Xen-users] XEN, SLES9, DELL 6800 and ORACLE experience

[Sergey Lukashevich <lukash33@xxxxxxx>]

We started to play XEN a few weeks go. Now I would like to share our experience.
Our DELL 6800 have four 3Ghz ht 64bit Potomac processors, 12Gb of RAM, dual 
network card and plenty of disk space.

Our goal was using this machine for several SUSE Linux Enterprise Server v.9
virtual machines with Oracle RDBMS. The dom0 machine was to carry a production 
Oracle10g database. We would like to configure the dom0 Linux for the 
production. Production was to use only 4Gb of memory, all the 4(8 virtual) 
processors and some 100Gb of disk space. The rest of resources we planned to 
split into a few additional virtual SLES9 development and test sites with 
Oracle too.

We used xen 2.0.7 from source tree and SLES9 SP2. First we successfully 
installed all we wanted onto a PC with only one CPU and 512Mb of memory just to 
polish all the installation sequence because the installation guides of XEN is 
far from straightforward and the related XEN documentation is not satisfactory 
at. We managed it all on a PC: SLES9, XEN2.0.7 and Oracle10gR1. Everything went 
OK: Oracle runs test databases on both dom0 and domU Linuxes. Nevertheless we 
had to have previously removed 2 of 3 network cards from the PC to make Linux 
configure networking properly in every booting kernel. We need only one 
interface but the two spare network cards confused XEN.

Then we went to the dell6800 and installed SLES9.sp2 on it. We were glad seing 
full 12Gb in the output of Linux 'free' command. (SLES8 with Linux kernel 2.4 
showed only 4Gb there) The following RPMs we had to install before XEN:
        bridge-utils, 
        python, 
        python-devel, 
        curl-devel, 
        openssl-devel
Also we installed Twisted-1.3.0. (though not succeded with the newer version 
2.0)

Next we configured, compiled and installed pristine 2.6.11 linux kernel just to 
make sure it works ok with our DELL and with SLES9. It was.

Then we have the 2.6.11 patched with the XEN patch and make ARCH=xen 
menuconfig. The menu shows no ways to choose SMP support and (worse) no ways to 
choose SCSI low-level drivers we need!! Seems that they simply disappeared!

It took time to discover many error messages those 'make' generated just before 
showing the configuration menu up. They where like these:

 HOSTCC  scripts/lxdialog/yesno.o
 HOSTLD  scripts/lxdialog/lxdialog
scripts/kconfig/mconf arch/xen/Kconfig
/boot/config-2.6.5-7.191-bigsmp:26: trying to assign nonexistent symbol EVLOG
/boot/config-2.6.5-7.191-bigsmp:27: trying to assign nonexistent symbol 
EVLOG_FWPRINTK
/boot/config-2.6.5-7.191-bigsmp:35: trying to assign nonexistent symbol CKRM

and so on.

Fortunately different (but why so?) result where archived on the PC where we 
managed to compile the kernel for del6800 and its modules ok.

When at last the newlybuilt xen0 kernel was booted at del6800 it shows only one 
CPU in /proc/cpuinfo and only 1.5Gb of memory in the 'free' output. And the 
xen0 kernel was unable to do networking. Again XEN was confused by the "extra" 
network card. Networking was impossible because no default gateway was given to 
the interface. Though it could be fixed manually.

Later we have found from the XEN FAQ that XEN shows no "extra" processors but 
does use it running virtual machines one-by-one. 

As a result we decided to postpone our playing with XEN (for some months I 
think) until the project gets mature. The reasons are the following:
 1) The documentation lacks of proper installation instructions
 2) The documentation lacks of list of supported OSes and hardware 
configurations
 3) The documentation lacks of clear list of desired BUT STILL UNSUPPORTED 
features.
 4) The documentation lacks of clear list of desired BUT STILL UNSUPPORTED 
configurations.
 5) Limited support of SMP
 6) Limited support of large memory machines and x86/64
 7) Strange behaviour when more than one network card

Conclusion: Today XEN can not provide a platform for a few ORACLE servers. 
Mainly because they all must use more resources than a WEB server.

---
Sergey Lukashevich




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