PDA

View Full Version : Database performance slow on Windows DomU



stelgenkamp
08-Feb-2014, 23:29
Hello Everyone,

I could use your advise on the following :
I am running Xen on SLES 11 SP3

On this I have a Windows 7 Pro VM, running a Sybase database.
Database performance is, well, not fast.
I have the 2.1 VMDP installed.
Also I did all the LSO offloads on both the DomU and the DOM0

I also have a OES11 DomU working with my Raid where I have my volumes

Since the database is the companies main program, performance is important

Now I have been checking the throughput with Iperf.
Windows DomU => Dom0 87 Mbit/s
Dom0 => OES11 DomU 5.35 Gbit/s
Windows DomU => OES11 DomU 84.6 Mbit/s

On standard file copy from Windows DomU to OES11 DomU, I am getting 10.000 KB/s which is about the 80 Mbit/s
But when doing a backup from the Sybase database I am only getting 3000 KB/s only.

Can anyone confirm these throughput speeds are normal ?
Anyone ideas what could be causing the delay in database speed ?

Thanks, Stephan

ab
09-Feb-2014, 05:12
Is there some reason you are ruling out this as a Sybase issue? If the
problem only happens when using application X, and particularly when
application X may need to be doing a lot of other stuff at the time to
aggregate the data for the backup process, does that not seem to point at
application X? If you have this same setup but with Sybase in another
virtual environment (KVM, for example) or if you have another database
involved (MariaDB/MySQL, or PostgreSQL, for example), do those behave
differently or similarly? What kind of Sybase backup (including commands)
are you doing? Is Sybase needing to read all of the data at the same time
it is writing out, and is it doing so from the same disk or disk system
for both operations?

--
Good luck.

If you find this post helpful and are logged into the web interface,
show your appreciation and click on the star below...

stelgenkamp
09-Feb-2014, 11:10
Dear Ab,
Yes this maybe related to the application.
However this is the companies main program, and this uses the sybase database.
So changing the database is out of the question.

The VM only runs this program and database, it does nothing else.
I have assigned 4 cores to the VM, but it does not seem to matter in speed.
Also assigned 4 Gb of memory, to try and speed up everything.
The VM is running on a 80 Gb raw image file.

So what is your opinion on this setup ? any recommandations ?
Can you confirm these throughput speeds are normal for a Windows VM ?
Any other ideas what could be causing the delay in database speed ?

Stephan

KBOYLE
10-Feb-2014, 09:01
stelgenkamp wrote:

> Anyone ideas what could be causing the delay in database speed ?

Over the past several releases a variety of issues have surfaced
relating to TCP offloading in general and TSO offloading in particular.
If you search the knowledgebase for "ethtool" you can see some of them.
http://www.novell.com/support/


Try to disable all offloading in DomO and DomUs and see if throughput
improves. Try to enable them one at a time to see how throughput is
affected.

--
Kevin Boyle - Knowledge Partner
If you find this post helpful and are logged into the web interface,
show your appreciation and click on the star below...

stelgenkamp
10-Feb-2014, 10:39
Hai Kevin,
I did all the TSO and LSO offloads on both the DomU and the DOM0.
Any other recommandations ?
Can you confirm these throughput speeds are normal for a Windows VM ?
Any other ideas what could be causing the delay in database speed ?

Stephan

ab
10-Feb-2014, 13:01
On 02/09/2014 03:14 AM, stelgenkamp wrote:
>
> Dear Ab,
> Yes this maybe related to the application.
> However this is the companies main program, and this uses the sybase
> database.
> So changing the database is out of the question.

I'm not suggesting changing the database system, just verifying that this
is part of that program and not the overall environment. Until we know
more about what is happening knowing if it is normal or not is tricky.

> The VM only runs this program and database, it does nothing else.
> I have assigned 4 cores to the VM, but it does not seem to matter in
> speed.
> Also assigned 4 Gb of memory, to try and speed up everything.
> The VM is running on a 80 Gb raw image file.

Do you think this is a problem with processing power for some reason? Are
you seeing contention on the virtual processors during these operations?
My original response, about testing other databases and asking what else
the database was doing at the time, was not meant to be limited to
processing. Your initial complaint is about I/O, and usually I/O becomes
slowed significantly by other I/O (for example, if your database is
running normally and doing normal reads and writes at the same time you
are trying to have it create a backup) so I would probably focus more on
the disk system than processor and RAM unless you have evidence proving
the problem is due to a limitation of processor and/or RAM.

> So what is your opinion on this setup ? any recommandations ?

Same as before. Test other systems to verify this is (or is not) related
to the application. Post the actual commands being used that show the
slowness.

Other ideas: try swapping out the OS. windows isn't known for
high-performance (see the top 500 supercomputer list, for example) and
chances are that a DomU running Linux can perform better, assuming this is
at all related to the OS itself (I recall that Sybase is cross-platform...
correct me if wrong). I wouldn't try this first though, since the
evidence still seems to point at limitations on the application side.

> Any other ideas what could be causing the delay in database speed ?

Just what is mentioned above. Find the bottleneck based on evidence and
then test things that will help you verify or rule out hypotheses. This
is the reason for the suggestion about trying another DB for testing, or
stopping all other database activity when doing the backup, as well as
requesting the commands used. For example, if the commands used are
simply copying database file within the operating system (meaning the
database itself is not involved) then the database itself should not
matter and now you have an OS issue. On the other hand, if the commands
are within Sybase and instruct the system to, while doing production work
as well, create a backup of the database then you are now adding work o an
application that may already be I/O constrained, or to a system that may
already be I/O constrained due to the application doing reads/writes to
the same database (and system) that is now going to be used for creating
the backup.

--
Good luck.

If you find this post helpful and are logged into the web interface,
show your appreciation and click on the star below...

KBOYLE
10-Feb-2014, 17:11
stelgenkamp wrote:

> I did all the TSO and LSO offloads on both the DomU and the DOM0.

I'm not sure what that means...

I'm suggesting you disable all offloads to see if it helps your
performance. If ethtool shows it enabled, disable it.


> Can you confirm these throughput speeds are normal for a Windows VM ?

No I can't but they seem low.


--
Kevin Boyle - Knowledge Partner
If you find this post helpful and are logged into the web interface,
show your appreciation and click on the star below...