topic Re: Can virtual IP address cause performance problem. in Operating System - HP-UX

Can virtual IP address cause performance problem.

Can EKINGEN — Tue, 10 May 2005 13:11:34 GMT

Hi all,

on a N class hpux 11.0 server, we have a sybase server. it uses another A class as application server. To prepare servers for serviceguard I configured a virtual IP on host. database servers listens on vip and communicates with application server's vip.
Everything worked fine but after a while datase admin complained that sybase performance degraded. I had to de-condigure my vips, till we but new LAN cards for new IPs.
DNS entries are correct. nslookup works fine.
anybody experience this performance problem with virtual IPs? I have never had this problem with oracle databases.
I attach netstat -s and lanadmin -g of both servers :
on database servers.

Re: Can virtual IP address cause performance problem.

Steven E. Protter — Tue, 10 May 2005 13:23:42 GMT

I do not believe a properly configured virtual ip address can cause a peformance problem.

It should have the same network/netmask as the primary.

SEP

Re: Can virtual IP address cause performance problem.

Alex Lavrov. — Tue, 10 May 2005 13:28:09 GMT

I don't see any errors in your log.

When do you have the performance issue? Logging in or during the work?

*Check the network settings both on server and on the network stuff to ensure they are the same.
*Do a little test, login into your machine via vip and try to ftp some large file, check the performance.

Anyway, I have a heavy doubt that this can cause performance problems. You should monitor you system during the performance problems and see what are the memory/cpu and disk usage.

Btw, do you use nfs? In this case, if the network is not prperly configured (mostly 100HF/FD problems on the server and network switches), then it can cause problems.

Re: Can virtual IP address cause performance problem.

Can EKINGEN — Tue, 10 May 2005 13:29:11 GMT

Yes Steve, they have the same network parameters of course. But it is difficult to prove to database admin . Do you see any network problem with netstat or lanadmin outputs?

Re: Can virtual IP address cause performance problem.

Tony Scully_2 — Tue, 10 May 2005 14:49:45 GMT

Can you get the dbas to run a piece of sql locally on the server, then through the client connected via (1) the servers real IP (2) the virtual IP.
Not sure about sybase, but this can be doen easily on oracle using the tnsnames.ora on the client to change where it points.

I haven't seen any issues using virtual IPs myself, so I concur with the previous posters on that.

Cheers,

Tony.

Re: Can virtual IP address cause performance problem.

Steven E. Protter — Tue, 10 May 2005 14:59:55 GMT

Run glance and find out what the problem is.

Often the problem is the database. If its oracle, let him install the stats pack and the databse might assist in tuning itself.

He/She should collect some stats as well.

SEP

Re: Can virtual IP address cause performance problem.

Matthew Ghofrani — Wed, 11 May 2005 08:55:13 GMT

In your lan configs, it is very important that your settings match with what your network folks have set up in their end. For example the speed and auto nego off/on has a big impact on perf if they don't match. They would work but with a big hit on perf.

Matthew from Boston

Re: Can virtual IP address cause performance problem.

Rita C Workman — Wed, 11 May 2005 09:04:05 GMT

Let's see...your up and then 'after awhile' your DBA says performance is degrading.
And someone is blaming a floating IP.

......Nah.......As Clay might say..."that dog just don't hunt !"

Sounds more like memory (i.e. some screwy app not releasing resources properly) to me.

Around here they USED to say...."..it must be the network..or the server". Sounds like the same thing to me. Do a little research, and you'll probably find it's a leak...

Rgrds,
Rita

Re: Can virtual IP address cause performance problem.

rick jones — Wed, 11 May 2005 09:34:41 GMT

since virtual IP's (lan0:1 etc) are completely transparant to the data link layer (lanadmin) there is no way in knuths little green algorithm that adding a virtual IP would have any effect on duplex settings for a NIC. if the duplex settings were good before, they would remain good after and if they were bad before, things would have been bad before as well.

Re: Can virtual IP address cause performance problem.

Can EKINGEN — Wed, 11 May 2005 16:05:17 GMT

Thanks all for answering. Indeed before turning their eyes to Virtual IPs, everything was blamed, kernel,hardware, emc disks etc... Nothing was found. I don't see any resource problem on servers. They claimed they see dropped packages, and HBA cards switching between IPs can cause slowdown. (that's why I attached netstat outputs, if you catch something that I miss).
Only thing I can imagine is database is sybase and it uses an interface file. Maybe sybase is getting confused even though dns works fine. I will ask it to a sybase news group .

Re: Can virtual IP address cause performance problem.

rick jones — Wed, 11 May 2005 16:16:40 GMT

your netstat/lanadmin stats look ok. in particular, the lanadmin stats have nothing in them to indicate a duplex mismatch.

netstat -s statistics since boot are not always that useful - running two snapshots separated in short time by beforeafter (ftp.cup.hp.com/dist/networking/tools/) would be good, and you could do that with the VIP added and with the VIP taken away (make sure it is from times with similar load)