Well, as we move from theory to practise, our first batch of Windows 7 machines has been deployed and rolled out into the production environment, and so far so very, very good. Microsoft has done a very impressive job with its newest suite of client and server products, and our deployment is being managed end-to-end with no third-party products required.

I thought this would be an opportune time to document some of the problems I’ve encountered so far in the build of our Windows 7 Standard Operating Environment (SOE). Given that we are moving from a Windows XP/Novell Netware environment, there are a whole raft of changes happening as well as having to deal with problems which were lurking behind the scenes, and that’s what I’ll talk about today.

One of our critical line-of-business applications is an authoritative administration/HR system, with a locally-installed GUI application which talks back to a SQL database. The database is hosted on SQL Server 2005 SP3 x64 which sits on a Windows Server 2003 SP2 x64 system. We started noticing that on the Windows 7 machines, the local GUI took forever to talk back to the SQL database. There were no error messages (irritatingly) but performance was so slow as to be unusable.

Of course, the first assumption is that there’s an incompatibility with the application. It’s not an unreasonable assumption given that any IT pro looking at Windows 7 has been conditioned to expect appcompat problems, particularly with Line of Business (LOB) applications. But on further investigation, performing a simple ODBC connectivity test produced the same performance results – in other words, taking the LOB application out of the equation, the problem was still present.

Next step – three cheers for Wireshark. A packet trace on the Windows 7 machine displayed Kerberos traffic between the client, server and domain controller, with an error from the DC that it was unable to verify the ticket request – KRB5KDC_ERR_S_PRINCIPAL_UNKNOWN. The client and server then renegotiated using NTLM and the connection was made. This was why there were no error messages, but did it explain the slow-down?

The error was due to an incorrect Service Principal Name (SPN) for the SQL server. This can happen when SQL Server is installed and the account used to start the SQL services is either a local or domain user rather than the Local System account. Standard user accounts don’t have the access rights in AD to update SPN records, whereas the Local System account uses the computer account of the server, which does have sufficient rights. Why didn’t this problem emerge before? Even though our XP workstations are connected to both AD and eDirectory, the “functionality” of the Novell Client means that when they talk out across the network, the workstations don’t identify themselves using standard the AD domain\username syntax. As a result Kerberos authentication isn’t attempted.

To update and verify the SPN in AD I used two tools – QUERYSPN.VBS and SETSPN. I ran these from the DC, but you can run them from any domain-joined workstation with an account with sufficient rights to modify AD. To check what information AD returns when queries are made, type in:

cscript queryspn.vbs mssqlsvc*

This queries AD for all instances of SQL server. If the SQL services on the problematic server are being started with a local/domain user account, the query should return something like:

CN=Username,CN=Users,DC=domain.com

Class: user

User Logon: Username

MSSQLSvc/servername.domain.com:1433

If this is not returned (as it wasn’t in my case), use SETSPN to create the service name:

SETSPN –S MSSQLSvc/servername.domain.com:1433 username

Using –S instead of –A will check for duplicate entries before adding the SPN. Also, this assumes that the SQL server is using the default port of 1433. If not, use whichever port is appropriate. Run QUERYSPN.VBS again and the correct result should be returned. Allow AD replication to take place and then restart SQL services.

I then ran another packet trace with Wireshark and the Kerberos issue was resolved, but the speed problem was still present (depressingly). Then, when remotely connected from home I noticed that the Windows server which hosts the SQL server was quite sluggish compared to the other systems I was connected to. This triggered a memory of something which cropped up when Windows Vista first came onto the scene, whereby Server 2003-based systems were very slow to respond to networking requests from operating systems later than Windows XP, and this was also a problem in Server 2003 SP2.

Turned out to be a simple registry fix on the server:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\EnableTCPA=1

Change this to EnableTCPA=0, reboot the server and all the performance issues were resolved. Phew!

Subscribe to 4sysops newsletter!

So the moral of this particular tale is that if you’re planning a Windows 7 deployment, then depending on your environment there may be hidden problems which Windows 7 will uncover, but for which the operating system itself isn’t necessarily the cause. As our deployment progresses I’ll keep bringing you our discoveries.

Until next time...

+1
3 Comments
  1. Fred 12 years ago

    Do you edit the default user profile? I do that heavily on my XP machines "the old fashion way":
    1. make a bunch of changes to a users profile
    2. use the User profile tool to copy the profile over the default user profile
    3. new profiles inherit all my changes from that profile

    MS doesn't "like/support" this method any longer but I have never found a good step-by step process I'm really satisfied with. They talk about running reg-hacks when the user logs on but, what a nightmare to collect all those changes and apply them that way.

    Wondering what, if anything you do there.

    +1

  2. Author
    James Bannan 12 years ago

    I certainly used to do that on the Windows XP machines, but now we're going solidly down the roaming profile path using the default user account (unmodified) as the profile of choice.

    Then we're using Group Policy Preferences in AD to customise the user experience, rather than relying on heavily customised default profiles. There's less management overhead and in a Windows 7/Server 2008 R2 environment they are reliably deployed and enforced. Of course, there's a fair bit of work and testing to set them up, but long-term it's definitely the way to go.

    +1

  3. Fred 12 years ago

    Hmm.. I'm a bit shy of roaming profiles. I have not visited them since I turn that feture off many years ago when migrating users from Windows NT to Windows 2000.

    Why?
    1. Last thing I want to do is copy a corrupt profile to another machine.
    2. "Junk" fills up a profile -references to old applications, temp files... it's like the user is a virus carrying around their bad habits to every machine they log on to.
    3. some users have 20GB of data on their desktop (I know that's awful but it happens).-then they go from Houston to Denver, log into a machine and want to know why it takes so long to log on.

    I think I could solve some of this with folder redirection.

    Anyway with fixed local profiles and some level of folder/registry backup I could be sure they didn't drag their trash around and have a copy of enough to save them if their machine died.

    To time rethink the whole shop....

    +1

Leave a reply

Please enclose code in pre tags

Your email address will not be published. Required fields are marked *

*

© 4sysops 2006 - 2021

CONTACT US

Please ask IT administration questions in the forums. Any other messages are welcome.

Sending

Log in with your credentials

or    

Forgot your details?

Create Account