Skip to main content

Newbie datacenter lesson #2: Performance considerations

So you are finally doing it!  Moving everything to a colo site - so exciting! So much redundant input power!  So much reliable A/C!

So much latency between sites.

It made so much sense to move EVERYTHING over that the only consideration you gave any thought to was DFS/Folder Redirection (which does, indeed, stink over the WAN).  One other small fuzzy area you forgot about was AccPac (Sage ERP 200).

DFS/Folder Redirection - at least this was a known potential issue.  It's slow, but users can live with it if they must (and $ dictates wait they must).  But AccPac!  It's so un-useable at this point that immediate measures must be taken.

Latency, you ask - how awful is it?  27ms.  (both sites on 100mb fiber)

Yep, 27ms is enough to bring AccPac to its knees.  It turns out that AccPac is a rather old application, and has a neat feature called 'DBspy' that displays its age nicely.  If you watch the 'DBspy' monitor screen, simply clicking on a single widget-thing in AccPac yields dozens of SQL calls.  It's no wonder the entire app is slow now!  Going from <1ms to 27ms is a fairly significant multiplier.

Speaking with our AccPac rep, he informed us that what we are trying to do (workstations connecting to remote SQL) is not a good idea, and we have two alternatives:

  1. Move the server back.
  2. Set up terminal services/appServer at the colo, have the users connect via RDP/remoteApp instead.
I don't really want to mess with the finance folks' workflow, so local server it is.  Thankfully we only have 15-20GB of databases to move.  Does mean one more SQL Standard license to purchase, however.  Good thing we left that single Hyper-V box behind for domain controllers...

So the lesson is: Check with ALL of your vendors and review the planned changes with them, especially the legacy providers.


Popular posts from this blog

DFSR - eventid 4312 - replication just won't work

This warning isn't documented that well on the googles, so here's some google fodder:

You are trying to set up replication for a DFS folder (no existing replication)Source server is 2008R2, 'branch office' server is 2012R2 (I'm moving all our infra to 2012R2)You have no issues getting replication configuredYou see the DFSR folders get created on the other end, but nothing stagesFinally you get EventID 4312:
The DFS Replication service failed to get folder information when walking the file system on a journal wrap or loss recovery due to repeated sharing violations encountered on a folder. The service cannot replicate the folder and files in that folder until the sharing violation is resolved.  Additional Information:  Folder: F:\Users$\\Desktop\Random Folder Name\  Replicated Folder Root: F:\Users$  File ID: {00000000-0000-0000-0000-000000000000}-v0  Replicated Folder Name: Users  Replicated Folder ID: 33F0449D-5E67-4DA1-99AC-681B5BACC7E5  Replication Group…

Fixing duplicate SPNs (service principal name)

This is a pretty handy thing to know:

SPNs are used when a specific service/daemon uses Kerberos to authenticate against AD. They map a specific service, port, and object together with this convention: class/host:port/name

If you use a computer object to auth (such as local service):

If you use a user object to auth (such as a service account, or admin account):

Why do we care about duplicate SPNs? If you have two entries trying to auth using the same Kerberos ticket (I think that's right...), they will conflict, and cause errors and service failures.

To check for duplicate SPNs:
The command "setspn.exe -X

C:\Windows\system32>setspn -X
Processing entry 7
MSSQLSvc/ is registered on these accounts:
CN=SQL Admin,OU=service accounts,OU=resources,DC=company,DC=local

found 1 groups of duplicate SPNs. (truncated/sanitized)

Note that y…

Logstash to Nagios - alerting based on Windows Event ID

This took way longer than it should have to get here's a config and brain dump...

You want to have a central place to analyze Windows Event/IIS/local application logs, alert off specific events, alert off specific situations.  You don't have the budget for a boxed solution.  You want pretty graphs.  You don't particularly care about individual server states.  (see rationale below - although you certainly have all the tools here to care, I haven't provided that configuration)

ELK stack, OMD, NXlog agent, and Rsyslog.  The premise here is as follows:

Event generated on server into EventLogNXlog ships to Logstash inputLogstash filter adds fields and tags to specified eventsLogstash output sends to a passive Nagios service via the Nagios NSCA outputThe passive service on Nagios (Check_MK c/o OMD) does its thing w. alerting
Open Monitoring Distribution, but the real point here is Check_MK (IIRC Icinga uses this...).  It makes Nagios easy to use and main…