Showing posts from September, 2011

BSOD (Blue Screen Of Death)

I have experienced few BSOD last week, after updating some of my device drivers on my workstation Windows 7 SP1 (x86). Since I was updating from Microsoft update, i was not suspecting that there might be problems with updated drivers. So, I have scheduled checkdisk of my HDD for surface scan, suspecting for bad sectors. Fortunately, my HDD was free of bad sectors, so I decided to examine the crash dump file using windbg. For more info how to obtain windbg, how to read small memory dump and how to setup symbols please check Microsoft articles : and .

Here is the output from my minidump :

0: kd> !analyze -v
*                                                                             *
*                        Bugcheck Analysis                                    *
*                                                               …

Asking yourself how many messages are transported in your Exchange organization ?

In my migration scenario for Exchange 2010 I was using Exchange calculator from Exchange team , and in order to calculate required number of IOPS per database (or server), one of the required input parameters are total messages per mailbox per day and average message size in KB. So, if you don't want just to guess number of total messages per mailbox per day and average message size, you can use Rob's script for gathering email statistics . From all the data gathered you can use "Received Total Messages" and "Sent Unique Total" to get Total Number of messages per user. Also, you can use Received MB Total and Sent Unique MB Total to count daily traffic in MB for each user. Using these two parameters you can count average number of total messages per mailbox per day, and average size in MB (KB) for…

You can't make your Exchange 2010 Jetstress tests to pass

If you're testing your disk subsystem for Exchange 2010 with Jetstress and you're unable to make it "green" pass because database read latency is higher than 20 msec than it's time for reducing number of threads and for fine tuning. But, if you reduce number of threads than you will lose number of IOPS.
For example: with 2 threads you can't achieve required number of IOPS and with 3 threads you're achieving number of IOPS but database read latencies are higher than 20 msecs, in that case you can use "SluggishSessions" parameter. You can find this parameter in JetstressConfig.xml file. By default this parameter is set to 1, you can start increasing this number by 1, which will make Jetstress to add pause between tasks. With increasing "SluggishSessions" parameter you will lose IOPS.

For example : with thread count 3 and SluggishSession 2, I was able to achieve required number of IOPS but database read latencies were still higher than 20…

Your VM running on Hyper V is not in sync (time)

I have experienced something strange on Hyper V cluster based on Windows Server 2008 R2 SP1 Enterprise and VM guest with same OS but Standard edition, with time synchronization enabled but VM was still out of sync.
I have checked that Windows time service was running and queried the source for synchronization and it was free running system clock !
After restarting the windows time service, the VM started to sync with local CMOS clock instead of synchronizing with host (parent partition).
I'm guessing that VM was not reading the setting for the time synchronization from the VM configuration, so I have disabled the setting and re enabled and restarted the windows time service, and finally within few seconds the VM was synchronizing the time with host :

One more thing : if the server is Windows 2008 R2 and the machine is not domain joined the windows time service will stop automatically. On reboot you can see the following event :

This behaviour is by default and you can find more in…