Thursday, May 24, 2012

File is larger than the maximum size supported by datastore '

I got this error when trying to take a snapshot of a VM with a 1TB Thin Provisioned HDD:



Create virtual machine snapshot VM NAME


File <unspecified filename> is larger than the maximum size supported by datastore '<unspecified datastore>


The used space was only around 9GB.

The problem here is VMFS block size. When I formatted the VMFS LUN I did it using 4MB block size (seeing as how my largest VMDK file would be 1TB).

However (and I should have known this), the file size was just over 1TB (1,073,742,000.00KB). Had I created it with 900GB I probably would have been ok.

The solution? I moved the VM to a VMFS datastore that had 8MB block size (this allows for 2TB files).

Depending on who you talk to people will say that its a waste of space. I dont think it is. Yes, you do have several files attached to a VM that take only 20-30k (but because of the VMFS block size are actually taking 8MB for each file) but in the long run if you need a large VMDK file you need to do this. You lose more space when creating the LUN (my 1.5TB LUN is actually 1.36TB once I format) than you would by selecting a bigger block size.

For those of you not familiar with block size, you have a few options:


• 1MB block size – 256GB maximum file size
• 2MB block size – 512GB maximum file size
• 4MB block size – 1024GB maximum file size
• 8MB block size – 2048GB maximum file size

The block size determines the maximum size for any one file on the VMFS datastore. So, if you think you will need a VM with a hard drive size of 256GB you will need to have a 1MB block size, 512GB you will need 2MB, so on and so forth. Do not get this confused with the files that are INSIDE the VM (ie, windows OS files, etc). The block size is for the VMDK file and the files associated with the VM (config files, snapshot files, etc.)

Wednesday, May 16, 2012

The consistency check failed for the component Microsoft Exchange Server\Microsoft Information Store\

I was getting the above error when trying to backup our Exchange environment. I was using the Windows 2008 R2 backup utility.

It was working previously as I was backing up while migrating users from our 2003 Server. We moved several people one day and noticed that we only had around 6GB on our partition that held our log files. We started the backup utility and after several minutes we got this error. Even though the backup would continue we would get a message saying that we could not restore from this backup. We also noticed that the logs were not getting removed.

After much searching I found a post on the Microsoft Technet site that mentioned enabling circular logging, dismount and then remount the databases and then removing circular logging with another dismount and remount of the databases. This pretty much just deletes the logs for each database.

While this isn't the most ideal way (since now you can't replay your logs if anything happened between this step and a full backup), it worked and we were able to do a full backup.

We had to use the Windows backup utility until we got our third party backup software working properly.


User unable to login to RDP Farm after you re-enable them?

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