SHIFT-WIKI - Sjoerd Hooft's InFormation Technology
This WIKI is my personal documentation blog. Please enjoy it and feel free to reach out through blue sky if you have a question, remark, improvement or observation. See below for the latest additions, or use the search or tags to browse for content.
Lun Aligning
Summary: This post is about aligning disks in a virtual environment to prevent IO congestion.
Date: 10 November 2011
Refactor: 3 January 2025: Checked links and formatting. Removed some old content.
For information about why you should keep LUNs aligned with your vmdks I'd like to refer to this article from yellow-bricks.com. It explains why alignment is important, but to sum it up: it comes down to performance. When the LUNs, vmdk and Guest OS blocks are not aligned the array will request more blocks than the VMs are actually asking for, causing more IO then required.
Please note the following remarks:
- Windows Server 2008 and Windows Vista are aligned by default if the VM was created as Windows Server 2008/Windows Vista.
- LUNs less than 4GB in size will align to 64KB
- LUNs larger than 4GB will align to 1MB
- Citrix Servers are not supported because they remap the C-drive.
- Windows Dynamic Disks are not supported and will be corrupted if an alignment is performed, you will be warned with something like this: “partition type: unknown - 0x42”. Do not align these partitions.
- Linux LVM volumes are not supported.
- If you align linux guests that use grub as their boot loader you'll have to reinstall grub
- Windows Server 2003 non-boot disks that have been added (d:, e:, etc) will need to be remapped in Computer Management. The drive letter will be lost on alignment.
- Because the virtual disks are being recreated you'll need enough free space on your volume/datastore.
- Aligning can only be done on VMs that are turned off (so downtime)
- Aligning is not supported on VMs that have snapshots or linked clones
Log Cleanup
Summary: How to cleanup old logs using a very simple script.
Date: Around 2014
Refactor: 6 March 2025: Checked links and formatting.
# Set var to directory which needs to be cleaned up
LOGDIR=/var/log/app/logs
cd $LOGDIR
find . -type f -ctime +28 -name 'applogfile.log*' -exec rm {} \;
find . -type f -ctime +28 -name 'app2logfile.log*' -exec rm {} \;
Note: this cleanup script removes files more than 4 weeks ago and have a name that starts with applogfile.log or app2logfile.log.
Other options are -mtime, for files that were modified more than 4 weeks ago.
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A GPO to Make Everyone Local Administrator
Summary: How to make a GPO to make every domain user a local administrator.
Date: Around 2009
Refactor: 6 March 2025: Checked links and formatting.
This is how to make a GPO to make every domain user a local administrator. Please remember that this is not best practice and you should have a really good reason to do this.
Active Directory Diagnostic Event Logging
Summary: How to make event viewer show information that's actually useful?
Date: Around 2015
Refactor: 6 March 2025: Checked links and formatting.
How to make event viewer show information that's actually useful when trying to troubleshoot AD's LDAP?