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.
Fix: DNS Event ID 4013
Summary: By default, AD integrated DNS is configured to wait for AD sync to complete, which could cause problems in situations where you're rebuilding your environment and don't have all AD Domain Controllers yet available.
Date: Around 2016
Refactor: 9 January 2025: Checked links and formatting.
Disable NTFS Access Time
Summary: How to disable contious updating of the NTFS Access Time.
Date: Around 2010
Refactor: 21 February 2025: Checked links and formatting.
The NTFS file system used in MS Windows operating systems is in fact some sort of database that keeps track of all the changes that happen on your hard disk. It uses a couple of file system attributes for that, the Created, Modified and Accessed timestamps. The first two are fairly common and are available by default in Windows explorer:
To see the accessed attribute click the “More…” option on the bottom of the list in the picture above:
Which results in an explrer view like this:
The NTFS driver automatically updates this timestamp every time a file is accessed, whether for reading or writing. The timestamp lists the date on which the file was last accessed and whether the file was opened and read or changed and saved.That means that every time you browse through a folder, view folder contents, Windows and the storage is busy updating the file timestamps.
In most cases the Accessed timestamp does not add much useful information so you might consider to turn this feature off. In the combined NetApp/VMware Storage best practices guide the recommendation is to turn this feature off unless it's a fileserver to prevent issues with your backup solution.
Df And Du Show Different Space Usage
Summary: What to do when df and du show different space usage.
Date: Around 2011
Refactor: 21 February 2025: Checked links and formatting.
Determining Number Of VMs Per VMFS Volume
Summary: How to determine how many VMs you can run on your vmware volumes.
Date: Around 2009
Refactor: 21 February 2025: Checked links and formatting.
This article explains the following article in more detail:
Yellow Bricks article: Max amount of VMs per VMFS volume
The reason for this is that both articles are quite technical and can be quite confusing. I have a lot of experience with storage and I would say a little bit more than the average system administrator but not like the guys who work with NetApp and EMC for 20 years. I thought I'd write an article on going through the articles step by step, excluding the steps that are not relevant for my environment, providing an extensive example to use for future references.
My environment:
- ESX 4.1 update 1
- VMs are for 80% Windows Server 2003 and 20% Windows Server 2008
- Storage is IBM NSeries N6060 which is a rebranded NetApp FAS3160
- Storage link is 4GB Fiber Channel
- Disks are Fiber Channel type
Excluded step: I'm not taking SCSI reservations into considerations. See the quote below on what kind of operations cause SCSI reservations. In my environment I do not expect these kind of operations to happen on a daily bases:
VMFS is a clustered file system and uses SCSI reservations as part of its distributed locking algorithms. Administrative operations, such as creating or deleting a virtual disk, extending a VMFS volume, or creating or deleting snapshots, result in metadata updates to the file system using locks, and thus result in SCSI reservations. Reservations are also generated when you expand a virtual disk for a virtual machine with a snapshot. A reservation causes the LUN to be available exclusively to a single ESX host for a brief period of time. Although it is acceptable practice to perform a limited number of administrative tasks during peak hours, it is preferable to postpone major maintenance or configuration tasks to off-peak hours in order to minimize the impact on virtual machine performance.
Remember that changing settings and or defaults could do more harm than good when you're not properly analyzing your environment. Default values are there for a reason.
To come to an actual number of Virtual Machines per VMFS volume we have to gather data first. Data gathering consists of two parts:
- Performance and settings data gathering
- Capacity data gathering