Eddie's Blog

Understand Three Important Files in vSphere HA

This post is the note I take as I am reading the vSphere 6.x HA Deepdive book, plus my understanding of the materials.

Here we focuse on the files stored on the shared datastore, aka. remote files. Each host also restores some configuration files in a directly accessible datastore, aka. local files)

Protectedlist file
- Naming: protectedlist
- Owner: The master locks this protectedlist file
- The master uses this file to claim the “ownership” of the datastores stored the VM configuration file. When a host is isolated, if the host can access the datastore, then it will validate whether a master owns the datastores. If no master owns the datastores, the isolation response will not be triggered and restarts will not be initiated. (see page 29 & 30 of the book about isolation response).
- The master uses this protectedlist file to track the VMs protected by HA and the states of the VMs (powered on / off)
- The master distributes this protectedlist file to all datastores in use by the VMs in the cluster
"poweron" file
- Naming: host-<number>-poweron
- Owner: per-host (master & slaves)
- The host uses this "poweron" file to track the powered on virtual machines on a host
- The slaves use this "poweron" file to inform the master that it is isolated from the management network
  - No datastore heartbeat: the master determines a host has failed
  - The top line of "poweron" file is 1 (means isolated); if 0 means not-isolated
Heartbeat file
- Naming: host-<number>-hb
- Owner: per-host
- Each host creates a heartbeat file on the designed heartbeating datastores
  - On VMFS datastore, "heartbeat region" is used to check the heartbeat update
  - On NFS database, the time-stamp of the file is check (each host writes to its heartbeat file once every 5 seconds)

Disable Mac Startup Sound

A way to disable the Mac startup sound is to mute the speaker before shutting down the computer. But you have to remember to do that every time you unmute the speaker.

When I search on the web, some third party utilities are mentioned, e.g. StartupSound.prefPane or Psst or StartNinja or use sudo nvram SystemAudioVolume=%80. All these utilities are for the older version of Mac; and the nvram command doesn’t work my OS X El Capitan (version 10.11.3).

Finally, I find a way to mute the speaker automatically when log off. See this post for the full detail. I only set up the mute.sh, and don’t even bother the unmute.sh.

create a mute.sh script with the following lines

#!/bin/bash
osascript -e ‘set volume with output muted’

sudo chmod u+x ~/Documents/mute.sh
sudo mv ~/Document/mute.sh /Library/Scripts/
sudo defaults write com.apple.loginwindow LogoutHook /Library/Scripts/mute.sh

To restore the startup sound

sudo defaults delete com.apple.loginwindow LogoutHook

VMware vFlash Read Cache (VFRC) Notes

Available in vSphere 5.5 and 6.0 for basic caching solution

VMware introduces vSphere APIs for IO Filtering (VAIO) in vSphere 6.0 U1 as a new API framework for third party’s innovation
VAIO is not a feature or product.
It seems that VMware has no plan to create new caching product based on VAIO
VAIO can be used not only caching but also for replication

Some third party product can provide more advanced caching solution (both read and write-back cache, e.g. PernixData FVP)
Require Enterprise Plus License
Use local SSDs (must be on the HCL) to form a new file system called VFFS (Virtual Flash File System) to provide two types of write through (read only) caching

Per-VMDK cache
Host Swap cache

VFRC limitation (KB2057206)

Default VRFC maximum size is 200GB. Can be set to 400GB

Configuration

Set up VFRC resouce on a host

vSphere Web Client, host, Manage, Settings, Virtual Flash Read Cache Resource Management, Add capacity

Allocate VFRC to a VM’s VMDK

vSphere Web Client, VM, Edit Settings, select and expand the hard disk,and enter the amount of VFRC
The block size can impact performance, but it’s not easy to determine (see this post for detail)

Set up Host Swap Cache

vSphere Web Client, host, Manage, Settings, under Virtual Flash, edit Virtual Flash Host Swap Cache Configuration, Enable virtual flash host swap cache and enter the amount

Use Dig to Troubleshoot DNS Issue on Windows

Get dig.exe on Windows

Download and extract the BIND binary zip file to a folder from ISC.
Open a command prompt and navigate to the folder
Enter dig, no installation is required.

Basic syntax

dig @dns-server name type
dig @dns-server -q name -t type

Simplify the output

dig +nocmd +noall +answer @dns-server name
dig +nocmd +noall +answer +multiline @dns-server name any

Windows Page File Purposes and Sizing

Consider the following for page file sizing

System crash dump: the page file must exist and be larger than the physical memory (RAM)
Peak system committed memory:
- system committed memory = physical memory + all page files combined size
- The system with 8GB RAM + 1.3GB page file = 9.2GB committed RAM
Infrequently accessed pages: Infrequently accessed modified pages are removed from physical memory and stored in the page files. The “\Memory\Modified Page List Bytes” performance counter measures, in part, the number of infrequently accessed modified pages that are destined for the hard disk.

Extend or add a page file if all the following performance counters are true:

\Memory\Available MBytes is low (more available phyiscal memory is in use): less than 4 MB
\Memory\Modified Page List Bytes is high
\Paging Files(_Total)\%Usage is high: more than 70%

General recommendation

Windows Server DC and DFS replication, certificate, and LDS servers are not supported without a configured page file
Exchange Server requires a page file
Set a static page file size rather than dymantically managed by Windows
For Windows Server 2012 or R2 Hyper-V, the page file of the management OS (the host OS) should be left at the default of setting of “System Managed”
For 64-bit SQL Server, enable “Lock Page in Memory” for the SQL Server service account
For 64-bit SQL Server, set Page File to be a static 6 GB

Source:

How to determine the appropriate page file size for 64-bit versions of Windows
The Windows Page File and SQL Server (performance counter number)
Windows Page File Explained (example of page file size)

Use \\?\UNC\ on A UNC Name to Work Around Windows 260 Characters File Name Limit

Prefixing the file name with “\\?\” can work around the Windows 260 characters (up to 32,000 characters) file name limit in some command line utilities. For example, for local file, dir \\?\c:\longfilename.txt.

However, the syntax is different on a UNC name, it needs to be \\?\UNC\servername\share\longfilename.txt. For example, dir \\?\UNC\fileserver\dept\it\longfilename.txt.

Not all the command line utilities support this syntax.