Eddie's Blog

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.

Icacls - support
PowerShell (get-acl) - not support, because of .NET

For more info see

Long Paths in .NET, Part 1 of 3

Remove OneDrive from File Explorer Side Panel in Windows 10

On my work PC, I use OneDrive for Business instead of OneDrive. By default Windows 10 includes an OneDrive shortcut in File Explorer side panel.

Change the following registry key to remove it.

{HKEY_CLASSES_ROOT\CLSID\{018D5C66-4533-4307-9B53-224DE2ED1FE6}
In the subkey System.IsPinnedToNameSpaceTree change the DWORD from 1 to 0
No reboot required.

Source: Microsoft TechNet Forums

Use Sigcheck and VirusTotal to Scan Files for Malware

Sigcheck is a tool to check files digital signature, and recently is updated to auidt the root CA stores. And it can also be used to scan files for malware via VirusTotal.

Unless the -vs option is used, sigcheck only compares the hash of a file in VirusTotal’s database to determine whether the file contains malware.

Download the latest version of Sigcheck (as of 01/26/2016, v.2.42)
Unzip the zip file to a folder
Open Command Prompt as Administrator, and change to the folder
Run sigcheck.exe -vt, and enter y to agree the VirusTotal policy
To scan a file: sigcheck.exe -v <filename>
To upload a file that is not previously scanned to VirtualTotal; the file size is up to 128MB: sigcheck.exe -vs <filename>
To scan a folder and subfolder: sigcheck.exe -v -s <foldername>
To scan and create a CSV report: sigcheck.exe -v -s -c <foldername> > <report.csv>

Check the VT detection column for the number of antivirus engine deteted a malware and used
Open the URL in VT link in a browser to get the detail of the analysis - which antivirus engine and type of malware

Fix A VSAN Host Shows 0 of 0 Disks In Use

We have three hosts running on VSAN 6.1. Today the Disk Management in vSphere Client shows one of the hosts 0 of 0 Disk in Use.

And in VSAN General, it shows the warning of Mixed On-disk Format Version, and there is an upgrade button next to it. (Do Not Click It - I didn’t click it, and am not sure what the impact would be). Because our VSAN environment is built from scratch with VSAN 6.1, it is not upgrade from VSAN 5.5. It does not make sense the disk format requires an upgrade.