Overview
The most popular expression of each consultant is "it depends" - we love this sentence and we use many J
However, the fact that you can say "it depends" do a good consultant course not - if a consultant can not give you clear answers it is kind of useless. Even though we usually say "it depends", most of the time there are answers to be correct in most cases.
Some design decisions are generally preferred and some are considered exceptions. Never trust consultant who always recommend the same solution for different problems and environments - "one size fits all" solution usually means that the solution is not quite mature and optimized for different scenarios (that's why I love our FlexCast - it can be really adapted according to customer needs). the unit
Provisioning services can be described as a unique solution that can also image unload IOPS read from your storage (read cache sits between your VM and storage).
When to Use Persistent Store
In theory, this is the perfect solution - a multi, you only manage a single image, all the problems can be easily solved simply by rebooting. But if you have some showstoppers - For example one of your critical applications require persistent data and does not work in read-only mode
When do you want to do your persistent data
- applications that require a persistent storage - typically applications that automatically generate machine-specific ID somewhere in the configuration files - SCCM, antivirus ...
- historical data you want to keep for auditing and or troubleshooting - generally different log files
- improved overall performance - sometimes persistent data storage can improve your performance -for example page file redirection and files frequently updates (especially if they do not use the delta updates)
- special requirements - one example can be the licensing grace period or application streaming cache. Or applications penalty first run
- Security - there is a potential gap in security when resetting the state of your computer by default before it will download all the updates check all requirements - like to start a time of Windows Firewall you protection, may want to keep these persistent data
How to enable
When you select the "Cache of the HDD device target" new drive is automatically mapped to each machine provisioned. On this disc, you can find two important parts - he and the rest of the write cache file reader. Upon restart, just write the cache file (.vdiskcache) is reset to the default state, while the rest of the disc is persistent.
Example write cache player
as you can see, persistent drive is just a regular workout and requires no special handling -. pAS HSM redirection or interception (such as isolation of the application or Personal vDisk)
A disadvantage is that you can not use all the built-in rules to specify which data are persistent and are not not
So how can you redirect the files folders and to persist?
How to use 1 - configuration change
The first is quite simple and depends on what you want to redirect - just change the location during installation or change in configuration. For example follow these simple steps to redirect your event log files. Same principle applies to most applications - if you can change the location, use
But if your application is hardcoded and you do not have an option to redirect.? Another option is to use the tools that are provided by the underlying operating system and the specific file system
How to use 2 -. Functionality of the base file system
Since Windows 00, Microsoft supports so-called junction points. NTFS junction NTFS is a feature that allows you to redirect seamlessly one folder to another. Technically, the junction points are just implementing the points of analysis - which contains special instructions (user data) are automatically processed by the file system driver (so Reparse point data users tag to identify stores + which driver should treat). Long story short, it is treated at a low level and your application does not require a specific point analysis support for profit.
System32 redirected to temporary directory (example)
junction points are extremely powerful when used correctly - I have used them many times to solve a problem with the application that used the roads hard - for example, if I wanted to install my application to D: ABC and ABC app used hardcoded C: ABC, I just installed in my folder and created the junction C: ABC <==> D :. ABC
Since Windows Vista 08, complete symlinks were introduced. While the junction points can connect to directories on a local volume, symbolic links are more powerful and actually supports all 4 R (emote) and L (ocal) scenarios - L2L, L2R, R2R and R2L ( so you can map your network shares your local folder).
Another great advantage of symlinks is that you can use to redirect files (not just files).
pagefile.sys redirected to the temporary directory (example)
So, if you need only redirect a single file you do not need to redirect the folder (usually configuration files that are related to the specific machine) together.
registry settings are more complicated of course - in general, I recommend the simple implementation, startup shutdown scripts
In very rare cases, you can not use (why not logon scripts Read my previous blog post?). . them - in this case solution is a bit more complicated and I do not want to enter into technical discussions (as it would be article on its own), but in general you should do the following:
1) Mont hive when starting
2.) implement your registry settings in this custom hive file
3.) implementing the type REG_LINK register to redirect data
But be careful
When designing persistence exceptions, you should be very careful (and CCS consult whenever possible).
First, the persistent data is something that goes against the idea of single image management. persistent data adds some uniqueness to each provisioned machines and makes it more difficult to troubleshoot - and if not properly designed, can even reduce performance over time
Also, do not forget that there a penalty -. storage requirements, since you will need to store persistent data.
Zugec Martin
Senior Consultant
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