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fernandobonfim-9257 asked fernandobonfim-9257 edited

ReadyBoost - What data is cached?

I am trying to understand the ReadyBoost feature that is still available in Windows 10. I get that it stores some data into a flash drive so they may be accessed faster, sent to the RAM, and then used by the CPU. However, I still don’t understand what data ReadyBoost stores on the flash device.

Searching through the web I came to three possible answers:

1 - ReadyBoost stores the data picked by SuperFetch;

Some sources suggest that ReadyBoost works alongside another Windows feature: SuperFetch. SuperFetch is explained as a kind of limited artificial intelligence created to identify patterns on the user activity, so it may predict what the user is going to do in a given time. Knowing this information, it may load data into the RAM before the user needs it.|1||2||3||4| Though, I think it also stores some data in the virtual memory when there is not enough RAM to accommodate all of it.

According to a text on HowToGeek, the ReadyBoost would work with SuperFetch by loading the data selected into a flash drive instead of occupying the RAM with them.|1| On TechRepublic a slightly different function is given to ReadyBoost: instead of storing into the flash-based external memory prefetched data that would go to the RAM, it redirects prefetched data that would go to the virtual memory into flash drive,|2| Michael Fortin, who led the Windows Client Performance Team at the time SuperFetch and ReadyBoot were developed, said basically that ReadyBoost is intended to manage “SuperFetched” data in a flash device.|3| An overview of the Windows features used to improve performance in Windows 7 says that ReadyBoost “provides a dedicated area where SuperFetch can securely store a copy of performance-crucial data.”|4|

Also, ReadyBoost creates a cache file named readyboost.sfcache into the flash-based device. The extension of this file (.sfcache) seems to refer to the SuperFetch feature.

Despite the slightly differences in the information, they all seems to suggest that ReadyBoost places the data that SuperFetch thinks the user is going to need next into the flash drive, In this case, every single data in the flash drive would be there because it has been chosen by the SuperFetch feature.

2 - ReadyBoost make a complete copy of the virtual memory (page file);

According to Matt Ayers, who is referred to as the owner of this feature in some texts posted at the time of Windows Vista, and a post in the old Windows Vista Team Blog, the ReadyBoost technology copies the virtual memory (page file) content to the flash drive.|5||6||7|

Based on some research I get that virtual memory is a technique that allows the use of a portion of the secondary memory like a primary memory. This memory is used to overcome RAM shortage by temporarily holding some data from the RAM into a HDD, or whatever is being used as the secondary memory. This allows the computer to prioritize physical memory to data that is more important at the moment.|8| Besides that, the virtual is also used to store all the content from the RAM in the situation of a system crash.|9| We may assume that it also holds the data picked by SuperFetch based on how Matt explains the relation between both technologies: he says that ReadyBoost interacts with SuperFetch because the program-usage data is saved in the page file when there is not enough RAM, thus, by saving a copy of the virtual memory in the flash drive, ReadyBoost is also copying the cache created by SuperFetch, but not only that.|7|

If that is the case, the ReadyBoost drive would hold data selected by SuperFetch, data that is less important to be in RAM, and crash dump when needed.

3 – ReadyBoost will cache any data.

Mark Russinovich says that ReadyBoost asks SuperFetch to prepopulate the cache file created in the flash drive. After that, the Ecache.sys would monitor the reads and writes to the hard disk and copy any data being written into the cache file. Maybe what is being read is also cached, but it is not stated clearly in the text.|10|

In this case, any data could be in the flash device, since anything that is getting stored into the secondary storage is copied to the flash-based drive.

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I could not find an official and updated and detailed documentation that could clarify this for me. So, what data is stored into a ReadyBoost drive? I would appreciate any help on this topic, but I really need to know a way to check the information.

Note: Unfortunately I could not find a more specific tag to this topic.


windows-10-general
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hello i lost my recovery key for bitlocker but ihave this code DA46905C-E333-48E5-8404-5F83CE9372FF i need recovery key please can help me

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Hi,

Just checking in to see if the information provided was helpful.

If the reply helped you, please remember to accept as answer.
If no, please reply and tell us the current situation in order to provide further help.

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Hello,
There is a page describing how to do analysis on readyboost, may take a bit of work to analyze it
https://docs.microsoft.com/en-us/previous-versions/windows/desktop/xperf/readyboot-analysis


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Hi, Dgorter.

That text is about ReadyBoot analyses, not ReadyBoost.

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DSPatrick avatar image
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DSPatrick answered ashrafnassef-6190 commented

Something here might help.
https://docs.microsoft.com/en-us/archive/blogs/tomarcher/readyboost-qa

--please don't forget to upvote and Accept as answer if the reply is helpful--



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Hi, thanks for the answer.

I have already read the Q&A in that link. It is the item |5| in the question I posted. This seems to infer that the page file is copied to the flash-based device. However, I have found different answers in other texts. For instance, in the Windows PC Accelerators paper (item |4| in the question) provided in the Microsoft website, it is said that ReadyBoost “provides a dedicated area where SuperFetch can securely store a copy of performance-crucial data.”.

I cannot say which of the two statements are correct, or even if both are right.

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hello i lost my recovery key for bitlocker but ihave this code DA46905C-E333-48E5-8404-5F83CE9372FF i need recovery key please

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This is a different thread you need to create a new thread with your problem.

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thank you

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JennyFeng-MSFT avatar image
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JennyFeng-MSFT answered fernandobonfim-9257 commented

Hi,
Based on my research, it is really hard to find official and updated and detailed documentation.
To be honest, for your demand, open a support ticket with Microsoft should be a more effective way than ask in Q&A.
https://support.microsoft.com/en-gb/hub/4343728/support-for-business

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hello i lost my recovery key for bitlocker but ihave this code DA46905C-E333-48E5-8404-5F83CE9372FF i need recovery key please

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Thanks for the answer, JennyFeng.

It seems that the service in the site you linked is for business. May an ordinary user still use it to get information?

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Hi.
you could start here:
https://support.microsoft.com/contactus

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Hi

Sorry for the delayed response!

Well, I contacted Microsoft technical support twice last month.

Based on my first contact I would conclude that ReadyBoost copies part of the page file, deciding what to cache in the .sfcache file on-the-fly.

But then I realized that everytime I disable Sysmain service, which is referred as a newer name for the SuperFetch service, the ReadyBoost feature stops working.|1| I was willing to see how much difference ReadyBoost would do without one of the features that helps Windows to perform faster.

I contacted Microsoft again, and the explanation is that ReadyBoost relies on SuperFetch to select the data to be loaded to the ReadyBoost device.

Also, I read again the sources I have found so far, and on the Windows PC Accelerators it is said that ReadyBoost, SuperFetch and ReadyDrive are included in the Sysmain service. This means that disabling Sysmain would disable ReadyBoost even if it does not depend on SuperFetch. |2|

So, I ended up stuck again with the 1st and 2nd possible answers.

Since I could be misunderstanding every explanation, I think I should look for a way to determine that myself.

Thanks for trying to help.

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