How does a cluster size affect the readyboost function? The default cluster size is 2^12 bytes. What about higher order? I think of 2^13 bytes or 2^14 bytes? What is better ExFat or NTFS for ReadyBoost?


Larger cluster size will be better, but will mean more wasted space. It might also help to have the driver formatted as ExFAT.

A larger cluster size means that more data can me read/written from the drive at the same time, increasing speed.

  • Wouldn't the best speed be the block size of the card read that accesses the drive? e.g. if it reads in 24k chunks for example, then setting it to 32k clusters would require two reads. I wonder how one can work out the block size that the device reads from natively? – David d C e Freitas Mar 30 '14 at 7:29

I started testing cluster size and I found that for my 8Gb thumb drive the best format was Exfat at 4096Kb. I tested with DiskMark. Speedgain at 8192Kb was negligible but there was gain over 2048Kb cluster size.

Sequential Read (Q= 32,T= 1) : 19.295 MB/s Sequential Write (Q= 32,T= 1) : 7.864 MB/s Random Read 4KiB (Q= 32,T= 1) : 5.673 MB/s [ 1385.0 IOPS] Random Write 4KiB (Q= 32,T= 1) : 0.015 MB/s [ 3.7 IOPS] Sequential Read (T= 1) : 19.084 MB/s Sequential Write (T= 1) : 7.968 MB/s Random Read 4KiB (Q= 1,T= 1) : 5.321 MB/s [ 1299.1 IOPS] Random Write 4KiB (Q= 1,T= 1) : 0.010 MB/s


If you whant to get the advantages of ReadyBoost on Windows 7, you have to do the following:

  1. Format the external disk with exFAT, with cluster size 1024kb.
  2. Go to drive Properties (right click on the drive letter) and select ReadyBoost Tab.
  3. Select Dedicate this drive to ReadyBoost. Apply.
  4. Go to Customize Tab and Optimize for General Items. Apply and Ok.

Then the system will create the ReadyBoost file.

If you run virtual machines, configure their preferences to "allow some VM swap memory".

From: Limitations on Windows 7 ReadyBoost?

  • Thanks, but will it really be better than using HDD swap file? I could buy 8GB flash card now best for low access times and put it in card reader leaving it there but would it really be worth it? You know even though i have 8GB of RAM on my laptop, i still get my HDD slowed down like turtle which interrupts my work, takes time to wait etc. – Boris_yo Apr 16 '12 at 14:58
  • @Boris_yo you always need a swap file. ReadyBoost is not the same as the swap file. Usually laptops came with low-speed HDDs (5.400rpm) so try to buy one of 7.200rpm. And use a very-fast flash drive: about 20mb/s write and more for read speed. – JoanComasFdz Apr 16 '12 at 15:31
  • Why i cannot move swapfile to flash drive so no HDD will be used almost? – Boris_yo Apr 16 '12 at 16:32
  • Because the swap file has a high range of write/read and the flash memory has a limited count of times a cell can be writted. – JoanComasFdz Apr 16 '12 at 17:05
  • 1
    Yes, it is. But I'm not sure how a swap file will begave in a FlashDrive. And ReadyBosst is not a Swap file. You can try to move the swap to the Flash drive and test it. Then repeat the tests with the swap file in its default place and with ReadyBoost enabled. This way you can decide wich performance is better for you. – JoanComasFdz Apr 16 '12 at 17:14

Cluster size does not really matter for ReadyBoost: it uses one big file, and all writes and reads are done directly and aligned to the memory page size regardless of file cluster size.

The only thing that matters is that the start of the file is aligned to the sector size used for communication with the drive, so 4kB or a multiple of such for cluster size is recommended. This will almost always be the case anyway.

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