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I've brought an 4GB SD card and I'm dedicating it for use by ReadyBoost (on Windows7)

Im looking to get the most profit on performance, so i've formatted it with exFAT (as recommended by Microsoft) but I have some doubts to define what best .Allocation Unit Size* I should choose.

Since I can't get how ReadyBoost/SD card exactly read/seek the data, can someone tell what make choosing an Allocation Unit Size in favor of another for this scheme ?

Apparently, ReadyBoost is allocating all the free space in SD card as one huge file, so a big Allocation Unit Size is advised for fastest reading time. I'm not confusing with ordinary HDD's ?

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How much memory do you have in your system? Readyboost is only really of use in memory starved systems that have 1GiB or less of RAM... –  Mokubai Jun 13 '10 at 18:13
Using ReadyBoost-capable flash memory for caching allows Windows 7 and Vista to service random disk reads with performance that is typically 80-100 times faster than random reads from traditional hard drives.-from wikipedia. to not confuse with "paging files" ... nothing to do with the memory –  user8228 Jul 15 '10 at 0:11
Can you link to where Microsoft recommends exFAT for ReadyBoost? –  endolith May 6 '11 at 4:38

3 Answers 3

It is not useless at all. I use it all the time.

It helps when you have low RAM or a slow HDD (5400-7200RPM). Apps start and things load much, much faster. Be sure to enable "high performance" mode for the readyboost USB devices, in order to get the most out of it.

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How do you enable "high performance" mode? –  endolith May 6 '11 at 4:39

I would use exFAT, it has slightly bit better performance than the others and will also allow you to use more then 4 GB of space for ReadyBoost.

For the allocation unit size, I belive 4 kB will work the best but I could be wrong. This is the size of the chuncks that ReadyBoost uses and it will give you the best performance for ReadyBoost.

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According to this SevenForums page, "if you're going to use the drive exclusively for readyboost, try out exFAT with 32 mb allocation unit size."

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Whilst this may theoretically answer the question, it would be preferable to include the essential parts of the answer here, and provide the link for reference. –  Mokubai Jan 17 at 18:03

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