Is It ReadyBoost-Capable?
ReadyBoost is a new technology. It is literally still a work in progress. As such, there are a few requirements and limitations that control its use. Let's take a look.
• Only one flash memory device can be used at any one time
• USB flash drives
|Devices Not Supported||
• External card readers
|Minimum Size||• 256MB capacity with at least 235 MB of free space|
|Maximum Size||• ReadyBoost supports
up to 4 GB of storage (8 GB after compression)
• Devices with greater capacities can only allocate up to 4 GB to ReadyBoost
|File Systems Supported||• NTFS
|Performance Limitations||• The device should
have a random access time of 1 ms or less
• The device must be capable of 4 KB random reads across the entire device capacity at speeds of 2.5 MB/s or faster
• The device must be capable of 512 KB random writes across the entire device capacity at speeds of 1.75 MB/s or faster
As you can see, ReadyBoost has some pretty specific requirements for flash memory devices. That's why not every flash memory device in the market supports ReadyFlash. The most problematic issues are the random read and write speeds.
Most flash devices, especially USB flash drives, are designed for fast sequential transfers. Even high-end USB flash drives that deliver incredibly high transfer rates may not even be ReadyBoost-capable. Take a look at read and write speeds of some USB flash drives in the market today.
As you can see, most of the USB flash drives in this comparison have very high sequential read speeds. Performance-leaders like the OCZ Rally drives are capable of sequential read speeds 15-16 MB/s. Yet, these fast flash drives choke badly at random 4 KB reads. They only managed absymally poor random read speeds of only 60 KB/s to 110 KB/s.
In contrast, new ReadyBoost-capable flash drives like the Kingston DataTraveler ReadyFlash and GoldenMars GeeDom do much better at random 4 KB reads. Even the slowest ReadyBoost-capable drive, the GeeDom is at least 8X faster at random reads than the fastest non-ReadyBoost drive.
Do note that our tests may be a lot stricter than the Windows Vista's built-in test. They did dictate a minimum random 4 KB read speed of 2.5 MB/s. But while the GeeDom only managed 0.88 MB/s, it actually passed Windows Vista's ReadyBoost test. Now, let's take a look at write speeds.
Again, random writes are slower than sequential writes, albeit with a much smaller gap than what we saw in the read tests. As far as writes are concerned, Microsoft specified a minimum random 512 KB write speed of 1.75 MB/s but that's easily attained by every USB flash drive we tested. In fact, they were all capable of much higher random write speeds.
Therefore, it appears that the random read speed is really the only issue affecting the qualification of flash memory devices for ReadyBoost. Microsoft is working with flash memory companies to identify ReadyBoost-capable devices. However, it remains to be seen whether this will turn out to be nothing more than a marketing exercise like Microsoft's Certified for Windows Vista program.
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