ReadyBoost

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ReadyBoost is a component of Microsoft Windows, first introduced with Windows Vista in 2006 and also included with Windows 7. It works by using flash memory, USB 2.0 drive, SD card, CompactFlash or any kind of portable flash mass storage system as a drive for disk cache.

ReadyBoost is also used to facilitate SuperFetch, an updated version of Windows XP's prefetcher which performs analysis of boot-time disk usage patterns and creates a cache which is used in subsequent system boots.[1]

Contents

[edit] Overview

Using ReadyBoost-capable flash memory (NAND memory devices) for caching allows Windows Vista to service random disk reads with performance that is typically 80-100 times faster than random reads from traditional hard drives. This caching applies to all disk content, not just the page file or system DLLs. Flash devices typically are slower than a hard disk for sequential I/O so, to maximize performance, ReadyBoost includes logic that recognizes large, sequential read requests and has the hard disk service these requests.[2]

When a compatible device is plugged in, the Windows AutoPlay dialog offers an additional option to use the flash drive to speed up the system; an additional "ReadyBoost" tab is added to the drive's properties dialog where the amount of space to be used can be configured.[3] 250 MB to 4 GB of flash memory can be assigned. ReadyBoost encrypts, with AES-128, and compresses all data that is placed on the flash device; Microsoft has stated that a 2:1 compression ratio is typical, so that a 4 GB cache could contain upwards of 8 GB of data.[1]

According to Jim Allchin, for future releases of Windows, ReadyBoost will be able to use spare RAM on other networked Windows Vista PCs.[4]

For a device to be compatible and useful it must conform to these requirements:

  • The removable media's capacity must be at least 256 MB—250 MB after formatting. Windows Vista x86 is limited to using 3.5GB (Vista x64 can support up to 16GB); this restriction has been removed in Windows 7.
  • The device must have an access time of 1 ms or less.
  • The device must be capable of 2.5 MB/s read speeds for 4 KB random reads spread uniformly across the entire device, and 1.75 MB/s write speeds for 512 KB random writes spread uniformly across the device.

Other considerations:

  • Vista SP1's ReadyBoost supports NTFS, FAT16 and FAT32. Windows 7 also supports the new exFAT file system. Vista SP2 does not support ReadyBoost for exFAT file system.
  • The initial release of ReadyBoost for Windows Vista supports one device. Windows 7 supports multiple flash drives for ReadyBoost.
  • Microsoft recommends the amount of flash memory for ReadyBoost acceleration be one to three times the amount of random access memory (RAM) in your computer.

Depending on the brand, wear and tear from read-write cycles, and size of the flash memory, the ability to format as NTFS may not be available. Enabling write caching on the flash drive by selecting Optimize for performance in Device Manager allows formatting as NTFS.[5]

ReadyBoost is not available on Windows Server 2008.[6]

[edit] Performance

A system with 512 MB of RAM (the bare minimum for Windows Vista) can see significant gains from ReadyBoost.[7] In one test case, ReadyBoost sped up an operation from 11.7 seconds to 2 seconds (increasing physical memory from 512 MB to 1 GB reduced it to 0.8 seconds).[8]

The core idea of ReadyBoost is that a flash drive has a much faster seek time (less than 1 millisecond), allowing it to satisfy requests faster than a hard disk when booting or reading certain system files. It also leverages the inherent advantage of two parallel sources from which to read data. Unfortunately, USB flash drives are relatively slow for sequential reads and writes, compared to modern desktop hard drives. Desktop hard drives can sustain anywhere from 2 to 10 times the transfer speed of USB flash drives. However, USB flash drives hold an advantage in random access times: typically around 1ms, compared to 12ms and upwards for desktop hard drives.

On laptop computers the performance shifts more in favor of flash memory, laptop memory being priced relatively higher than that for desktop systems, and with many laptops using relatively slow 4200 RPM and 5400 RPM hard drives. Additionally, on a laptop, ReadyBoost caching can reduce hard drive access, allowing the hard drive to spin down for increased battery life.[9] Also, because of the nature of the power management typically enabled during mobile use of a laptop it is a more power efficient way of increasing equipment productivity.

Prior to Vista Service Pack One (SP1), ReadyBoost was quite ineffective when the computer/laptop was put to sleep. ReadyBoost failed to recognize the data in the cache and restarted the caching process when returned from sleep mode. Vista SP1 addresses this problem.[10]

[edit] Note

Since flash drives wear out after a finite (though very large) number of writes, ReadyBoost could eventually wear out the drive it uses—though this may take a long time, depending on various factors. According to Microsoft, the drive should be able to operate for at least ten years.[2]

[edit] See also

[edit] References

  1. ^ a b Mark Russinovich (March 2007). "Inside the Windows Vista Kernel: Part 2". TechNet Magazine. Microsoft. http://www.microsoft.com/technet/technetmag/issues/2007/03/VistaKernel/default.aspx. Retrieved on 2007-03-01. 
  2. ^ a b Archer, Tom; Ayers, Matt (2006-06-02). "ReadyBoost Q&A". Tom Archer's Blog. MSDN Blogs. http://blogs.msdn.com/tomarcher/archive/2006/06/02/615199.aspx. Retrieved on 2008-01-11. 
  3. ^ Tom Archer (April 14, 2006). "ReadyBoost - Using Your USB Key to Speed Up Windows Vista". Tom Archer's Blog. Microsoft. http://blogs.msdn.com/tomarcher/archive/2006/04/14/576548.aspx. Retrieved on 2006-05-21. 
  4. ^ "Jim Allchin". 23 May 2006. http://hive.net/Member/blogs/the_insider/archive/2006/05/23/15378.aspx. Retrieved on 2006-11-01. 
  5. ^ How can I format my USB drive as NTFS?: The Old New Thing
  6. ^ Russinovich, Mark (March 2008). "Inside Windows Server 2008 Kernel Changes". Microsoft. http://technet.microsoft.com/en-us/magazine/cc194386.aspx. Retrieved on 2009-05-10. 
  7. ^ AnandTech: Windows Vista Performance Guide
  8. ^ AnandTech: Windows Vista Performance Guide
  9. ^ AnandTech: Investigating Intel's Turbo Memory: Does it really work?
  10. ^ Vista SP1 will fix critical ReadyBoost performance bug

[edit] External links

[edit] Microsoft links

[edit] Other links

Retrieved from "http://en.wikipedia.org/wiki/ReadyBoost"
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