ReadyBoost: Difference between revisions

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'''ReadyBoost''' (codenamed '''EMD'''<ref name="FeatureNames">{{cite web |url= |title=SuperFetch, ReadyBoost and ReadyDrive: some new feature names for you |last=Moulster |first=Ian |date=April 6, 2006 |publisher=[[Microsoft]] |work=MSDN Blogs |accessdate=July 11, 2015}}</ref>) is a [[cache (computing)|disk caching]] software component developed by [[Microsoft]] for [[Windows Vista]] and included in later versions of the [[Windows (operating system)|Windows]] [[operating system]]. ReadyBoost enables [[flash memory|NAND memory]] [[mass storage]] devices, including [[CompactFlash]], [[Secure Digital card|SD card]]s, and [[USB flash drive]]s, to be used as a [[cache (computing)|write cache]] between a [[hard drive]] and [[random access memory]] in an effort to increase computing performance. ReadyBoost relies on the [[Windows Vista I/O technologies#SuperFetch|SuperFetch]] technology and, like SuperFetch, adjusts its cache based on user activity. Other features, including [[Windows Vista I/O technologies#ReadyDrive|ReadyDrive]], are implemented in a manner similar to ReadyBoost.<ref name="KernelChanges">{{cite web |url= |title=Windows Vista Kernel Changes |last=Russinovich |first=Mark |authorlink=Mark Russinovich |date=2007 |publisher=[[Microsoft]] |archiveurl= |archivedate=September 12, 2007 |format=PPTX |accessdate=July 12, 2015}}</ref>
== Overview ==
Using ReadyBoost-capable flash memory ([[NAND flash|NAND memory]] devices) for caching allows [[Windows Vista]] and later to service random disk reads with better performance than without the cache. This caching applies to all disk content, not just the page file or system DLLs. Flash devices typically are slower than a mechanical 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.<ref name="QnA">{{cite web|url= |title=ReadyBoost Q&A |accessdate=2008-01-11 |last=Archer |first=Tom |author2=Ayers, Matt |date=2006-06-02 |work=Tom Archer's Blog |publisher=[[MSDN Blogs]] }}</ref>
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.<ref name="readyboostJim Allchin">{{cite web |url= |title=ReadyBoost - Using Your USB Key to Speed Up Windows Vista |date=April 14, 2006 |accessdate=2006-05-21 |author=Tom Archer |work=Tom Archer's Blog |publisher=Microsoft}}</ref> The minimum cache size is 250&nbsp;MB. In Vista or with FAT32 formatting of the drive, the maximum is 4&nbsp;GB. In Windows 7 with NTFS or exFAT formatting, the maximum cache size is 32&nbsp;GB per device. Windows Vista allows only one device to be used, while Windows 7 allows multiple caches, one per device, up to a total of 256&nbsp;GB.<ref name="readyboostMarius Oiaga">{{cite web |url= |title=Windows 7 RTM ReadyBoost 256 GB of Memory Cache Support |date=October 12, 2009 |accessdate=2013-01-09 |author=Marius Oiaga |work=SOFTPEDIA |publisher=SoftNews NET SRL}}</ref>
* The device must have an access time of 1&nbsp;ms or less.
* The device must be capable of 2.5&nbsp;MBMbit/s read speeds for 4&nbsp;kB random reads spread uniformly across the entire device, and 1.75&nbsp;MBMbit/s write speeds for 512&nbsp;kB random writes spread uniformly across the device.<ref name="is-your-flash-drive-fast-enough">{{cite web
|title=Is your flash drive fast enough for Vista's ReadyBoost?
Other considerations:
* Vista's ReadyBoost supports [[NTFS]], [[File Allocation Table|FAT16, and FAT32]] from SP1 onwards. [[Windows 7]] also supports the newer [[exFAT]] file system. As the ReadyBoost cache is stored as a file, the flash drive must be formatted as FAT32, NTFS, or exFAT in order to have a cache size greater than FAT16's 2&nbsp;GB filesize limit; if the desired cache size is 4&nbsp;GB (the FAT32 filesize limit) or larger, the drive must be formatted as NTFS or exFAT. The performance differences between these file systems are negligible with ReadyBoost.
* The initial release of ReadyBoost for Windows Vista supported one device. Windows 7 supports multiple flash drives for ReadyBoost, so performance improvement similar to [[RAID#Standard levels|RAID&nbsp;0]] can be expected.
* The ReadyBoost algorithm was improved in Windows 7, resulting in better performance. One experiment showed reading of flash memory up to 5–10 times faster than Windows Vista due to higher hit rate.{{Citation needed|date=August 2012}}
* Because ReadyBoost stores its cache as a file on the root directory of the drive rather than using the flash memory without a file system, the file system must be [[Mount (computing)|mounted]] and [[Drive letter assignment|assigned a drive letter]]. The ReadyBoost cache is created on the [[Root directory#Multiple root directories|root directory]] of the drive.
* If the system drive (the primary drive, with Windows system files on it) is a solid-state drive (SSD), ReadyBoost is disabled, since reading from that drive would be at least as fast as reading from the ReadyBoost drive.<ref name=understand>{{cite journal|magazine=[[TechNet Magazine]]|url=|title=Understand ReadyBoost and whether it will Speed Up your System|publisher=Microsoft|accessdate=2012-12-14}}</ref>
* ReadyBoost caches all data as it is being written to the local hard disk: "the Ecache.sys device driver intercepts all reads and writes to local hard disk volumes (C:\, for example), and copies any data being written into the caching file that the service created."<ref name="russinovich"/> [[Windows Vista I/O technologies#SuperFetch|SuperFetch]] pre-populates frequently-read data into ReadyBoost cache, so SuperFetch is necessary for ReadyBoost to perform well.<ref name="robbiebench">{{cite web|title=ReadyBoost - Robbie's Benchmark|url=|date=14 April 2012|accessdate=17 October 2014}}</ref>
ReadyBoost is not available on [[Windows Server 2008]].<ref>{{cite web
A system with 512&nbsp;MB of RAM (the minimum requirement for Windows Vista) can see significant gains from ReadyBoost.<ref>[ AnandTech: Windows Vista Performance Guide<!-- reflinks title -->]</ref><ref>Schmid, Patrick. [,1532-6.html "Windows Vista's SuperFetch and ReadyBoost Analyzed:] Conclusion." Toms Hardware. 2007-01-31.</ref> In one test case, adding 1&nbsp;GB of ReadyBoost memory sped up an operation from 11.7 seconds to 2 seconds. However, increasing the physical memory (RAM) from 512&nbsp;MB to 1&nbsp;GB (without ReadyBoost) reduced it to 0.8 seconds.<ref>[ AnandTech: Windows Vista Performance Guide<!-- reflinks title -->]</ref> System performance with ReadyBoost can be monitored by Windows Performance Monitor.<ref>Schultz, Greg. [ "Keep tabs on ReadyBoost with Windows 7's Performance Monitor."] ''TechRepublic.'' 2010-03-24.</ref> As the price of RAM decreased and more RAM was installed in computers, the mitigations provided by ReadyBoost to systems with insufficient memory decreased.
The core idea of ReadyBoost is that a [[flash memory]] (e.g. a [[USB flash drive]] or an [[Solid-state drive|SSD]]) have a much faster seek time than a typical magnetic hard disk (less than 1&nbsp;ms), allowing it to satisfy requests faster than reading files from the hard disk. It also leverages the inherent advantage of two parallel sources from which to read data, whereas Windows 7 enables the use of up to eight flash drives at once, allowing up to nine parallel sources. [[Universal Serial Bus#USB 2.0|USB 2.0]] flash drives are slower for ''sequential'' reads and writes than modern desktop hard drives. Desktop hard drives can sustain anywhere from 2 to 10 times the transfer speed of USB 2.0 flash drives but are equal to or slower than [[USB 3.0]] and [[IEEE 1394 interface|Firewire (IEEE 1394)]] for sequential data. USB 2.0 and faster flash drives have faster ''random access'' times: typically around 1&nbsp;ms, compared to 12&nbsp;ms for mainstream desktop hard drives.<ref>{{cite web | date = June 2010 | url = | title = WD Scorpio Blue Mobile: Drive Specifications | publisher = [[Western Digital]] | accessdate = 15 January 2011 | deadurl = yes | archiveurl = | archivedate = 5 January 2011 | df = }}</ref>
<!-- High-cost ($500-$20,000) solid state mass storage currently has random sustained external throughput up to 3&nbsp;GB/s (TMS RamSan) and latency as low as 0.003 ms (Violin 1010).<ref>[ the Fastest Solid State Disks (SSDs) 1.8&quot;, 2.5&quot; to 3U]</ref>
* [ Channel9 interview with Michael Fortin on ReadyBoost and other performance technologies in Windows Vista]
* [ Section STORAGE-009 in Windows Logo Program Requirements Suite, Version 3.09]
* [ Understand ReadyBoost and whether it will Speed Up your System]
* [ Microsoft's Software Patent on ReadyBoost]
* [ AnandTech: Windows Vista Performance Guide - ReadyBoost, ReadyBoost Performance Analysis, and Hard Drive Performance and ReadyBoost]