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Readyboost

microsoft.public.windows.vista.performance maintenance






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  #1 (permalink)  
Old 04-09-2007
Thomas - Ungfar.dk
 

Posts: n/a
Readyboost
Hei all..

I have 1GB USB clips. Windows recomand 880mb for readyboost.
What does it do ? Does it ad for RAM og Pagefile ?

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  #2 (permalink)  
Old 04-09-2007
 

Posts: n/a
Re: Readyboost
http://www.microsoft.com/technet/tec...03/VistaKernel

ReadyBoost

The speed of CPUs and memory are fast outpacing that of hard disks, so disks
are a common system performance bottleneck. Random disk I/O is especially
expensive because disk head seek times are on the order of 10
milliseconds-an eternity for today's 3GHz processors. While RAM is ideal for
caching disk data, it is relatively expensive. Flash memory, however, is
generally cheaper and can service random reads up to 10 times faster than a
typical hard disk. Windows Vista, therefore, includes a feature called
ReadyBoost to take advantage of flash memory storage devices by creating an
intermediate caching layer on them that logically sits between memory and
disks.

ReadyBoost consists of a service implemented in
%SystemRoot%\System32\Emdmgmt.dll that runs in a Service Host process, and a
volume filter driver, %SystemRoot%\System32\Drivers\Ecache.sys. (Emd is
short for External Memory Device, the working name for ReadyBoost during its
development.) When you insert a flash device like a USB key into a system,
the ReadyBoost service looks at the device to determine its performance
characteristics and stores the results of its test in
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\Currentversion\Emdmgmt,
seen in Figure 1.


Figure 1 ReadyBoost device test results in the registry (Click the image for
a smaller view)
Figure 1 ReadyBoost device test results in the registry (Click the image for
a larger view)
If you aren't already using a device for caching, and the new device is
between 256MB and 32GB in size, has a transfer rate of 2.5MB/s or higher for
random 4KB reads, and has a transfer rate of 1.75MB/s or higher for random
512KB writes, then ReadyBoost will ask if you'd like to dedicate up to 4GB
of the storage for disk caching. (Although ReadyBoost can use NTFS, it
limits the maximum cache size to 4GB to accommodate FAT32 limitations.) If
you agree, then the service creates a caching file named ReadyBoost.sfcache
in the root of the device and asks SuperFetch to prepopulate the cache in
the background.

After the ReadyBoost service initializes caching, 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. Ecache.sys compresses data and typically achieves a 2:1
compression ratio so a 4GB cache file will usually contain 8GB of data. The
driver encrypts each block it writes using Advanced Encryption Standard
(AES) encryption with a randomly generated per-boot session key in order to
guarantee the privacy of the data in the cache if the device is removed from
the system.

When ReadyBoost sees random reads that can be satisfied from the cache, it
services them from there, but because hard disks have better sequential read
access than flash memory, it lets reads that are part of sequential access
patterns go directly to the disk even if the data is in the cache.


ReadyBoot

Windows Vista uses the same boot-time prefetching as Windows XP did if the
system has less than 512MB of memory, but if the system has 700MB or more of
RAM, it uses an in-RAM cache to optimize the boot process. The size of the
cache depends on the total RAM available, but is large enough to create a
reasonable cache and yet allow the system the memory it needs to boot
smoothly.

After every boot, the ReadyBoost service (the same service that implements
the ReadyBoost feature just described) uses idle CPU time to calculate a
boot-time caching plan for the next boot. It analyzes file trace information
from the five previous boots and identifies which files were accessed and
where they are located on disk. It stores the processed traces in
%SystemRoot%\Prefetch\Readyboot as .fx files and saves the caching plan
under HKLM\System\CurrentControlSet\Services\Ecache\Para meters in REG_BINARY
values named for internal disk volumes they refer to.

The cache is implemented by the same device driver that implements
ReadyBoost caching (Ecache.sys), but the cache's population is guided by the
ReadyBoost service as the system boots. While the boot cache is compressed
like the ReadyBoost cache, another difference between ReadyBoost and
ReadyBoot cache management is that while in ReadyBoot mode, other than the
ReadyBoost service's updates, the cache doesn't change to reflect data
that's read or written during the boot. The ReadyBoost service deletes the
cache 90 seconds after the start of the boot, or if other memory demands
warrant it, and records the cache's statistics in
HKLM\System\CurrentControlSet\Services\Ecache\Para meters\ReadyBootStats, as
shown in Figure 2. Microsoft performance tests show that ReadyBoot provides
performance improvements of about 20 percent over the legacy Windows XP
prefetcher.


Figure 2 ReadyBoot Performance statistics (Click the image for a smaller
view)
Figure 2 ReadyBoot Performance statistics (Click the image for a larger
view)
"Thomas - Ungfar.dk" <none@none.dk> wrote in message
news:OT1YZ6reHHA.1312@TK2MSFTNGP06.phx.gbl...
> Hei all..
>
> I have 1GB USB clips. Windows recomand 880mb for readyboost.
> What does it do ? Does it ad for RAM og Pagefile ?
>


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  #3 (permalink)  
Old 04-09-2007
=?Utf-8?B?TWFyeQ==?=
 

Posts: n/a
RE: Readyboost
Ready Boost is a gimmick that adds almost nothing to Vista. It's supposed to
add virtual memory-- temporary disk space to reduce hard drive usage, but no
one seems to have found that it make any real difference. Save your money for
real ram. I have a 2gb Sandisk Cruzer drive and ready boost make no
difference in memory usage. Use the drives as transfer drives. PS That 880mb
is just a minimum size requirement.

"Thomas - Ungfar.dk" wrote:

> Hei all..
>
> I have 1GB USB clips. Windows recomand 880mb for readyboost.
> What does it do ? Does it ad for RAM og Pagefile ?
>
>

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  #4 (permalink)  
Old 04-09-2007
DevilsPGD
 

Posts: n/a
Re: Readyboost
In message <A503A009-8D7F-4776-9A7D-3C4CDB03D4D8@microsoft.com> Mary
<Mary@discussions.microsoft.com> wrote:

>Ready Boost is a gimmick that adds almost nothing to Vista. It's supposed to
>add virtual memory--


A swing and a miss -- It's a disk cache, not virtual memory.

>temporary disk space to reduce hard drive usage, but no
>one seems to have found that it make any real difference.


Another swing, and again, a miss... I have a laptop here that shows a
very noticeable difference.

You can also see the performance impact on my desktop when running with
limited memory (in other words, when I have a number of virtual machines
open)

>Save your money for real ram.


Finally, a correct answer. However, if additional RAM isn't an option,
and you have a slow hard drive, ReadyBoost is marginally better then
nothing.

>I have a 2gb Sandisk Cruzer drive and ready boost make no
>difference in memory usage.


Nor would it, that's not what it does. ReadyBoost only kicks in when
the in-memory cache misses (and will only be noticeable if ReadyBoost
can service the request substantially faster then your hard drive, which
will typically only happen when the drive is busy)

>Use the drives as transfer drives. PS That 880mb
>is just a minimum size requirement.


Actually, it's not a minimum -- You can run ReadyBoost with less then
880MB of space if you want. The recommendation is a percentage of the
total drive.
--
Insert something clever here.
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  #5 (permalink)  
Old 04-09-2007
AJR
 

Posts: n/a
Re: Readyboost
ReadyBoost also works in concert with ReadyBoot (Yes Virginia there is a
ReadyBoot and ReadyDrive) in that over time it :records file usage and
"slowly" modifies boot time. How "dramatic" the improvement depends on
functions you perfom on the computer - if high page file is being
accomplished - improvement obivious - reading e-mail or surfing - probably
no notice.

Also a ReadyBoost cache is established whether or not you support it with
external memory and why you can insert or remove the external memory device
without loss of data.

"Thomas - Ungfar.dk" <none@none.dk> wrote in message
news:OT1YZ6reHHA.1312@TK2MSFTNGP06.phx.gbl...
> Hei all..
>
> I have 1GB USB clips. Windows recomand 880mb for readyboost.
> What does it do ? Does it ad for RAM og Pagefile ?
>



Reply With Quote
  #6 (permalink)  
Old 04-09-2007
Rock
 

Posts: n/a
Re: Readyboost
"Mary" <Mary@discussions.microsoft.com> wrote
> Ready Boost is a gimmick that adds almost nothing to Vista. It's supposed
> to
> add virtual memory-- temporary disk space to reduce hard drive usage, but
> no
> one seems to have found that it make any real difference. Save your money
> for
> real ram. I have a 2gb Sandisk Cruzer drive and ready boost make no
> difference in memory usage. Use the drives as transfer drives. PS That
> 880mb
> is just a minimum size requirement.
>
> "Thomas - Ungfar.dk" wrote:
>
>> Hei all..
>>
>> I have 1GB USB clips. Windows recomand 880mb for readyboost.
>> What does it do ? Does it ad for RAM og Pagefile ?



Your reply is full of misinformation. ReadyBoost is a cache for random
reads. Yes adding RAM is helpful but it is not always an option. I have a
2GB Sandisk Minicruzer set up for ReadyBoost on one system with 1GB RAM, and
it does improve performance including program loading.

It's fine to say it didn't do anything on your system but don't extend that
to say it doesn't help on all systems.

--
Rock [MS-MVP User/Shell]

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  #7 (permalink)  
Old 04-10-2007
Bill Leary
 

Posts: n/a
Re: Readyboost
"Mary" <Mary@discussions.microsoft.com> wrote in message
news:A503A009-8D7F-4776-9A7D-3C4CDB03D4D8@microsoft.com...
> Ready Boost is a gimmick that adds almost nothing to Vista.
> ((..omitted..))


Not here.

On my system there is a very noticeable reduction in performance when the
Readyboost drive goes offline. Or, if you prefer, a very noticeable
improvement in performance when it's working. I've had two crashes with
Vista, and after each of them the USB drive I have for Readyboost got
switched from being optimized for performance to optimized for quick removal
(I suspect because it got rediscovered). In the "quick removal" mode, it's
performance it too low for Vista to use it as a Readyboost device, and Vista
reverts to normal (non Readyboost) disk usage. The system boots slower and
runs slower.

- Bill

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