Windows
ReadyBoost
Windows
ReadyBoost
improves system memory and boosts performance.
Adding system memory
(typically referred to as RAM) is often the best way to improve a PC's
performance, since more memory means more applications are ready to run without
accessing the hard drive. However, upgrading memory can be difficult and
costly, and some machines have limited memory expansion capabilities, making it
impossible to add RAM.
Windows Vista introduces
Windows ReadyBoost,
a new concept in adding memory to a system. You can use non-volatile flash
memory, such as that on a universal serial bus (USB) flash drive, to improve
performance without having to add additional memory "under the hood."
The flash memory device
serves as an additional memory cache—that is, memory that the computer can
access much more quickly than it can access data on the hard drive. Windows ReadyBoost
relies on the intelligent memory management of Windows
SuperFetch and can significantly improve system
responsiveness.
It's easy
to use Windows ReadyBoost.
When a removable memory device such as a USB flash drive or a secure digital
(SD) memory card is first inserted into a port, Windows Vista checks to see if
its performance is fast enough to work with Windows ReadyBoost. If so, you
are asked if you want to use this device to speed up system performance. You
can choose to allocate part of a USB drive's memory to speed up performance and
use the remainder to store files.
FAQ:
Q:
What perf do you need on your device?
A: 2.5MB/sec throughput for 4K random reads and 1.75MB/sec throughput for 512K
random writes
Q: My device says 12MB/sec (or 133x or something
else) on the package but windows says that it isn't fast enough to use as a ReadyBoost
device... why?
A: Two possible reasons:
- The numbers measure sequential performance and we
measure random. We've seen devices that have great sequential perf, but horrible random
- The performance isn't consistantly
fast across the entire device. Some devices have 128M of lightning fast
flash and the rest of the device is really slow. This is fine for some
applications but not ReadyBoost.
Q: What's the largest amount of flash that I can use for ReadyBoost?
A: You can use up to 4GB of flash for ReadyBoost (which
turns out to be 8GB of cache w/ the compression)
Q: Why can't I use more than 4GB of flash?
A: The FAT32 filesystem limits our ReadyBoost.sfcache
file to 4GB
Q: What's the smallest ReadyBoost cache that I can use
A: The smallest cache is 256MB (well, 250 after formatting). Post beta2, we may
drop it another 10 MB or so.
Q: Ok... 256M-4GB is a pretty big range... any recommendations?
A: Yes. We recommend a 1:1 ratio of flash to system memory at the low end and
as high as 2.5:1 flash to system memory. Higher than that and
you won't see much benefit.
Q: Isn't this just putting the paging file onto a flash disk?
A: Not really - the file is still backed on disk. This is a cache - if the data
is not found in the ReadyBoost cache, we fall back to the HDD.
Q: Aren't Hard Disks faster than flash? My HDD has 80MB/sec throughput.
A: Hard drives are great for large sequential I/O. For those situations, ReadyBoost
gets out of the way. We concentrate on improving the performance of small,
random I/Os, like paging to and from disk.
Q: What happens when you remove the drive?
A: When a surprise remove event occurs and we can't find the drive, we fall
back to disk. Again, all pages on the device are backed by a page on disk. No
exceptions. This isn't a separate page file store, but rather a cache to speed
up access to frequently used data.
Q: Isn't user data on a removable device a security risk?
A: This was one of our first concerns and to mitigate this risk, we use AES-128
to encrypt everything that we write to the device.
Q: Won't this wear out the drive?
A: Nope. We're aware of the lifecycle issues with flash drives and are smart
about how and when we do our writes to the device. Our research shows that we
will get at least 10+ years out of flash devices that we support.
Q: Can use use multiple devices for EMDs?
A: Nope. We've limited
Q: Why just one device?
A: Time and quality. Since this is the first revision of the feature, we
decided to focus on making the single device exceptional, without the
difficulties of managing multiple caches. We like the idea, though, and it's
under consideration for future versions.
Q: Do you support SD/CF/memory stick/MMC/etc.?
A: Mostly. In beta2, we added support for a small number of SD/CF cards on
internal USB2 & PCIe busses. RC1 has a much
broader support range.
Q: Why don't you support SD on my USB2.0 external card reader?
A: We unfortunately don't support external card readers - there were some
technical hurdles that we didn't have time to address. In general, if a card
reader shows a drive without media in it (like a floppy drive or CD ROM does), we can't use it for ReadyBoost.
Q: Will it support all USB drives, regardless of how they are ID'd to the OS ("hard disk drive" or "Device
with Removable Storage")?
A: We have no way to tell what is on the other end of a USB cable so we do some
basic size checks (since no one has a 200GB flash device ;-) ) and then perform
our speed tests. HDD will not, however, pass our speed tests, and there is no
benefit to using a USB HDD for ReadyBoost.
Q: Can you use an mp3 player to speed up your system?
A: Not currently. MP3 players use the 'plays for sure' interfaces to expose
themselves to Windows. We require that the device appear as a disk volume.
These aren't currently compatible.
Q: How much of a speed increase are we talking about?
A: Well, that depends. On average, a RANDOM 4K read from flash is about 10x faster than from HDD. Now, how does that translate to
end-user perf? Under memory pressure and heavy disk
activity, the system is much more responsive; on a 4GB machine with few
applications running, the ReadyBoost effect is much less noticable.
Q: I can't get my device to work with ReadyBoost... can I lower
the perf requirements?
A: Unfortunately, no. We've set the perf requirements
to the lowest possible throughput that still makes your system faster. If we
lowered the perf requirements, then there wouldn't be
a noticeable benefit to using ReadyBoost. Remember, we're not adding
memory, we're improving disk access.
Q: Which manufacturers support ReadyBoost?
A: Well, I hope that all of them do, eventually. Right now, we're working with
manufacturers to create a program that will allow them to identify ReadyBoost
capable devices on their packaging.