Windows Vista is no small operating system. The additional graphics functionality, search databases and security measures all increase the amount of RAM needed to run a task. Now of course, buying RAM is quite an easy thing to do on a personal basis, but it you have a small business with 20 people to upgrade, perhaps a simpler solution is required.
The Hard Disk - this is the normal solution used by most operating systems when you run out of RAM, but the problem is that hard disks are ssssslllllloooooooooooowwwwww when compared to RAM. This is why "paging" as it is known is such a poor idea except when absolutely necessary.
This of course brings us to ReadyBoost - Vista needs more RAM, you and your customers can not necessarily just go and throw some RAM into each system, especially if it is a Laptop, so how does the USB key help?
Well, we can page through the USB key, meaning that it also acts just like a hard disk for those out of RAM moments. Most sticks and some hard disks can easily do a 40MB/s sustained read thus giving you some speed benefits. USB hard disk sticks are quite performant, which means you might get a performance improvement just from the "reads" from the USB stick versus the hard disks perhaps a 30MB/s vs a 40MB/s type speed, but this is not the killer reason to use the ReadyBoost functionality.
Think about what RAM stands for - Random Access Memory. When does a hard disk fly - when it is streaming a large file, i.e. when it is Sequential access. Paging from a disk often involved moving the head to a location on the disk and then reading an amount of data from the disk into memory. If your hard disk has an 8ms seek time then you are doing well. If we assume that reading takes 0 time, you are still limited to 125 of these operations per second. If each read is accessing just 64KB of memory, the maths works out to be 8MB per second. If the pages being pulled back in are just 4KB in size, the data transfer rate drops to 500KB/s.
Now think about the Random Access capabilites of a USB stick - for many you can not do 40MB/s for pure Random access, but you can get an aweful lot better than a few MB/s. This is the killer feature of ReadyBoost. Infact, the OS thinks about the reads and if it is a big long stream, it may ignore the USB stick and go straight to the hard disk.
For ReadyBoost to work well, ihe USB stick needs to meet certain performance requirements and this is a bit of a problem when at the moment manufacturers do not label the perf of the stick (often because they are hiding something in my personal opinion). There is some great discussion on Tom Archer's blog on this that you are very welcome to read to learn more.
ttfn
David
Posted
Thu, Jul 6 2006 7:08 AM
by
David Overton