New I/O Features

One set of features we have held off on discussing in-depth until now have been the I/O related features in Vista, including ReadyBoost, ReadyDrive, SuperFetch, and the new networking stack. We'll get to the new networking stack in a bit, but first the Ready features and SuperFetch merit a bit of discussion.

SuperFetch

Depending on the scenario, a great deal of computing time is spent waiting for data retrieval due to processors being significantly faster than the mass storage devices. To that extent modern computers have a hierarchy of several levels of data caches to store and manipulate data, ranging from registers and L1 cache down to hard drives and their own cache. This system of cache layers works very well in hiding the speed differences between various layers, but there are still large gaps between places such as the CPU and RAM, and RAM and hard drives. One possible improvement - and certainly the most effective solution that Microsoft has implemented in Vista - is to try to move up required data to a higher layer, in this case by keeping more data in RAM than just the bare minimum.

The result of this is the first I/O improving technology, SuperFetch, a new technology designed to cache as much data as RAM space allows. Previously, Windows XP had a more basic implementation of this idea called prefetch, which used trace logs of programs loading in order to help XP optimize the loading sequence. SuperFetch in turn takes things a step further by not only figuring out what data is required to launch an application, but it actually loads this data into memory as space allows so that if it's needed at a later point the data is already in RAM instead of still residing on the hard drive.

In practice, SuperFetch depends a great deal on how predictable a user is and how much extra RAM a computer has. Veteran computer users will be slightly dismayed at first to find that Vista is actively attempting to use the entirety of a computer's RAM (down to 0MB of free memory remaining), which is effectively the opposite of how XP attempted to conserve as much memory as possible. This looks worse than it actually is, as cached data can immediately be thrown away to make space for an application as required, but Microsoft has nonetheless attempted to clarify things since Beta 2 where the Task Manager would only show total memory usage. Now the Task Manager makes it clear how much RAM is being used for program execution and how much is being used for cache, but this will still inevitably spark a few debates on if full RAM usage is really a good thing. Given that RAM tends to be a low power device operating at near full power all the time (especially on desktop machines), we feel RAM is the ideal underutilized component to try to fully exploit, as it doesn't incur the extra power costs of running at full load like a CPU/GPU do.


However as we mentioned previously, the total benefit is dependent in predictability and excess RAM. As SuperFetch is designed to predict what applications a user may load next and then pre-load them into cache (i.e., a user loads Outlook at 10am every day), it works better for users with routines than those without. Similarly, as Vista attempts to use all RAM for the cache, it can always benefit from more RAM to keep more things cached (a behavior similar to MacOS X).

Index How Much RAM?
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  • Ryan Smith - Saturday, February 03, 2007 - link

    That's up to Vista, it benchmarks a flash drive to make sure it's fast enough to be effectively used as a ReadyBoost cache. If ReadyBoost won't engage, then your drive isn't passing one(or more) of their tests. Reply
  • mlambert890 - Friday, February 02, 2007 - link

    How is the PC hemmhoraging marketshare to the Mac? You've got to be kidding. Their marketshare in 06 rose from a pathetic 4.4 to a somewhat less pathetic 4.8. Thats with ALL of their ridiculous hype, ALL of the asskissing from the press (including you guys now I guess?) and ALL of the armies of lunatic "Mac priests" that pollute every forum.

    Its hillarious that you would position this tiny growth in a share that declined steadily for 22 years until it hit rock bottom at like 3% in 2003 as a "hemmhorage". I have to wonder why you would characterize it that way. To be honest, it reeks of bias.
    Reply
  • quanta - Friday, February 02, 2007 - link

    Think about it, ReadyBoost is treated by Vista as random access memory, to store temoprary contents than can change very often. Considering typical USB flash drive only has 100k write cycle, you will need to replace it very soon. Worse yet, when the flash drive is gone, so will your critical data at the worst possible time. With the hardware requirement of Vista, no amount of wear levelling is going to help. Reply
  • Ryan Smith - Friday, February 02, 2007 - link

    No, this is wrong.

    ReadyBoost is a write-through data cache handled by the SuperFetch system; when enabled SuperFetch uses it as another cache location optimized for small files. Based on the information we've seen, it's used primarily to store DLLs and other static and semi-static data that is needed an intermediate amount of time(not important enough to spend valuable RAM, important enough to cache), with highly dynamic data sent to SuperFetch or the hard disk to avoid unnecessary wear out. It will most certainly put wear on flash memory, but it seems unlikely that it will put 51TB of write-wear(the amount of data that needs to be written on a 512MB flash card to write over all bits 100k times) before several years out.

    Of course, this is as according to Microsoft. We don't really know what exactly is being stored on a ReadyBoost drive at any given moment, however we have no reason to believe that Microsoft isn't really taking efforts to minimize writes. We'll find out if/when flash memory starts wearing out.
    Reply
  • mlambert890 - Friday, February 02, 2007 - link

    We'll see. Please remember that the 100k write cycle is an average, that the flash is used as a small cache only, and that write leveling of COURSE will help before making assumptions.

    Ive been beating up flash for YEARS thats still going. There are moves to literally put OS's on flash based hard drives. Hybrid drives already use the same concept as ReadyBoost (and are also supported on Vista).

    Using flash as a cache for magnetic media is not some untested concept that is going to lead to global data destruction.

    MS must have really destroyed their mindshare that so many armchair scientists are just fully willing to believe that theyve figured out ALL the stuff that the "idiots" in Redmond dont realize. Give a little credit to the armies of PhDs that work on at least the basic concept for this crap. Maybe implementation gets flawed by the realities of release cycles and budgets, but BASIC CONCEPT is typically sound.
    Reply
  • dugbug - Friday, February 02, 2007 - link

    UAC is like a firewall -- chatty at first (during installs and configurations), but once you have set up your system you will hardly ever hear from it. This should be obvious to the authors.

    And for that matter, the 6-operation file delete they discuss in the beginning was for deleting a file on a shared desktop (meaning a delete was for all users). This is commonplace for enterprise and workplace users, it should be no surprise that a file used by others would require permissions to delete. Though Im glad the number of operations was greatly reduced.

    As to the comments about vista being sluggish? Perhaps it is RAM? I have 2Gb and vista runs without any slowdown at all. Once you use it for a while you won't go back to XP.

    -d
    Reply
  • LoneWolf15 - Friday, February 02, 2007 - link

    Untrue. Enthusiasts use lots of things like the Control Panel, MMC console, etc. and these all require UAC every time. Currently, I also have startup programs on my beta-test box that UAC blocks. This would be fine, if UAC had a feature saying "Yes, I know what this program is, let it run every time all the time" and be done. But, UAC doesn't have this option, so a user has to allow the program to run every single freaking time they boot their machine.

    I've tried changing the program properties so that it runs as Administrator; that hasn't solved the problem. I turned off UAC, which gives me a lovely annoying red-X shield in the system tray that every so often decides to warn me with a popup balloon that UAC is turned off and I could be in danger, so it's annoying even when turned off, and there's no easy way around it. Enthusiasts do a lot with their computers, and what they do is likely to increase their number of UAC prompts. Bottom line: Unlike OS X's methods, Vista's UAC happens far more often, and is far more annoying. And because it doesn't require a password (like OS X) and is just a click-through, I'll put money down that within a year, it will be worthless, as the average user will learn to click through it without reading a single bit of info.
    Reply
  • funk3y - Sunday, February 04, 2007 - link

    The red cross can also be disabled for sure; on my computer, which is a member of a domain I recieve no error message at all, even if UAC & co are disabled. Reply
  • haplo602 - Friday, February 02, 2007 - link

    Realy. What's the hype all about ?

    SuperFetch - trivial change to caching mechanisms. Anybody that would require it would have already implemented it in *NIX systems. This is a purely desktop user feature to hid some processing overhead. There's nothing new about this that would prevent implementation in w2k already except MS incompetence ...

    ReadyBoost - So the new standard is to have a permanently attached USB stick to have some performance ?

    Compund TCP, Receive window auto tuning - I laughed like mad. So they finaly made a proper implementation of something network related? End even then Vista is SLOWER. I'd suggest take a stand-alone NIC that Vista nad XP have drivers for themselves and test it. Should rule out driver bugs.

    I/O improvements - so I make an app that makes a high priority high capacity I/O operation (say 1GB) and you can go for lunch till the system is anyway usable. Seriously. I/O in small chunks makes perfect sense in multitasking environments since you have more entry point and can adjust the stream on OS level and tune performance. That XP or Vista are stupid enough to do this is their fault. I guess MS will hype this as the next best thing in a future OS ?

    All in All every feature hyped in the article does not deserve a Marketing Name(tm) because it is a normal concept. So we have a shiny new bigger and slower OS that is hiding this behind hyped features. F.E. memory compression could very much improve system performance without relying on external devices (ReadyBoost).
    Reply
  • mlambert890 - Friday, February 02, 2007 - link

    Just admit your bias man. There is NOTHING MS could do that would cause you to give them kudos. I spend my days arguing with guys like you for a living (unfortunately) and its just exhausting.

    I could point you to REAMS of documentation of all the crap that has been rewritten and overhauled in Vista, but whats the point? You want to hate it so hate it.

    Its sad that technology debates are STILL religion for so many after all this time :(
    Reply

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