Prefetch and SSDs

I doubt that WEI is used to control the setting. WEI is operator controlled--It may or may not be run. My disk scores 7.9 and SF and PF were both set on. One way to tell if SF is doing any good is turn it off for a few days then go check the boot log. You can compare the times. Every boot and shutdown is logged down to the ms. If you look through the history you'll find variations in the boot times as high as a few seconds with no changes at all. In other words, I wouldn't jump to a conclusion one way or the other on 2-3 second changes. A lot will depend on how much your system loads on startup. (Services, desktop and programs)

I forgot to mention: You would think that with a stable system the boot time would be at or near the same or at least within a 100ms. That's not the case. Why is that? Certainly if SF was doing it's job, startup times would be constant. Don't you think?

I believe it is WEI, but MS may determine it some other way. Well, perhaps MS has changed the way they do this, realizing it is just as well on.

SF has nothing to do with boot time, unless you are including pre-loading the programs - which can vary. That is prefetch. Even so, I believe Windows does not always run the same tasks at every boot (maintenance etc) and the boot time is dependent on hardware responses that can vary (disk spin up, wireless network startup, etc). My boot times vary little.

I think there's a bit of confusion on everyone's part. Winsat is what WEI is derived from. You can see the tests in the log. Therefore, WEI = Winsat. Also, Superfetch AND Prefetch BOTH can affect boot (startup). The options for BOTH are exactly the same. They're located in the same Registry section(s).

0 = Do nothing (disable)
1 = Cache applications only
2 = Cache boot files only
3 = Cache everything (default)

OK, tell me how superfetch affects boot startup pleas (sincerely - I would really like to know).

Cluberti is right. Winsat is a command line utility that WEI uses tto create a performance score based on the various results from winsat. They aren't the same thing, but that is splitting hairs.

There's no wear overhead for reads from a SSD. But the fact that Prefetch has to maintain several databases, it adds processor overhead and disk writes. Superfetch uses memory-based indexes and they're NOT carried over to the next boot. They are built for every Windows startup. (And therein lies the processor overhead.)

cluberti said:

What specifically do you want to know? Unless you have a 1st gen SSD, you won't notice the difference on or off. If, however, you do have an older SSD with 1st gen performance, you might. Given that, reducing the fetch hit on disk might be beneficial from a longevity standpoint (and given it makes no difference, setting these to 0 in the registry is a pretty good idea), but if it's on it's not exactly the end of the world either.

I am just curious how things work.

carwiz said:

There's no wear overhead for reads from a SSD. But the fact that Prefetch has to maintain several databases, it adds processor overhead and disk writes. Superfetch uses memory-based indexes and they're NOT carried over to the next boot. They are built for every Windows startup. (And therein lies the processor overhead.)

Not much to add tio today's processors I expect.

I am confused. I thought superfetch loaded frequently used programs into memory when you login, so would save that across boots. Otherwise, what does it do? What do you mean by it uses memory based indices. Indices for what? That does not explain how it works but only, perhaps, one of the mechanisms it uses (for what?)