Sorry if these are dumb questions but I'm new to this.  I've thought about
doing this for years and I think I'll finally go ahead and build a new PC system.
I'm willing to splurge for the speed and size of drives for it but I'm not sure
about a few things:
 
  I need one drive for my OS and Calkwalk which I'll use when I record.  The 2nd
drive has samples.  Do I
 
  1. transfer the samples I want to use to the 1st drive to use them or
 
  2. leave samples on the 2nd drive and use the ones I want to use somehow
simultaneously?
 
  (And I guess have a 3rd drive to save audio projects I'm done with and a 4th
drive, a large external drive, for backup storage.)
 
  3. Is the concern for speed (SSD) more a matter of speed during recording or
speed of transferring large or many files from one disk to another?
 
  4. Is there a preference of HHD or SSD regarding one having less glitches than the
other for recording these days?

You don't need to move the samples from the audio HDD to use them in a project.
Samples are most often used by VST plugins - soft synths, drum VSTis etc. - and these programs take care of the streaming of their own samples.
 
As the SSDs are still quite expensive, many use SSDs of moderate size as a system/program drive and big HDDs for audio. Performance wise SSDs are good for anything, but AFAIK their strongest point still today is the reading speed.
The difference in writing isn't that big compared to HDDs. But my knowledge may be outdated. Someone wiser might give more accurate answers.

Kalle is kind of right ,about leaving the libraries on the other HD drive, the plugins will stream or load them into memory...So no need to put them on the boot SSD....if you had a second ssd for those libraries they might be accessed/ load faster, I suppose...
I Would say SSD's are still being updated...although they are more inclined to be more suited for Systems of/with some stability today...They do offer Speed...but in most recording DAWs SSDs were iffy when they first appeared, So they did not support them .
And Because controllers on motherboards may have been lacking support or proper implementation of buffer sizes for large continued writes and reads over long periods of time (as In DAW work) with SSD speeds...glitches happen when bottle necked by the controller on the motherboards...if them controllers were buggy...and some have been..(I am witness)..to cause defects in SSD drives themselves..
 
I think today..those things are moving more into the past, with the newer Motherboards, better controllers that support SSD speeds,...But still, Today I am RMAing a SSD crucial M500...And I just bought it in Dec....So no promises are yet made that they last 1,000,000hrs...if a day....it still is a crap shoot/And same for Hard drives, they do fail...So I believe many will say buy WD Black or Seagate's fastest and most reliable...kind of proven with DAWs and consumer systems, to be sure of some promise of it working without Glitches.
 
If you move to the SSD platform...expect something to go funny some where down the line when mixing both, if using older Motherboards.
 
Just saying it ain't fool proof.
I am where you are going...and I have to test it to make sure it will work.. tomorrow.
 
 

 
  (Until I upgrade, my CPU is older than Kalle Rantaaho's--a socket 939 4800+.)
 
  I got a MIDI Strat and thought of getting a Steinberg UR44.  If I have this
understood right, the samples are loaded into memory, is there an instruction
page or video on recording on my main OS drive while using the Strat with the
samples drive to give the Strat various sounds?

 
  The samples are loaded into memory--32GB is better than 16GB?
 
  (I want to get a whole new system and feel frustrated that Sata Express, DDR4,
and PCIe 4 aren't all going to come out together on a non-e CPU till the one
after Skylake: Cannonlake.)
 

 
 

o