Don't defrag SSD!!

Reading the OP, I don't understand all the suggestions about turning of FX or SSDs. The OP clearly stated he's using a 1TB 7200RPM regular HDD and his CPU is doing fine. This is very obviously a disk speed issue that is being effectively ameliorated by him upping the disk buffers.
I have no experience with going as high as 150 tracks but I've also had track counts up to a hundred and upping the disk buffer a little can help. The obvious issue you get is that there is a larger delay before you hear anything play. There shouldn't be any significant other drawbacks if everything is doing what it should.
 
If your disk is at least, say, half full, I would also recommend a defrag (leave it overnight as it can take ages on a large disk). Otherwise downmixing subgroups could be a solution. You could also archive your dry guitar tracks. Or even save a version with them and then delete them from the project, save again and continue working. You can always reimport them from an older version if you really need to reamp, but that way at least Sonar won't be reading 20 useless DI'd guitar tracks all the time.

I have run with zero issues at 512 for years and years.  I DO switch ASIO Buffer Size from either 64 or 128 up to 1024 when mixing, and back down to 128 or 64 for tracking/recording.
 
Bob Bone
 

If any of the tracks have lots of short takes, bounce the track to a new track and archive the original.
 
Dan
 

I would agree with some of the replies here.  However the OP mentioned he does not have any synths in his project.  I keep my playback buffer at 1024 and have had pretty stable high track count playbacks.  When Im tracking its not unusual for me to bypass my fx vcia the icon.
 
In my experience with higher track counts - most of it will be bussed down in some fashion... and its a good idea to use alot of foresight when compiling more tracks on top of that.  What I mean is high track counts usually have some doubling, or quad tracking etc...  Ill always use a buss processor instead of each track, and then mix down the buss and archive so the pc only has to play back 1 stereo mix instead of 12 individual tracks, especially if I know during the current tracking session that Ill be adding another high track count ensemble part... such as - "stomps" - or "Claps" - or " gang vocals" which can reach 8 individual tracks or so -   Then... for the final mixdown ill open back up the archives.  Tracking and Mixing are two different stages of the recording process, so its ok to treat them as such and get to know your hardware better, in my opinion all this is.  

dcumpian
If any of the tracks have lots of short takes, bounce the track to a new track and archive the original.
 
Dan
 

Yes. Do this. Except these days you can use the "Flatten" function (which will produce a raw clip inside the original track based on the composite you've created). Then you can clone the track, deselect "Events" in the Clone Dialog (so the track retains all the properties such as FX, panning, levels, routing, etc of the original but does not copy all the takes/clips/lanes) and Ctrl + Shift + (left click) "drag" the flattened clip to the new, empty Clone.
 
So now you've got the exact same track but without all the extra gack/clips/lanes/etc. Just one take/clip.
 
Archive the original (the one with all the takes/clips) and then hide it in the Track Manager so it's completely out of your way. If you want to go back to it just show again in the Track Manager and unarchive it.
 
It's all the separate clips that Sonar needs to keep track of and make available for the Fast Comp procedure (and just general muting/editing/whatever) that causes a lot of disk problems. Think about it... Sonar needs to read ALL that crap and have it at the ready so it seriously burdens the drive.
 
Just like in my last post this method gets you one clip per track. Instead of tons.
 
What I was talking about before in my earlier post is actually a more drastic approach. This "Flatten/Clone/Archive" method is what I usually do after tracking and getting my final edits done. It works very well for getting the project behaving a little better.
 
What I would REALLY like is a Take Lane archiving process to avoid having to Clone and Copy crap.
 
If we could "Archive" the unused takes individually or in a bulk process while leaving our comps alone (in their own lanes in the same track) it would save a ton of time. I actually made a Feature Request about this ages ago.
 
Mayhaps I should find and bump it. Forgot about that one.... lol.
 
Good luck.

I would totally use that. I end up never flattening comps because while I'm doing edits with the performer I'm on the clock and it's always possible I'll need to recomp a bit here and there. If I could flatten and preserve/archive my takes (similar to freezing/unfreezing a softsynth) I would definitely use that option. Or maybe I'm just misunderstanding how this works right now. Fortunately my system doesn't seem to mind too much most of the time.

The originals stay there in a flattened comp.  A new lane is created called Comp.  You can delete that lane and redo the comp and flatten again.

Sanderxpander
I would totally use that. I end up never flattening comps because while I'm doing edits with the performer I'm on the clock and it's always possible I'll need to recomp a bit here and there. If I could flatten and preserve/archive my takes (similar to freezing/unfreezing a softsynth) I would definitely use that option. Or maybe I'm just misunderstanding how this works right now. Fortunately my system doesn't seem to mind too much most of the time.

BobF
The originals stay there in a flattened comp.  A new lane is created called Comp.  You can delete that lane and redo the comp and flatten again.

No need to delete it. I create multiple comps in the same track quite often. I record so many takes when I'm in the "zone" that I usually have a large enough pool to comp together doubled guitar tracks.
 
You just need do some fiddle faddling with the Solo/Mute buttons on the lanes after the Flatten process (which is actually a little anoying but doable).
 
And it doesn't even have to be for doubles. It can just be to have different performances/solos/etc that I can check out later after my brain/ears have settled from tracking.
 
So I'll create Comp 1 and call it C1 in the Notes section of the lane. Then I'll go through and make notes of which sections I used for C1 (sometimes using timecodes or just names I give sections... sometimes I'll use Markers until it's all done and name the markers and use those marker names in my lane notes).
 
Then I'll unsolo the C1 lane (and mute it) and create another comp which I call C2. If I'm creating a double I avoid using the sections I used before for C1 (because otherwise it will dump to mono in the mix and just be louder instead of a double... which is actually a cool effect sometimes in the middle of a solo but not a true double) but if I'm just making an alternate take it doesn't matter what sections get used.
 
You can edit and flattened as many as you want to like this.
 
I've actually gone so far as to create a bunch of comps of all the best material (to get rid of mistakes and stuff I didn't like) then unlocked the comped clips and created a NEW comp from those clips.
 
Kind of like "sifting" the takes to get at the best of the best.
 
It really depends on what I'm doing and how the recording is working out. I roll with a bunch of different weirdo workflows I've concocted based on what I think is gonna work best/save me time.
 
Meh. Kind of "not as designed" usage but I'm a pigheaded bastard so I force things to work how I want.

Virus scanner? Sample rate?