What causes excessive writes to SSD on macOS?

[ProQuiz]

I've had my MacBook Pro powered on for 2 days and 7 hours and I've done nothing "out of the ordinary" in terms of installing or downloading anything. I've been browsing the Internet mostly with Safari. If I check Activity Monitor, it says that I have 33 GB of reads and 44 GB of writes. Why are the writes so high when I haven't even been doing any "writing" to the SSD other than just browsing the Internet with Safari? Isn't this going to cause excessive wear to the SSD?

 

[saudor]

web browsers are pretty chatty when it comes to writes to the SSD. 44gb over two days is fine. I'm hitting 30gb per day

Unless you're using heavy swap and absolutely pounding the SSD due to lack of RAM, the SSD will outlive the machine.

2011 256gb SSDs that were 2 bit MLC and no 3D nand could do 2000 TB before dying (these were rated around 75TB). Modern SSDs are rated at 300 TB per 500gb of space so even at that, that's still 15,000 days.

 

[Ben J.]

Just checked my r/w numbers in Activity Monitor;
78 hours since last restart.
470GB write, 280GB read.
Mostly browsing and streaming hours and hours of sports etc.
Firefox had 280 w and 10 r.

I'm not worried, and I don't think the OP should be either.

I have excuded the Library/Cache folder from my backups, btw. For this reason. No need to backup caches. Cashes will be rebuilt.

 

[Fishrrman]

OP:
How much RAM do you have?

VM disk swapping is almost certainly "the problem".
It's been this way going all the way back to "Mavericks" (which changed the basic way the OS handles RAM).

I SOLVED the problem of "excessive disk writing", but "my way" is controversial in this forum.
I used terminal to DISABLE VM disk swapping, so the OS CAN'T do it.

But...
You have to have enough RAM for everything to "exist" in live RAM
and
You have to be aware of how much stuff (apps, etc.) you have open, so as not to "push too far".

Having said that,
Since I started doing this, YEARS ago now, I haven't had any memory-related crashes.
It works for me.

 

[ProQuiz]

OP:
How much RAM do you have?

VM disk swapping is almost certainly "the problem".
It's been this way going all the way back to "Mavericks" (which changed the basic way the OS handles RAM).

I SOLVED the problem of "excessive disk writing", but "my way" is controversial in this forum.
I used terminal to DISABLE VM disk swapping, so the OS CAN'T do it.

But...
You have to have enough RAM for everything to "exist" in live RAM
and
You have to be aware of how much stuff (apps, etc.) you have open, so as not to "push too far".

Having said that,
Since I started doing this, YEARS ago now, I haven't had any memory-related crashes.
It works for me.

I have 18 GB RAM. It is not Swap usage because it shows it as 0 in Activity Monitor.

 

[thebart]

I don't know the answer, but from my experience Mac OS writes to disk much more than Windows, for whatever reasons. My M1 mini has written about half as much to the system SSD in 9 months as my Windows machine did in 4 yrs. The Mac has 16gb RAM vs 12gb on the PC

 

[saudor]

I SOLVED the problem of "excessive disk writing", but "my way" is controversial in this forum.
I used terminal to DISABLE VM disk swapping, so the OS CAN'T do it.

For the average person, this isn't a good idea at all and should not be considered. You need to have seriously excess RAM for it to work. I did this for the lolz once and even with 32gb physical memory, the OS will hard crash around 25gb of actual usage and sometimes even much lower like 16. Some apps will become unstable without any swap.

Considering that macOS monterey+ can have random memory leaks, it's just not worth it for most people.

 

[Fishrrman]

saudor wrote:
"For the average person, this isn't a good idea at all and should not be considered. You need to have seriously excess RAM for it to work."

Case history:
My 2012 Mac Mini came with 4gb of RAM. I substituted 1 2gb DIMM with an 8gb DIMM, for a total of 10gb of installed RAM. It still runs fine with VM turned off.

My 2018 Mini came with 16gb of installed RAM. I turned off VM from the time I took it out of the box (Jan. 2019) and it's been running that way ever since. Doesn't crash, runs fine.

My 2021 MacBook Pro 14" came with 16gb RAM. I also disabled VM right from the beginning.
It, too, runs fine.

 

[saudor]

It, too, runs fine.

Yet it doesn't run fine for me on 32gb RAM. It's a serious YMMV that depends on workloads. SSDs have so much write endurance that no one needs to be doing this just to save writes. Swap also allows for more efficient use of physical memory. You are only misleading people and potentially screwing up their macOS experience if they fail to manually micromanage their RAM.

If you're that worried about writes, use firefox and turn off the disk cache and use only the RAM cache. I run my work firefox from a tiny encrypted SSD and daily writes went down from 10-20gb to just 1gb. Only did that for science/curiosity but there's not really any point in doing it.

 

[IG88]

I have 18 GB RAM. It is not Swap usage because it shows it as 0 in Activity Monitor.

In my case, and I suspect yours too, it doesn't show up as "swap."

I think one culprit is Safari caching video streams, like YouTube videos. I think the other culprit, at least for me, is Spotlight then insisting on constantly indexing the cache.

 

[Fishrrman]

IG88 observes:
"I think the other culprit, at least for me, is Spotlight then insisting on constantly indexing the cache."

In addition to my strategy above of disabling VM disk swapping, I also do this:
Since the very first time it was introduced, I immediately DISABLE Spotlight on all my Macs.
No drive "indexing" at all for me. Thank you very much.

If I need to search, I use either "EasyFind" or "Find Any File".

Not even a Spotlight icon left behind:

 

[ewitte]

Keep an eye on disk activity. I'm at 3TB with a 1 month old mac that averages 2h a day usage. Determined it was mostly OneDrive. Changed it to just sync my notes folder that is 22MB. I can pull the rest off of the NAS but I use an app running in wine (notepad++) not sure if it has network access. Tried several apps for Mac and haven't liked one the same yet. Ran in parallels for a bit but the 4GB usage was keeping me in the yellow (wine uses about 700MB).