RollingCache revisited, essential with aggressive culling, or set "Terrain Pre-Caching" to Ultra

Ok. I just check my c drive (OS) is an SSD and my other drives are HDD. Though cant tell whether redownload for my case is faster or SSD… maybe will try it out using both and compare which is faster…

Yes, just give it a go and see if there is an improvement either way

See the two videos I posted in the OP. That’s the difference between redownload (first video) and fetching it from Ram Disk. Rolling Cache on HDD/SSD will be in between those two scenarios.

Redownload is never faster.

Internet speed is up to 150mbps depending on your connection yet heavily depends on your physcial distance to server, congestion (prime time slow down), ISP capping your bandwidth or the server capping the upload. Plus downloading has the highest latency as in the slowest response.

HDD read speed is between 640 mbps and 1280 mbps with around 9ms response time (seek time) It’s actually possible to have lower internet latency yet consistency is lacking when it comes to internet traffic.

SSD read speed is up to 20,000 mbps (2.5 GB/s NVME speed) with avg 0.12 m/s response time, however write speeds are much slower, and it depends on how the file is accessed. Lot’s of little reads across the file are much slower.

Here’s the difference between HDD and SSD on my system


Reading the whole file in one go in the most optimal way gives you the full speed of SSD, However the rolling cache is accessed by tile (squares updating around you), little reads all over the place at best you get the 6,500 mbps figure (788.5 MB/s)

RAM transfer is between 50,000 mbps and 140,000 mbps with avg access time of 0.0000014 ms. The only thing slowing it down is if windows pages out the memory to its pagefile. Hence I advise a small ramdisk and rolling cache file to have it stay in memory and avoid using the pagefile. (Which should be on SSD, so you at least still have the benefits of SSD speed)

@gordongreig I also suspect that the Azure text to speech regularly switching back to offline voices is due to it getting bombarded with 'please expedite your climb/descent" all day long. SU5 brought a ton more unnecessary traffic on top of a lot more players.

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If MSFS downloads at 50 Mbit in average and you fly 4 hours per day it’s roughly 8 Mbyte * 4 * 3600 = 115,000 Mbyte ( or 115 Gbyte) per day. In 9 days it writes 1 Tbyte to the SSD. That’s 3 Tbyte per month and 36 Tbyte per year.

Let’s assume you have a 1 TB SSD with a TBW of 360 (this means that at least 360 TBytes can be written to the drive) it is supposed to last 11 years minimum. Of course it may last much longer.

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So quite a long time then! I doubt I’m doing anything like 115Gb a day on downloads through MSFS.

Depends which aircraft, which altitude and where you fly.

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This shows MSFS downloading data at ORBX LOWI.

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Now redo that while flying low over London, see what you get :wink: (if your ISP can keep up)

@gordongreig Having the pagefile on SSD is far more demanding if you’re limited on physical RAM. My poor SSD got hammered before I upgraded to 32GB RAM (long before SU5). Read and Write to the pagefile was constant while flying over PG areas with the sim allocating upwards of 22GB of ram. Yet you definitely don’t want a pagefile on a mechanical drive anymore. Best to make sure you’re not using more ram than you have to keep pagefile use to a minimum.

Of course if you’re not as crazy as me doing a 2600 hour world tour, your SSD will be fine!

I got ~ 200 Mbit/s peak when looking around and ~ 10 Mbit/s continous in cockpit looking straight out.

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I did manage a 350 hour RTW trip, but point taken. I have 64Gb RAM, so trying your ramdisk solution with 7.5Gb at the moment and experimenting with VR (just got a Reverb G2 headset - I’m stunned with how good it is!)

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Putting the cache on a RAM disk though means it’s never actually cached for anything other than the current session. If you fly commonly in the same area, you’re always downloading it fresh next time.

You can store the image file if you want. I play on a laptop and as long as I don’t reboot it’s always there. However since I always fly somewhere different, keeping it would be pointless anyway (Hence I’m only using 4GB for looking around and the occasional doubling back / looping around on approach)

Devs of Ram Disks have used their neurons.
You can save it on an image file, manually when you want, or automatically when you shut down the PC. Less then 20secs for a 20Go Ram Disk on an SSD.
And if it’s set, Ram Disk will automatically load this image at next startup.
Cannot determine loading time, too fast.

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It never fails to amaze me how people will represent something as a fact, when in reality, it is not.

SSD speeds are much higher nowadays especially with the M.2 NVMe gen 4.

And even external NVMe or SSD when connected to USB C gen 2 gets about 1000 - 1200 MB/s.

The amount of free RAM varies widely depending on add-ons.

I have 32GB RAM and when running MSFS vanilla with just a few add-ons leaves pretty much loads of free RAM after deducting the Windows Reserved.

But when I include one of the Live AI Traffic add-on it decreases dramatically and during the flight goes to zero and onto the page file.

So the RAM is very much depending on the load of the add-on.

Just sharing my experience here for those planning on using RAM.

Ah nice, that’s getting close to the speed of slow (for today) RAM. Of course the access times for SSD are measured in milli seconds, while for ram it’s in nano seconds. It probably won’t make much of a visible difference in sim with so many other things going on.

As long as you have rolling cache on and on either SSD or in RAM it will be faster than re-downloading the scenery again when turning the camera. Fast internet can beat a slow mechanical drive nowadays, yet the mechanical drive is probably still more reliable than the internet. (Plus where does the server store all that data?)

Anyway looking at FS2020 in flight, it reads a few 100 bytes per sec here and there from disk and only uses 10 GB of RAM. That’s it. While it’s talking to 8 different servers. Anything to lessen the burden on internet traffic helps, either disk or ram.

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Did you enable AWE in the advanced settings? If i’m correct it makes sure the reserved memory space will not be written to the page file.

Going to try with a 2GB space allocation.

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I have no idea what that is, but good tip!

I haven’t seen any page faults while flying (no pagefile use) but I’m using less than half my ram with the ram disk. (Pagefile still gets used for web browsing, fine)

It’s a memory API introduced in win7 (ish?), to get past the allocation of the 32 bit limits, as advantage it came with the fact it doesn’t get written to page files.

Is now fact “useless” these days on normal consumer pc’s, handy for databases etc… but anyway i digress. If RAM get’s consumed and the page file get’s more interesting. This could be an option to not go back to ‘disk’ performance :wink:

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