Romex Software Forum

Hello, I'm new to PrimoCache and I'm trying to get the most performance out of two somewhat older laptops.
The first laptop has 16 GB of RAM and a 8th gen Intel and 1 TB SSD, and the second has 64 GB of RAM and a 10th gen intel mobile Xeon a 2 TB SSD.
Both are running Windows 11 Pro and have write caching enabled for the SSDs.
I have five questions that the documentation didn't quite address.

Question #1:
In the settings for the Configure Parameters for New Cache Task i can set "OS Managed Memory (MM)". Does this refer to the memory that:
1. The Windows OS uses for writeback caching on a device
2. The Windows OS uses for read/write caching in general
3. The PrimoCache block-level cache
4. Memory that programs use like regular memory

Question #2:
So if I set this "OS Managed Memory (MM)" to 4096 on the 16 GB laptop, is that using 4 GB for PrimoCache? Or is that using 12 GB for PrimoCache (and leaving 4 GB for use as regular memory)?

Question #3:
If regular RAM usage hovers around 8-12 GB. For a total of 16 GB, is it best to use a 4 GB for Primo Cache and 12 GB for regular memory or would 8 GB for Primo Cache and 8 GB for regular memory be okay?
Also for the 64 GB laptop, if regular RAM usage hovers around 20 GB would it be better to use 32 GB for PrimoCache and 32 GB for regular memory? Or better to use 24 GB for PrimoCache and 40 GB for regular memory?

How much "safety" RAM should be left in addition to the amount regularly used and not given to PrimoCache?

I searched this forum a bit on this topic but some of the information is from some years ago

Question #4:
Also I can make another topic for this but I'm wondering, since these are laptops with a built-in batteries and they're on power 99.9% of the time, and they have Dropbox setup to sync immediately when files change to the other laptop over LAN and to the Dropbox cloud, what are the pros and cons of setting defer write to a high value such as 60 seconds (1 minute) or 900 seconds (15 minutes)?

Question #5:
For the cache hit and miss, what are good and bad values? Is 15% a good amount?
What percentage is so low to mean that PrimoCache isn't needed on a system?
What are ideal percentages to see?
Is this the cache hit rate for the Windows read and write cache, Windows SSD device caching, or for PrimoCache or multiple of those?

Thanks for PrimoCache. Seems like a great product

Realism wrote: ↑Thu Aug 31, 2023 11:04 pm In the settings for the Configure Parameters for New Cache Task i can set "OS Managed Memory (MM)". Does this refer to the memory that:

Please see https://www.romexsoftware.com/en-us/pri ... on.html#L1
After you set L1 cache, this part of physical memory will occupied by PrimoCache.

Realism wrote: ↑Thu Aug 31, 2023 11:04 pm So if I set this "OS Managed Memory (MM)" to 4096 on the 16 GB laptop, is that using 4 GB for PrimoCache? Or is that using 12 GB for PrimoCache (and leaving 4 GB for use as regular memory)?

This means L1 cache size is 4GB. That is using 4GB for PrimoCache as L1 cache.

Realism wrote: ↑Thu Aug 31, 2023 11:04 pm If regular RAM usage hovers around 8-12 GB. For a total of 16 GB, is it best to use a 4 GB for Primo Cache and 12 GB for regular memory or would 8 GB for Primo Cache and 8 GB for regular memory be okay?

I think you may reduce L1 cache size to 2~3GB. It is better to leave at least 1GB RAM free after deducting regular RAM usage and L1 cache size.
For more information, please see https://kb.romexsoftware.com/en-us/2-pr ... he-size-be

Realism wrote: ↑Thu Aug 31, 2023 11:04 pm Also I can make another topic for this but I'm wondering, since these are laptops with a built-in batteries and they're on power 99.9% of the time, and they have Dropbox setup to sync immediately when files change to the other laptop over LAN and to the Dropbox cloud, what are the pros and cons of setting defer write to a high value such as 60 seconds (1 minute) or 900 seconds (15 minutes)?

Please see https://www.romexsoftware.com/en-us/pri ... write.html
For high Defer-write latency, the pro is that you can reduce more writes on drives. The cons are 1) a high risk of data loss on unexpected shutdowns ( such as power loss and system crashes/freezes), and 2) the cache is too small to hold all deferred write-data, triggering "Urgent Writes" which bring poor write performance.
Usually the value of 60s is fine, 900s is a bit high.

Realism wrote: ↑Thu Aug 31, 2023 11:04 pm For the cache hit and miss, what are good and bad values? Is 15% a good amount?
What percentage is so low to mean that PrimoCache isn't needed on a system?
What are ideal percentages to see?

Please see https://kb.romexsoftware.com/en-us/2-pr ... e-hit-rate

Realism wrote: ↑Thu Aug 31, 2023 11:04 pm Is this the cache hit rate for the Windows read and write cache, Windows SSD device caching, or for PrimoCache or multiple of those?

Only for PrimoCache

Thank you very much for the great info. I didn't get an email to see this so I'm just seeing this now. Just have a few clarifications and about the cache hit rate percentages of how to know what number of percentage is good

1.
For the 64 GB laptop, to confirm, even with the unusually large amount of RAM, it's best to use total RAM subtracting normal RAM usage plus 1 GB.
So for 64 GB total and 20 GB regular use, and 1 GB extra, 43 GB for PrimoCache?

2.
For deferred writes on a laptop that is plugged in with a healthy battery and Dropbox syncing constantly, what is some good guidance for finding a good Defer-write latency? Just monitoring the 'urgent writes'? How many 'urgent writes' are generally viewed as okay? Zero? Or is there a better way to find a good latency?
If 900s is high maybe 300s would be good to start?

3.
About the cache hit rate specific values for the cache hit rate percentage, that article says how it works and how to improve it, but as a new user, what are good and bad values? Is 15% a good amount?
What percentage is so low to mean that PrimoCache isn't needed on a system?
What are ideal percentages to see?

4.
Also I notice when you set up a L1 cache that PrimoCache puts in a value. Does it do this just based on the total RAM or something else?

Realism wrote: ↑Tue Sep 05, 2023 12:49 am For the 64 GB laptop, to confirm, even with the unusually large amount of RAM, it's best to use total RAM subtracting normal RAM usage plus 1 GB.
So for 64 GB total and 20 GB regular use, and 1 GB extra, 43 GB for PrimoCache?

You can reserve more RAM for your system in case you need it. So if your regular usage is 20GB, you can set PrimoCache L1 cache to 40GB or less, leaving 4GB free for emergencies.

Realism wrote: ↑Tue Sep 05, 2023 12:49 am For deferred writes on a laptop that is plugged in with a healthy battery and Dropbox syncing constantly, what is some good guidance for finding a good Defer-write latency? Just monitoring the 'urgent writes'? How many 'urgent writes' are generally viewed as okay? Zero? Or is there a better way to find a good latency?
If 900s is high maybe 300s would be good to start?

Yes, monitor the "Urgent Writes" to make this value as low as possible. 0 is better. For your case, if you ensure your system is stable, you can start with the value of 300s.

Realism wrote: ↑Tue Sep 05, 2023 12:49 am About the cache hit rate specific values for the cache hit rate percentage, that article says how it works and how to improve it, but as a new user, what are good and bad values? Is 15% a good amount?
What percentage is so low to mean that PrimoCache isn't needed on a system?
What are ideal percentages to see?

The cache hit rate is related to data access. Usually for the Windows system partition, the cache hit rate (no L2 cache) can reach about 50% or higher. If after a few days of running, your hit rate is consistently below 5%, it means that the read cache is not effective.

Realism wrote: ↑Tue Sep 05, 2023 12:50 am Also I notice when you set up a L1 cache that PrimoCache puts in a value. Does it do this just based on the total RAM or something else?

The default value set by the program is based on the current available/free RAM.