Looking for some guidance on configuring PrimoCache

FAQ, getting help, user experience about PrimoCache
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LawrenceLee
Posts: 5
Joined: Sat Nov 02, 2019 1:50 am

Looking for some guidance on configuring PrimoCache

Post by LawrenceLee » Sat Nov 02, 2019 3:10 am

All,

Just getting started using this excellent software. However I'm a bit puzzled as to how to configure it. Here's my system.

i7 3770K
32GB RAM
250GB SSD booting windows 10
500GB SSD with 110GB Windows 7 partition => 356GB free to use as an Cache Space
4TB RAID1 WD Red data drive system.

Here are my questions:

1. Should I set up a single task for my boot SSD and my RAID1 4TB hard disk?

2. How much space should I set up as L2 Cache Space for my 4TB RAID1 data drive system?

Currently I am using a single task with 4GB of RAM allocated as L1 cache, and 64GB of my SSD allocated as L2 cache. This configuration yields good performance and leaves me with 16GB of RAM free. Primocache is using a total of 9GB with included overhead with 4KB cluster size.

Monitoring my L2 cache usage over many boots, over many days the "Free Cache (L2)" parameter reports 56GB. I have to wonder if my 64GB of SSD space is really necessary then.

3. Does that mean that only about 8GB is being used by the program?

My motherboard natively can use Intel's rapid storage technology to accelerate my hard drive as well, with up to 64 GB of my free SSD space. It seems dangerous to me to use to catching programs simultaneously.

4. Could I use RST Caching and PrimoCache together safely?

What are your thoughts about how to this set up?
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uBlast
Posts: 6
Joined: Fri Aug 31, 2018 1:15 pm

Re: Looking for some guidance on configuring PrimoCache

Post by uBlast » Wed Nov 06, 2019 4:58 am

I have some questions about my setup as well. Posted already on these foruns asking for guidance but had no response. The support unfortunately lacks a little bit. Despite of that PrimoCache is still a nice piece of software.

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support
Posts: 2511
Joined: Sun Dec 21, 2008 2:42 am

Re: Looking for some guidance on configuring PrimoCache

Post by support » Wed Nov 06, 2019 4:13 pm

I'm sorry for the late reply because recently we are kind of busy. :(
LawrenceLee wrote:
Sat Nov 02, 2019 3:10 am
1. Should I set up a single task for my boot SSD and my RAID1 4TB hard disk?
It's up to your goal. Cache content in a cache task is independent of, that is not affected by, each other. This means that if you use separate cache tasks, drive access activities in a cache task will not affect the cache content or trigger cache replacement algorithm in other cache tasks. The shortage is that you have to assign cache space for each task and you may not have enough L1/L2 resource. If you use one cache task for all drives, you may assign a large cache space and let PrimoCache automatically schedule the cache space for each drive based on their access activities. The shortage is that when cache space is full, access activities in one drive may push out old cached data for another drive.
I think for simplicity you may just use a single cache task.
LawrenceLee wrote:
Sat Nov 02, 2019 3:10 am
2. How much space should I set up as L2 Cache Space for my 4TB RAID1 data drive system?

It depends on how much hot-data (frequently accessed) will be accessed from the HDD drive. Generally speaking, larger cache size, better performance. You may have known that when cache space is full of cached data, PrimoCache has to discard some old cached data to release space for caching new data. So if cache space is too small, PrimoCache might do the data replacement frequently, affecting the performance.
LawrenceLee wrote:
Sat Nov 02, 2019 3:10 am
3. Does that mean that only about 8GB is being used by the program?
Currently it is.
LawrenceLee wrote:
Sat Nov 02, 2019 3:10 am
4. Could I use RST Caching and PrimoCache together safely?
No need to run both.
LawrenceLee wrote:
Sat Nov 02, 2019 3:10 am
What are your thoughts about how to this set up?
In your setting, 4KB block size causes about 5GB memory overhead which is quite a waste. Small block size brings huge memory overhead. I think you may increase block size to reduce memory overhead and give these memory to level-1 cache.
Primo Ramdisk | PrimoCache
Romex Software Support

LawrenceLee
Posts: 5
Joined: Sat Nov 02, 2019 1:50 am

Re: Looking for some guidance on configuring PrimoCache

Post by LawrenceLee » Fri Nov 08, 2019 6:59 am

Support,

That was very helpful. Based on your recommendation I decided to go to a 16K block size and 8GB of memory for my L1 Cache. This arrangement leaves me with 16GB of free ram. Thanks again.
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Jaga
Posts: 419
Joined: Sat Jan 25, 2014 1:11 am

Re: Looking for some guidance on configuring PrimoCache

Post by Jaga » Fri Nov 08, 2019 10:10 pm

LawrenceLee wrote:
Fri Nov 08, 2019 6:59 am
Support,

That was very helpful. Based on your recommendation I decided to go to a 16K block size and 8GB of memory for my L1 Cache. This arrangement leaves me with 16GB of free ram. Thanks again.
Using a cache size of 8GB to cover -both- a boot drive, -and- a 4TB data drive means you are going to end up with a rather low cumulative hit rate over time. I for example, have a 40GB L1 cache task setup against just my C: (boot) drive, to ensure very high hit rates.

A rule of thumb I go with is to have as high a data coverage percentage as possible. i.e. if I'm caching a large data drive and only have ~8 GB of RAM to give it in a L1, I don't even bother. In that scenario, I'd go get a decently fast SSD and set it as the L2 for the data drive, leaving all of my allocated RAM to the boot drive's L1.

Assume for a moment that your RAID drive is populated with 2TB of information. Also assume that your 8GB L1 cache task is going to try and split between C: and the RAID, and the RAID is less frequently accessed, so it might only get ~2GB of the L1 cache. Divide that 2GB by 2000GB and you get ridiculously small coverage (about a tenth of a percent). You should try for 5% data coverage at a minimum, 10% is more ideal - meaning your 3TB of data needs at least 100 GB of cache, or ideally 200+ GB (a L2 SSD).

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