Looking for some guidance on configuring PrimoCache

FAQ, getting help, user experience about PrimoCache
LawrenceLee
Posts: 13
Joined: Sat Nov 02, 2019 1:50 am

Looking for some guidance on configuring PrimoCache

Post by LawrenceLee »

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 a 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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Last edited by LawrenceLee on Mon Nov 25, 2019 2:05 am, edited 1 time in total.

uBlast
Posts: 9
Joined: Fri Aug 31, 2018 1:15 pm

Re: Looking for some guidance on configuring PrimoCache

Post by uBlast »

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: 2667
Joined: Sun Dec 21, 2008 2:42 am

Re: Looking for some guidance on configuring PrimoCache

Post by support »

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: 13
Joined: Sat Nov 02, 2019 1:50 am

Re: Looking for some guidance on configuring PrimoCache

Post by LawrenceLee »

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.
Attachments
2019-11-07 22_58_40-PrimoCache 3.0.9 - Registered.png
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Jaga
Posts: 467
Joined: Sat Jan 25, 2014 1:11 am

Re: Looking for some guidance on configuring PrimoCache

Post by Jaga »

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).

LawrenceLee
Posts: 13
Joined: Sat Nov 02, 2019 1:50 am

Re: Looking for some guidance on configuring PrimoCache

Post by LawrenceLee »

Jaga,

Thanks for the suggestion. However I am puzzled by something you wrote. You mentioned that you have 40GB established as L1 cache. Are you saying that you're using 40GB of RAM??

As for my L2 cache I have established 256GB of SSD free space for my 4TB RAID1 hard drive array.

As mentioned my 32GB RAM only yields 16GB of free RAM space if I allocate 8GB for L1 cache.

I decided to combine the caching task because that is what support suggested. They said that the software was smart enough to manage the common requirements. Actually when I compared the read performance of my C drive SSD to that of my D drive 4TB RAID its performance is as good if not better. I do not use the deferred write option because of the risks, so look at simply the read performance numbers.

I will attach some screengrabs below. Comments?

Thanks!
Attachments
2019-11-16 22_13_41-PrimoCache.jpg
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Jaga
Posts: 467
Joined: Sat Jan 25, 2014 1:11 am

Re: Looking for some guidance on configuring PrimoCache

Post by Jaga »

LawrenceLee wrote:
Sun Nov 17, 2019 6:15 am
Jaga,

Thanks for the suggestion. However I am puzzled by something you wrote. You mentioned that you have 40GB established as L1 cache. Are you saying that you're using 40GB of RAM??

As for my L2 cache I have established 256GB of SSD free space for my 4TB RAID1 hard drive array.

As mentioned my 32GB RAM only yields 16GB of free RAM space if I allocate 8GB for L1 cache.

I decided to combine the caching task because that is what support suggested. They said that the software was smart enough to manage the common requirements. Actually when I compared the read performance of my C drive SSD to that of my D drive 4TB RAID its performance is as good if not better. I do not use the deferred write option because of the risks, so look at simply the read performance numbers.

I will attach some screengrabs below. Comments?

Thanks!
Combining the L1 and L2 in your case is probably just fine too. The L1 by itself would have been totally insufficient, so it's good you set up a L2 like you did. The larger space on the L2 is going to help significantly with overall speed on the RAID volume(s). And the L1 at 8GB is probably okay, since blocks on C: are going to be accessed more frequently than the RAID volumes are most of the time.

One other way to do it is to separate out your SSD into two volumes, one for a boot (C:) L2, and one for a separate RAID L2. Say, 64GB for the first, and the remainder (192GB) for the RAID L2. You then create two cache tasks - the first uses 8GB of RAM for the L1 and the 64GB L2 space to cache C:. The second cache task uses just the 192GB space for the RAID's L2. That dedicates your L1 exclusively to covering the drive you care most about: installed programs, reading/writing, and the OS. And it has a little extra space in the 64GB L2 assigned to it to help boost it further. The RAID by comparison is covered by it's own large L2, and you have the best of both worlds.

LawrenceLee
Posts: 13
Joined: Sat Nov 02, 2019 1:50 am

Re: Looking for some guidance on configuring PrimoCache

Post by LawrenceLee »

Jaga,

That's interesting. I thought about setting up a separate task for my boot drive. But since it's an SSD does the setting up L2 cache space provide any performance improvements, since I would be caching and SSD with an SSD. Since SSD's have fast random-access and the RAM L1 cache is designed to improve the performance of the SSD, is there really going to be any performance improvement with an SSD with SSD L2 cache. Seems redundant. ;)

I'm interested to know what you found. Could you post some numbers, pictures or examples to show that this L2 for Boot SSD improves matters? It would be nice to hear from support on this question too.

Regards,
LawrenceLee

LawrenceLee
Posts: 13
Joined: Sat Nov 02, 2019 1:50 am

Re: Looking for some guidance on configuring PrimoCache

Post by LawrenceLee »

Jaga, support,

This was interesting. The large 256 GB cash is really doing something.

I mapped two files; a 64 GB and a 100 GB that are resident on my 4 TB raid as a virtual disks (E: and F: drives). It appears that PrimoCache cashed possibly the entirety of these files as I accessed individual files out of these virtual disks.

The free space of my 256 L2 cache dropped to 32 GB. During that time my disk monitoring program Hard Disk Sentinel measured temperatures on my L2 SSD caching drive up to 51 Celsius. That's indicating that lots of activity was going on in the cache.

Wahoo! This program is really working hard!
Attachments
2019-11-23 22_45_01-Disk_ 1, CT500MX500SSD1 [1939E2210EFA]  -  Hard Disk Sentinel 5.50 PRO.png
2019-11-23 22_45_01-Disk_ 1, CT500MX500SSD1 [1939E2210EFA] - Hard Disk Sentinel 5.50 PRO.png (217.18 KiB) Viewed 2099 times
2019-11-23 22_46_02-PrimoCache 3.0.9 - Registered.png
2019-11-23 22_46_02-PrimoCache 3.0.9 - Registered.png (254.64 KiB) Viewed 2099 times

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Jaga
Posts: 467
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Re: Looking for some guidance on configuring PrimoCache

Post by Jaga »

LawrenceLee wrote:
Sun Nov 24, 2019 6:38 am
That's interesting. I thought about setting up a separate task for my boot drive. But since it's an SSD does the setting up L2 cache space provide any performance improvements, since I would be caching and SSD with an SSD. Since SSD's have fast random-access and the RAM L1 cache is designed to improve the performance of the SSD, is there really going to be any performance improvement with an SSD with SSD L2 cache. Seems redundant. ;)
Yes - I may have missed that part. If the C: drive is an SSD, placing a L2 on it is totally redundant and can actually hurt performance. Putting the entire L2 256GB on the RAID is the best option, which it looks like you did. Glad to hear the performance is turning out well for you now. :)

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