Romex Software Forum

Hello Folks,

I've been evaluating PrimoCache for a week now and its been working great, definitely a new killer app for me. I would like to see if I could get some tips or recommendations on my current configuration from the community.

Goal: Accelerate both reads and writes mainly for my raid volume. I use this PC mainly for digital audio workstation tasks so I frequently load up multi-gigabyte sample libraries stored on the raid volume. Accelerating those reads is probably my top priority. I also have this volume shared with my home network servers through cifs for misc storage and bulk downloads however, this is pretty light.

Both my OS ssd and disks in raid are aging so I would like to be avoiding both reads and writes to them as much as possible. Also, for the same reason, I want to have my disks in raid spin-down/sleep to be as power conscientious as possible. I had some great results after converting my 16g intel optane module to be used as L2 cache with primocache, so much so that I purchased a generic 128g nvme ssd to replace it.


Below is my current setup:

Hardware:
-32g RAM
-128g m.2 nvme ssd (cheap, wouldn't trust it as my OS drive)
-500g SATA3 SSD - OS drive
-4x 3TB 3.5 spinners in hardware raid 5 - formated as 1 ntfs volume and contains my music libraries and plugins

PrimoCache config:
-8g L1 cache - no write/read separation
-119g L2 cache - again no write/read separtion - how would setting 50%/50% differ?
-gather interval "1"
-block size 128KB (this is what my raid5 stripe size was deployed with)
-enable defer-write - latency 300
-write mode average - flush L1 to L2
-prefetch last cache - start at boot
I'm thinking about making a separate smaller cache task for my OS disk and then providing 75% of my L1/L2 to my raid... Still unsure. Looking for any suggestions!

Thanks,

-Neil

Would also like to mention that my audio software is setup to be ultra low latency and try to keep everything in ram and limit reads to slow storage as it causes latency and ultimately audio drop outs.

neilmacneil wrote: ↑Fri Mar 12, 2021 8:29 pm-4x 3TB 3.5 spinners in hardware raid 5 - formated as 1 ntfs volume and contains my music libraries and plugins

This is going to be a problem to cache with any decent amount of hitrate, given the total volume size of 9 TB in RAID 5. To do the job you're going to need at minimum, a 1TB fast SSD or NVMe. Ideally you'd get two 1TB drives and RAID 0 them in hardware to cover against filling the array up in the future.

Assuming the volume is ~50% full and your L2 is only 1TB, it gives you data coverage of 1 TB/4.5 TB = 22% possible cached data (20% is ideal in my opinion). That's not even considering caching your OS drive, or keeping space in the L2 free for dedicated deferred write space.

The last time I rebuilt my server storage in Stablebit Drivepool (9x 8TB spinners, 2x parity stored on 4x other drives), I realized that Primocache's limitations on L2 size wouldn't even begin to touch my data there, even if it was 1/4 full. I simply made sure it had a good gigabit connection on the network, and installed Primocache running against the OS drive. The data on the storage array isn't cached at all - it just wasn't feasible.

So while your idea has the possibility of succeeding due to the size of your target volume, you couldn't possibly pull it off with a 128GB SSD. The result even with your data volume only 25% full is: 128 / 2250 = 5.7% data coverage (far too low in my opinion). And again, no dedicated write space in the L2 means it'll constantly be shoving data out of the L2 to try and make space for writes, larger ones will hurt hitrate even more.

See if you have room in the budget to pick up a 1TB fast SSD, or decently fast NVMe. Or two 512GB in RAID 0. In the future when your data drive fills, you can expand (if you have RAID connector capacity) to 2x 1TB drives for a larger L2 volume.

Thanks, definitely cleared a good amount up for me!