Romex Software Forum

So I just started looking into using PrimoCache to set up an SSD cache (primarily for my slower HDD), and as far as I can tell I think PrimoCache is a good solution and I think I have it mostly figured out, but assuming I have it mostly figured out I'm still looking for some advice on how much space I should allocate for the L2 cache volume that I (think I) want.

For some background on my setup it's a personal gaming computer with 3 drives. The 1st drive is a 46 GB SSD with the OS (Windows 7 Pro 64-bit SP1) and some other programs installed without much space left for anything else really, the 2nd drive is the 465 GB HDD (for mass media mostly) which is (as of recently) even more packed full than the 1st drive, and the 3rd drive is an extra 55 GB SSD (which is, also as of recently, mostly empty) that is primarily meant for installing games onto, so I have flexibility in managing the volumes on the 3rd drive which is the one I'd want to set up as an SSD cache.

The primary motivation for using PrimoCache in this case is that up until recently I had a large game installed on the 3rd drive (World of Warcraft), but with a recent patch update for the game its install size grew considerably larger, and now it can't even fit on the 3rd drive even if nothing else is installed on the drive. This means I've since had to move the game to my HDD where it loads much slower, so I've been looking into ways to either reduce the install size (which is a no go) or speed up the loading times a bit. I'm aware that I could just simply buy another somewhat cheap SSD and make a spanned volume with both, but I'd prefer to avoid spending more money (or at least, spend as little as possible) for now, and I'm also curious how much PrimoCache would help me now in this situation as well as maybe other hypothetical situations in the future.

So, considering that, the main question I have (for now anyways) is how much space (on the 55 GB SSD) would be recommended to allocate to the L2 cache volume? I was thinking of allocating at most 50 GB space to the L2 cache volume and the rest to a standard NTFS volume, but I was wondering if it would work just as well for me to allocate less space to the L2 cache volume or if it's strictly a case of more space is always better for the L2 cache volume? Since the L2 cache volume would be specially formatted that means I can't use that space to install some other small games (or whatever else) using that space, so if I don't need to allocate as much space to it then that could be helpful.

It wouldn't (shouldn't, anyways) really be a very big deal for me to just try it and see how it works because it would tend to not be a big deal to reformat and re-partition the 3rd drive (as needed) if I configure it poorly, but it would also still be somewhat annoying to do that so I'd prefer to be more informed and get it right the 1st time if possible.

Any other pertinent advice would be welcome too, such as whether or not there would be some weird issues that might come up with what I'm trying to do or if it's even actually worth doing this (considering my primary motivation) or whatever else.

If it were my setup, and I knew just how large the games (and used space on your HDD volume were), I'd allocate 50GB to the L2, and leave the remaining 5GB unallocated (in SSD terms - unprovisioned). Most SSDs see that unprovisioned space and utilize it well to extend the lifespan of the SSD. It doesn't have to be much - even 5% of the SSD total space (so 2.5GB minimum unallocated on yours).

When the L2's allocated space fills up and starts unloading old cache for new cache, you'll get re-writes (and slowdown) on the SSD which counts towards lowering the lifespan. Keeping that to a minimum by making the L2 cache volume as large as possible helps.

Just my .02, ultimately it'll be up to you. You can try a smaller L2 and monitor it for how much space fills up and stays full, and then monitor how many writes (in GB) per day it makes. If it writes a lot, chances are good it's not a large enough L2.

Jaga wrote:If it were my setup, and I knew just how large the games (and used space on your HDD volume were), I'd allocate 50GB to the L2, and leave the remaining 5GB unallocated (in SSD terms - unprovisioned). Most SSDs see that unprovisioned space and utilize it well to extend the lifespan of the SSD. It doesn't have to be much - even 5% of the SSD total space (so 2.5GB minimum unallocated on yours).

When the L2's allocated space fills up and starts unloading old cache for new cache, you'll get re-writes (and slowdown) on the SSD which counts towards lowering the lifespan. Keeping that to a minimum by making the L2 cache volume as large as possible helps.

Just my .02, ultimately it'll be up to you. You can try a smaller L2 and monitor it for how much space fills up and stays full, and then monitor how many writes (in GB) per day it makes. If it writes a lot, chances are good it's not a large enough L2.

I believe that both my OCZ brand SSDs (Vertex2 is C drive and Agility2 is G drive) both reserve a small amount of unallocated space so that neither drive is ever literally completely full, which also explains why they don't exactly have a lot of storage, so assuming that's correct (which I'm pretty sure it is) then I shouldn't need to worry about leaving more unallocated space myself.

I might try a slightly smaller (maybe ~45 GB) L2 cache volume to make a bit more room for the NTFS volume and just see how it goes, so if I do that and the cache runs out of space more quickly then how many writes would be considered a lot?

Depends on the endurance rating of your drive, how long you expect/want it to last. Ideally I would want it to not replace more than 20% of the cache per day. If it's replacing >50% of the cache every day, then it's not nearly large enough (unless you have a lot of writes to the drive as well).

You'll just have to test the size you picked out and go from there. Keep an eye on daily write totals through the L2 cache to the HDD. Since it's not a system volume, and you normally wouldn't install/download directly to it every day, writes should be light.

You can also look at the Cached Reads statistic, to get a feel for your hitrate on the cache. If your cache (for example) was only 5GB in size, you'd get a really low hitrate on Cached Reads. If it's super large (like a 200GB L2 cache), you'd have extremely high Cached Reads, even for a smaller period of time. The longer you leave the computer on, the more accurate an idea you get of whether or not your cache is doing a good job (large enough), or a poor one (too small).