How is write cache implemented

[npelov]

Hi,

With OS cache (in both windows and linux ) I usually have the problem that computer gets slow after big files copying, because all the cache is replaced with the file that's being copied. So I have few questions:
1. Is this going to happen in PrimoCache? Will big writing remove frequently used read cache?
2. How do you decide what part of the memory to leave for write cache and what for read.
3. will write cache write the sectors in order so the head travels in one direction only?

[Support]

1. Is this going to happen in PrimoCache? Will big writing remove frequently used read cache?

Yes. But you may choose "read-only" cache strategy to disable caching write-data.

2. How do you decide what part of the memory to leave for write cache and what for read.

Sorry, all cache space can be used for both read and write cache. However, we may support separated read and write cache space in future.

3. will write cache write the sectors in order so the head travels in one direction only?

Yes. PrimoCache always tries to write sectors in order if possible.

[npelov]

2. That's unfortunate. If you do implement something in the future, please put a limit how much (maybe in %) of the whole L1 cache can be used for write buffers. That would keep the most used read cache.

I guess in my case it doesn't matter that much because I have fast SSD L2 cache and I read that L2 is not used for write cache.

[Support]

Yes, L2 cache is not used for write cache.

[kalua]

I would dearly love for write cache to use L2. I have a 512GB Samsung 950 NVMe drive that has awsome write speed. If that could be used as the write cache for my 6TB Seagate spinning disks, that would be the perfect solution for my big file saves and database sorting.

Please make it happen!

[npelov]

I agree, but there should be an option to turn it on or off in configuration. SSDs won't like it much