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How is write cache implemented

Posted: Thu Jun 30, 2016 3:07 pm
by 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?

Re: How is write cache implemented

Posted: Sat Jul 02, 2016 3:31 pm
by Support
npelov wrote: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.
npelov wrote: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. :)
npelov wrote: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.

Re: How is write cache implemented

Posted: Sun Jul 03, 2016 4:35 pm
by 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.

Re: How is write cache implemented

Posted: Mon Jul 04, 2016 12:23 pm
by Support
Yes, L2 cache is not used for write cache.

Re: How is write cache implemented

Posted: Wed Jul 13, 2016 11:00 pm
by 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!

Re: How is write cache implemented

Posted: Thu Jul 14, 2016 10:49 am
by npelov
I agree, but there should be an option to turn it on or off in configuration. SSDs won't like it much