primo cache writing more data at once than the L2 cache size is

FAQ, getting help, user experience about PrimoCache
Post Reply
npelov
Level 5
Level 5
Posts: 55
Joined: Thu Jun 30, 2016 3:01 pm

primo cache writing more data at once than the L2 cache size is

Post by npelov »

Hi,

I have 16GB L2 cache for my HDD. I was copying files and I forgot to turn off cache. I saw that L2 storage write is at about 1 GB when I turned off the cache. The total read was about 28GB. So I turn off the cache, but then the cache starts flushing. At the end 25 GB was written to L2. Why would you write 24 GB to a 16GB L2 cache partition? I think every now and again you should be checking if amount of cache that has to be flushed to L2 is bigger then the whole partition. Then discard the first data (first 8GB in my case) and flush the rest. It's a waste to wear down the SSD for no good reason. Also loading the system with copying data that will be erased later.

Please implement this! Thanks!

P.S. To replicate create a small cache partition - let's say 1 GB. Set the gather interval to a slow one (I used default). Then read (copy) a bit chunk of data - 10GB. Look at how much data will be written to the cache partition after the read has already finished.
Nick7
Level 5
Level 5
Posts: 46
Joined: Sun Jun 25, 2017 7:50 am

Re: primo cache writing more data at once than the L2 cache size is

Post by Nick7 »

PrimoCache will read everything it was read, and write (and re-write) data in L2 cache.
It's far from ideal... maybe one day it will be fixed.
User avatar
Support
Support Team
Support Team
Posts: 3623
Joined: Sun Dec 21, 2008 2:42 am

Re: primo cache writing more data at once than the L2 cache size is

Post by Support »

We have noticed this problem before, but solving this problem is not as simple as imagined. We will further improve it later.
Nick7
Level 5
Level 5
Posts: 46
Joined: Sun Jun 25, 2017 7:50 am

Re: primo cache writing more data at once than the L2 cache size is

Post by Nick7 »

'Simple' solution: Verify amount of data to be fetched into L2 is not bigger than L2 size. If it is, discard oldest data to be read, and append new data to be read at end of queue.
Even verifying this (size of queue to be read) every few seconds is good enough.
User avatar
Support
Support Team
Support Team
Posts: 3623
Joined: Sun Dec 21, 2008 2:42 am

Re: primo cache writing more data at once than the L2 cache size is

Post by Support »

It's not that simple... PrimoCache populates L2 data asynchronously. And when the cache space is full, it is also necessary to replace the old cache data with new data according to a certain cache replacement algorithm. These two factors complicate matters.
Post Reply