Currently the software will wait for an idle period before it starts writing to the L2 cache. When it decides to do so it must then re-read the contents that should be cached so it can write it to the L2.
This means a busy disk will almost never receive the benefit! In fact a busy disk will be slower due to primocache.
Currently my system has been up 25 minutes, it has read 14GB from the HDD. So far it has only written 11MB to the cache! Such a tiny percentage.
Why instead can it not write to the L2 instantly (which a gather interval of instant suggests but it is clearly not true). An instant write would mean we don't need to go and read the data again some time later, the cache will warm faster, benefit comes in instantly, and there is no slowdown from an additional read.
Write to L2 Cache immediately
Re: Write to L2 Cache immediately
PrimoCache populates L2 data asynchronously in order not to affect the reading speed. You can set the L2 gather interval to "INSTANT" which means that PrimoCache will ignore the system busy state and issue an L2 gather request to the HDD immediately on the read completion. However, if the HDD is very busy, the collection request may be queued very late by the HDD because the HDD may have a large number of read and write requests that need to be processed first. That's why you may see the L2 populating still be slow even the INSTANT value is set.
We may try new methods to improve this issue while keeping disk read speed unaffected.
We may try new methods to improve this issue while keeping disk read speed unaffected.