Cache Hit Rate 0%

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ehjensen
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Cache Hit Rate 0%

Post by ehjensen »

I expect I may have misconfigured something.

I have a process that transforms multiple files in a pipeline - 80+ GB worth. Read a file, write the transformed file, read the transformed file, and write another transformed file, etc.

I use a 118GB Optane M2 for the cache and a 4TB RAID 1 HD for my data drive. My system has 128GB of RAM (Windows 11, i7-13700K). I have configured the cache as R/W shared.

I expected the L2Storage Read to increase once the initial files were all read and the recently transformed files started being processed. But that does not appear to be happening. (See attached screenshot). Could Windows 11 be caching all the written data in ram?

Any insight is appreciated.

Thanks,

eric

Screenshot 2023-04-01 135032.png
Screenshot 2023-04-01 135032.png (79.39 KiB) Viewed 496 times
janusz521
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Re: Cache Hit Rate 0%

Post by janusz521 »

I think it is up to the support team to provide the details, but it is quite likely that if you just read, transform and write a file, there is no need to read the same file more than once. All file content needed for transformation is probably mapped into the memory, so rereading it is unnecessary. Besides, Windows cache is quite good at caching at the file level, so there may be no work left for Primocache.
Nick7
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Re: Cache Hit Rate 0%

Post by Nick7 »

PrimoCache does not write to Level-2 cache immediately.
It does it when drives are idle.

What happens in your case - you read 80G file (cache still empty), you write new file (cache still empty), etc...
When there is no I/O activity, PrimoCache starts filling cache.. possibly even with data that does not exist there anymore.

This is feature I asked quite some time ago, but it's simply not there. (ability to fill Level-2 cache immediately, before data is expunged from Level-1, or simply immediately fill Level-2 if no Level-1 cache).
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Re: Cache Hit Rate 0%

Post by Support »

ehjensen wrote: Sat Apr 01, 2023 5:51 pm I expected the L2Storage Read to increase once the initial files were all read and the recently transformed files started being processed. But that does not appear to be happening. (See attached screenshot). Could Windows 11 be caching all the written data in ram?
I think in your case you need to turn on Defer-Write and set L2 cache 100% write. There will be no improvement on initial reading from the disk. When you write transformed files to disk, PrimoCache L2 can improve the writing. When you read the transformed files, because your RAM is large enough, Windows already cached your transformed files when you wrote them and Windows will not read them from disk.

Of course, the risk should be noticed when Defer-Write is enabled. For more information about Defer-Write, please see
https://www.romexsoftware.com/en-us/pri ... write.html
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Re: Cache Hit Rate 0%

Post by Support »

Nick7 wrote: Sun Apr 02, 2023 5:42 pm PrimoCache does not write to Level-2 cache immediately.
It does it when drives are idle.

What happens in your case - you read 80G file (cache still empty), you write new file (cache still empty), etc...
When there is no I/O activity, PrimoCache starts filling cache.. possibly even with data that does not exist there anymore.

This is feature I asked quite some time ago, but it's simply not there. (ability to fill Level-2 cache immediately, before data is expunged from Level-1, or simply immediately fill Level-2 if no Level-1 cache).
I don't think his problem is because of this. However, for the problem you mentioned, you can change the Gather Interval to INSTANT in the advanced L2 settings, which will fill the L2 cache almost instantly regardless of whether Windows is idle or not.
iskander
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Re: Cache Hit Rate 0%

Post by iskander »

Hi Eric, I ordered that exact same drive, can't wai to receive it, will be my first optane, is curious that there's almost no reviews or content about those drives anywhere, can you share some ramdom 4k 1qd threads screen captures please?

did you need to install intel rst windows app to recognize it or it was just like plugging any other ssd?

after formatting it do you lose too much space like other drives or do you get the full 118 gbs? I mean, that's already small as it is, but well, I'm planning on putting it in front of may system drive, a 980 pro

sorry for all the questions 🙏
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