How to choice best device for caching. and others...

[einstein1969]

I'm seeing ... USB 3.0 is required (I have it), it's just too expensive.

I tried to see in my country and on amazon they only have one but it costs 324 € (377$) + 3.5 € transport

[Support]

As InquiringMind and Jaga suggested, replacing your disk with an SSD is your best option. The flash drives you used for level-2 cache are too slow. Only Sandisk Ultra Fit usb device meets the requirement just under the wire. If you still want to use pen drives, you may turn off the defer-write and see if the problem still happens.

[einstein1969]

As InquiringMind and Jaga suggested, replacing your disk with an SSD is your best option. The flash drives you used for level-2 cache are too slow. Only Sandisk Ultra Fit usb device meets the requirement just under the wire. If you still want to use pen drives, you may turn off the defer-write and see if the problem still happens.

thanks for the answer, I'm trying "primocache" with only L2 set for reading to simplify. I would like to know how I should choose a possible flash drive. In particular, what are the parameters to be taken into consideration. I'm curious how it reads "before cache" on the flash drive. I try to explain myself better. If I have a 4k block cache, how is the process involved?

[Support]

In particular, what are the parameters to be taken into consideration.

Speed and write-cycles, as well as capacity, should be considered. L2 native speed should be at least 2x faster than drives to be accelerated. Of course, faster, better.

[einstein1969]

I have tried to search for write-cycles for my flash drives but without success.

I did a test on all of them and I saw that the startup speed (from the bios logo to the desktop appearance) remains unchanged (1:18) which for me is a good speed. I also measured the boot time plus the loading of a game (asphalt9 for example). In this case the first cache reduces the total time from 3:26 (3 min and 26 sec) to 2:20 seconds. That is, the loading of the game goes from 2:26 to 1:02. The speed is more than double, wow !.



I did the test on all three flash drives. The result is the same. I set L1 = 0, L2 = 6144MB 100% Read, Gather = DEFAULT, and I tried the blocksize at 4KB, 16KB. The result is almost the same in all cases. I have questions. Tests with cristaldiskmark show different data for the three flash drives, but the speed test results are the same.
Why? How should I choose the speed? Blocksize does not seem to affect speed. It's normal?

The next question is about boot time. To simplify things I have disabled the sysmain service which takes care of the SuperFetch I believe. I have seen that after repeated booting the amount of data in the L2 cache is always lower than total read and the cache hit rate never exceeds about 60%. What did I do wrong?

[Support]

If L2 cache device is internally connected by sata, pci-e etc, it will be detected by Windows early at the boot phase. The boot cache hit rate usually can reach 90% or above. However, if L2 device is connected by usb, it is detected by Windows late during the boot. So the boot time might not be greatly improved.

Regarding the speed of these flash drives, crystaldiskmark shows the speed of 4KB (random) and 1MB (sequential). Some of your flash drives have better sequential access speed while some have better random speed. None of them is outstanding to others. In real-world scenarios, read-data block ranges from 512K to 2MB (or more), I think that's why you see close performance boost when using these flash drives of yours.

[einstein1969]

Thank you for your answers. I realize that my questions are very difficult.

I update you. I don't know how but I did other reboots and things suddenly changed at some point. From 55% it jumped to 85% of Hit.

I then changed the blocksize. Now I am using 16KB blocks for the cache to keep the overhead down. Can you tell me what disadvantages/advantages there might be to using a larger blocksize?



Also I read on the forum that it is advisable to avoid defragmenting the disk (HDD in my case). Can you explain to me why?

[Support]

In your case, I think 4KB block size (which equals to the file system cluster size) might reach the best performance, especially on sequential read/write performance. Bigger block size will reduce memory overhead and CPU utilization.

Also I read on the forum that it is advisable to avoid defragmenting the disk (HDD in my case). Can you explain to me why?

No, officially we didn't advised that. It's up to users to enable/or disable defragment.
Defragment will invalidate (remove) some L2 cache data because data are moved from the source disk. That's why some users advise to avoid defragment.

[einstein1969]

Thanks, I'm using the 4KB block and have set up a 4GB cache to get started.

There is a problem. I've done a few reboots but the cache hit ratio remains at around 60%. Before it was like unlocked and it had reached about 85%, now it seems fixed at 60%.

How can I solve?

[Support]

After you boot up, leave Windows idle for a while. PrimoCache will populate data into L2 cache when system is idle. You may check the statistics "L2Storage Write" which refers to the L2 populating.

PS. cache hit rate depends on the data access pattern. For usb L2 cache, 50%~80% is normal for the boot process.