L2 SSD Raid-0 Cache

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Jaga
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Re: L2 SSD Raid-0 Cache

Post by Jaga »

support wrote:
Thu Mar 05, 2020 5:02 pm
bkostas wrote:
Wed Mar 04, 2020 7:07 pm
I have another question. What do you think is a good investment for me.
1. 1x 1TB NVMe and replace 2x128GB SSD
2. 64GB RAM for L1 cache
or
3. New Raid controller and combine with 2x128GB SSD L2 Cache
Well, as I said before, larger cache size, better performance. If you have enough budget, I think the first priority is 1TB NVMe SSD, then 64GB RAM.
Totally agree for your scenario. The larger L1 is advantageous, but if you're using the L2 heavily, go with a larger/faster L2 first to help cover data better.
bkostas
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Re: L2 SSD Raid-0 Cache

Post by bkostas »

Nice, thank you. I already enjoy benefits in transfers from this software.
My current settings are:

1GB L1 Cache -> C:
10GB L1 Cache + 240GB Raid-0 L2 Cache (64k with 709MB overhead) -> D: (raid10)

Btw what is the ultimate setup for my setup?
2x 500GB NVMe Raid-0
and
64GB Ram

Or is it a waste?

Also can I use PrimoCache on an external drive connected through lan?
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Re: L2 SSD Raid-0 Cache

Post by Support »

You may check PrimoCache statistics, basically "Total Read", "Cached Read", "L2Storage Read", "Cache Hit Rate", "Free Cache (L1)" and "Free Cache (L2)". For the meaning of these terms, please see https://www.romexsoftware.com/en-us/pri ... mance.html
If free cache is larger than 32MB, and cache hit rate is high enough like 80% or more after running certain period, I think you may not need the new investment.
Please note that cache hit rate is related to your data access pattern. Cache Hit Rate = Cached Read / Total Read * 100%. If accessing hot data a lot, the hit rate will increase. If accessing new data which was not cached, hit rate will decrease.
bkostas wrote:
Fri Mar 06, 2020 9:35 am
can I use PrimoCache on an external drive connected through lan?
Sorry, but no.
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Jaga
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Re: L2 SSD Raid-0 Cache

Post by Jaga »

Support indicates no on network drives, but if you mount a network drive as a local iSCSI drive it should use block-level access, and -might- show up as cacheable by Primocache. I haven't personally tried it, but if you have a spare drive you can make available via iSCSI, it's worth a try.
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Re: L2 SSD Raid-0 Cache

Post by Support »

Sorry for my inaccurate answer. Jaga is right. Mapped network drives are not supported, but iSCSI drives are supported as they are mounted as local drives. For more information, please see https://www.romexsoftware.com/en-us/pri ... ation.html.
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bkostas
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Re: L2 SSD Raid-0 Cache

Post by bkostas »

support wrote:
Sat Mar 07, 2020 3:22 am
You may check PrimoCache statistics, basically "Total Read", "Cached Read", "L2Storage Read", "Cache Hit Rate", "Free Cache (L1)" and "Free Cache (L2)". For the meaning of these terms, please see https://www.romexsoftware.com/en-us/pri ... mance.html
If free cache is larger than 32MB, and cache hit rate is high enough like 80% or more after running certain period, I think you may not need the new investment.
Please note that cache hit rate is related to your data access pattern. Cache Hit Rate = Cached Read / Total Read * 100%. If accessing hot data a lot, the hit rate will increase. If accessing new data which was not cached, hit rate will decrease.
bkostas wrote:
Fri Mar 06, 2020 9:35 am
can I use PrimoCache on an external drive connected through lan?
Sorry, but no.
After 4 days of use:
1GB L1 Cache -> C:
Free L1 Cache R: 378MB
HitRate: 59%

10GB L1 Cache + 240GB SSD Raid-0 -> D:
Free L1 Cache R: 32.00MB
Free L2 Cache R: 32.06MB
HitRate: 76%

What do you think?
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Re: L2 SSD Raid-0 Cache

Post by Support »

Seems that your L2 cache is full for the D drive. If you have budget, it is worth increasing L2 cache size.
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bkostas
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Re: L2 SSD Raid-0 Cache

Post by bkostas »

Do you think 1GB L1 Cache -> C: is useless in my case?

L2 Cache on D: is now 110MB
Does that mean that I am still ok?
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Re: L2 SSD Raid-0 Cache

Post by Support »

I see C drive has 59% hit rate by using only 1GB L1. This is quite good. So I think you may keep this 1GB L1 Cache for C:
L2 cache hit rate is about 75%+. This is also good. But if you want to get it better, you may increase L2 cache size. Usually we see 90%+ hit rate indicating a good cache coverage.
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