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Valantar

Shrink Ray Wielder
Jan 20, 2018
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Interesting, I thought Optane was only used as a cache option for HDDs.
Also surprised to hear that nvme is not the top notch solution for such a use case!
Thanks for the info!
Those cache drives are the low capacity consumer Optane products (which topped out at 120GB I think?). That drive is an enterprise/workstation drive with higher capacity (and a price to match). Optane is much faster than NAND, especially for random workloads and low queue depths, but it scales poorly in terms of density so it's poorly suited for mass storage sadly.
 
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tasen

Caliper Novice
Apr 30, 2020
23
43
Interesting, I thought Optane was only used as a cache option for HDDs.
Also surprised to hear that nvme is not the top notch solution for such a use case!
Thanks for the info!
I had to learn that the word "cache" drive doesn't exist in the truenas world and especially truenas forum 😅 But yeah, it's much easier to call it cache drive then try to explain what it ectually does 🙂
Funny thing is ixsystems (developer of truenas) also use the therm "write cache" in their description for their own systems ...
 

Valantar

Shrink Ray Wielder
Jan 20, 2018
2,075
2,057
I had to learn that the word "cache" drive doesn't exist in the truenas world and especially truenas forum 😅 But yeah, it's much easier to call it cache drive then try to explain what it ectually does 🙂
Funny thing is ixsystems (developer of truenas) also use the therm "write cache" in their description for their own systems ...
Are you using it as an L2ARC? I was planning to use a spare 500GB SSD as a "cache" before I started learning the ins and outs of TrueNAS, and ended up skipping L2ARC entirely - it just didn't seem useful for my use case.
 

tasen

Caliper Novice
Apr 30, 2020
23
43
Are you using it as an L2ARC? I was planning to use a spare 500GB SSD as a "cache" before I started learning the ins and outs of TrueNAS, and ended up skipping L2ARC entirely - it just didn't seem useful for my use case.
No not using as L2ARC. Only for SLOG/ZIL ("write cache" 😁 ).
Yeah, adding more RAM instead of adding a SSD for L2ARC seams the better solutions. Adding a L2ARC device wil rob ARC (RAM) space to map the L2ARC which could also cost you performance than giving you a performance boost 😲

Did you try Truenas Scale already? Overall it's more compatible to my system and better performing than Truenas Core (13.x) but that's because of my old Intel 10G Nic I think
 
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Valantar

Shrink Ray Wielder
Jan 20, 2018
2,075
2,057
No not using as L2ARC. Only for SLOG/ZIL ("write cache" 😁 ).
Yeah, adding more RAM instead of adding a SSD for L2ARC seams the better solutions. Adding a L2ARC device wil rob ARC (RAM) space to map the L2ARC which could also cost you performance than giving you a performance boost 😲
Ah, you have a use for that? I decided against that seeing how my NAS doesn't get that much write activity. Or, the media drive does, but that isn't anywhere near performance sensitive, and rather intermittent still.

I didn't know that about the performance impact of L2ARC btw - though it does make sense. If the L2ARC is "level 2, slower RAM", then it makes sense that some RAM capacity is lost to keep things coordinated.

Speaking of RAM, I actually recently saw someone running just 16GB of RAM for a 24GB ZFS pool (with no L2ARC), and apparently it performed well for them. That definitely surprised me. Still, I'm happy I got 32GB for the sake of future-proofing - I'll be replacing my two 4TB drives with 8TB ones as soon as I get the time, which will push my total capacity well past 16TB raw.
Did you try Truenas Scale already? Overall it's more compatible to my system and better performing than Truenas Core (13.x) but that's because of my old Intel 10G Nic I think
I'm running Core, haven't even updated the system much (still on 12.0 U6.1), prioritizing keeping it running and working well. It's at 200 days of uptime right now, so I'm pretty happy. Still, lots of changes coming this summer - that storage upgrade I mentioned, plus finally getting my 2.5G NIC wired up. It's installed and activated (it's a Realtek NIC, so it needs a couple of tunables to activate the driver), but I'm waiting on having the NAS taken out of its cubby for actually giving it an IP as that necessitates deactivating the built-in NIC, and knowing my luck something will no doubt go wrong with that handoff :p And having to get it out of there to install a GPU and get command line access to fix any issues will be ... well, not fun!
 

tasen

Caliper Novice
Apr 30, 2020
23
43
I tried to setup my Truenas as good as it's possible which means sync writes on my pool, a SLOG Device (for performance), ECC Memory, server hardware, etc. This is why I have the optane SSD.

Isn't 16GB the minimum for Truenas? Or was it 8GB?
32GB is OK, but the more you have, the better peformance gets. My goal is at least 64GB. Had this on my previous setup.

How do you replace them? Replace one 4TB with a 8TB, let the Raid rebuild and than replace the second one? Or do you go the backup and restore path?

Oh good luck than on your planed tasks and upgrades 😀
Network changes can be tricky but I never lost my access to the system, just had some weird situations by changing NICs 😩
 
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