Upgrade Choices

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Feb 22, 2017
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I have a TrueNAS box (see signature) that I'm thinking of upgrading due to tax time and refund (yay!).

The choices are going from 128GB of RAM to 512GB of RAM or go from 10 2TB (8TB-ish of usable space) Red Pros to 10 6 TB (guesstimating around 24TB-ish of usable space) Red Plus drives (I may go with 12 of them, depends on how I feel). The main issue is that I know if I go with the expanded space, the memory should probably be expanded as well. I'm just not completely sure of the "rule of thumb" calculation for pool size vs memory.

The 6TB drives are also 5400RPM vs the 2TB 7200RPM (they're both CMR, though).

It's getting slightly over that 50% very loose general rule of thumb for usage, so I'm curious what's going to be the best "bang for the buck", so to say so that I don't lose the very nice speeds and stability I have going on currently.

TIA
 

artlessknave

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Oct 29, 2016
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128GB of RAM is more than sufficient. if you were at 32gb or 64 that might be different but 128 is a very good number for the size of storage you are stating.
note that unless you are doing sync writes the SLOG is pointless. and even then, for home users its usually pointless or can slow your pool down.
a sync write with SLOG will almost always be slower than an async write.
 

Ericloewe

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The choices are going from 128GB of RAM to 512GB of RAM
What on Earth for?
10 6 TB (guesstimating around 24TB-ish of usable space)
More like 21 TB, less if you want to stay closer to 50% for small block performance reasons.
The main issue is that I know if I go with the expanded space, the memory should probably be expanded as well. I'm just not completely sure of the "rule of thumb" calculation for pool size vs memory.
Even for the most pessimistic interpretation of the rule of thumb, 128 GB would be good for some 128 TB of raw storage. And again, it's just a rule of thumb.
 
Joined
Feb 22, 2017
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What on Earth for?

More like 21 TB, less if you want to stay closer to 50% for small block performance reasons.

Even for the most pessimistic interpretation of the rule of thumb, 128 GB would be good for some 128 TB of raw storage. And again, it's just a rule of thumb.
Welp, that answers that. :grin: Thanks!

Long story short, the general view seems to be "throw RAM at block storage", but there's always "rules of thumb". I couldn't remember the numbers and the storage nerd I bounced things off of 8 years ago when I stood up my FreeNAS iSCSI box isn't available anymore to reign in my tendency of "morer is betterer" for some things (like RAM for almost anything, usually).

Well then. . .HDDs it is. Staying below 50%, I'll have approximately 10-12TB of "usable" space with 24-ish TB of "actual" space. Reading Greco's guide, 5400 RPM really shouldn't be an issue, either.
 

artlessknave

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more RAM is always better, but in your case, with the given "more storage OR more RAM" more storage is a better choice, particularly because you wouldn't just be adding more sicks, you would be replacing all the RAM, and, additionally to that, that board would require 3DS LRDIMM to get to 512GB, and that would likely be cripplingly expensive. a single 128GB 3dsLRDIMM could be the price of your 10 6tb drives....
would likely be better off replatforming your system entirely if the goal was more more RAM.
 
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