FreeNas mini vs ram recommendation

[JibbaJabba]

Hi all

From what I understand with freenas is that 1tb of data = 1gb of ram....

But when browsing the freeNas 8bay mini....it doesn't seem to follow that rule?

https://www.ixsystems.com/freenas-mini/
32gb ram...with 8 x 6tb hdds.

What am I missing?

 

[BigDave]

From the web page you linked...
"The FreeNAS Mini XL offers enterprise-class hardware to home and small office users."
The 1GB of RAM for each 1TB storage of is more of an enterprize level guide line than a fast rule.
That along with compression as a default condition, means for most SOHO use cases the performance
is fine.
If you want/require more performance, you'll have to go with the more advanced products they offer.

 

[jgreco]

The 1GB of RAM for each 1TB storage of is more of an enterprize level guide line than a fast rule.

The hell it is. The thing here is that out at 32GB, there's a lot more squish in that guideline than there is down at 8 or 16GB, which is usually where people are asking about it.

But in this specific case, 8 x 6TB HDD's in RAIDZ2 would work out to 32GB of RAM for 36TB of disk, which is bang on for the 1GB:1TB rule. And if you use the "used pool space" variant of that rule, 36 * 80% = 28.8TB, so that's even better.

 

[JibbaJabba]

The default slider setting in raidz and it's an option...
Defaulting to 42tb....

 

[jgreco]

Perhaps, but no one in their right mind would do RAIDZ1 on 42TB.

... says the guy who's got 5 8TB drives striped. Haha.

 

[BigDave]

You might find this post useful.
https://forums.freenas.org/index.php?threads/zfs-raid-size-and-reliability-calculator.28191/
The 42TB you speak of is partitioned space. But there is also overhead, redundancy, swap space, etc.
to take into consideration here.

 

[Ericloewe]

Perhaps, but no one in their right mind would do RAIDZ1 on 42TB.

... says the guy who's got 5 8TB drives striped. Haha.

Over USB, too (pun very much intended), IIRC.

 

[jgreco]

Over USB, too (pun very much intended), IIRC.

No need to be so jealous, @Ericloewe ...

Code:

# zpool status usbfun
  pool: usbfun
 state: ONLINE
  scan: scrub in progress since Mon Apr 11 04:32:35 2016
  16.5G scanned out of 15.0T at 39.6M/s, 110h19m to go
  0 repaired, 0.11% done
config:

  NAME  STATE  READ WRITE CKSUM
  usbfun  ONLINE  0  0  0
  gptid/6a437453-fb41-11e5-9d4a-984be106bf17  ONLINE  0  0  0
  gptid/6bdfed5a-fb41-11e5-9d4a-984be106bf17  ONLINE  0  0  0
  gptid/6d7c510d-fb41-11e5-9d4a-984be106bf17  ONLINE  0  0  0
  gptid/6f330b74-fb41-11e5-9d4a-984be106bf17  ONLINE  0  0  0
  gptid/70f3d2d1-fb41-11e5-9d4a-984be106bf17  ONLINE  0  0  0

errors: No known data errors

Not everyone can have a ZFS array that scrubs at 40MB/sec!

 

[DrKK]

The hell it is. The thing here is that out at 32GB, there's a lot more squish in that guideline than there is down at 8 or 16GB, which is usually where people are asking about it.

Jgreco's hit it here. Once you start having 32GB or 64GB of RAM, the guideline is quite squishy, indeed. You could have 50TB with 32GB of RAM without ill effects, for example, in many cases. But you would almost never want 12TB with 8GB of RAM, which is a similar ratio. The thing is the scale.

As he says, the 1GB->1TB is more tightly followed down at the smaller sizes.

 

[jgreco]

But you would almost never want 12TB with 8GB of RAM, which is a similar ratio. The thing is the scale.

*sheepish look* Welllll... let's not tell that to my 8GB FreeNAS VM that's serving up 4 x 6TB in RAIDZ2, eh. But it's only 53% full. So it is definitely the scale, but also the use to which it is put, and how full, and other things too.

But it really takes understanding the ins and outs of this stuff before it becomes ""safe"" to bend the rules, and even then, that 8GB VM can be spun up to 32GB with only a few keystrokes, or even 128GB in a different chassis.