Reasons of poor performance

[Recown]

Greetings! I found a little script on this forum, and it shows, that performance of my FreeNas is pretty low... Here is the result

[*]Media files, distributives, libs for dev
[*] 5:15PM up 139 days, 23:52, 1 user, load averages: 0.05, 0.04, 0.05
[*]1023MiB / 74.5GiB (freenas-boot)
[*]18.5TiB / 29TiB (tank)
[*]50.70GiB (MRU: 4.40GiB, MFU: 46.30GiB) / 16.00GiB
[*]Hit ratio -> 28.99% (higher is better)
[*]Prefetch -> 17.65% (higher is better)
[*]Hit MFU:MRU -> 22.08%:39.90% (higher ratio is better)
[*]Hit MRU Ghost -> 79.64% (lower is better)
[*]Hit MFU Ghost -> 14.30% (lower is better)

I cant find any detailed information about what is MRU and MFU Ghost. Just know, that it's some part of MRU and MFU areas of ARC cache.
Am i right, that the main reason is only 16GiB RAM for 18.5TiB storage?
P.S. I am sure, that FreeNas is great! I just want to understand what i am doing wrong...

 

[SweetAndLow]

Greetings! I found a little script on this forum, and it shows, that performance of my FreeNas is pretty low... Here is the result

[*]Media files, distributives, libs for dev
[*] 5:15PM up 139 days, 23:52, 1 user, load averages: 0.05, 0.04, 0.05
[*]1023MiB / 74.5GiB (freenas-boot)
[*]18.5TiB / 29TiB (tank)
[*]50.70GiB (MRU: 4.40GiB, MFU: 46.30GiB) / 16.00GiB
[*]Hit ratio -> 28.99% (higher is better)
[*]Prefetch -> 17.65% (higher is better)
[*]Hit MFU:MRU -> 22.08%:39.90% (higher ratio is better)
[*]Hit MRU Ghost -> 79.64% (lower is better)
[*]Hit MFU Ghost -> 14.30% (lower is better)

I cant find any detailed information about what is MRU and MFU Ghost. Just know, that it's some part of MRU and MFU areas of ARC cache.
Am i right, that the main reason is only 16GiB RAM for 18.5TiB storage?
P.S. I am sure, that FreeNas is great! I just want to understand what i am doing wrong...

Huh? Are those numbers bad? Please list what they should be or compare it to a similar system.

Sent from my Nexus 5X using Tapatalk

 

[MrToddsFriends]

Double posting

https://forums.freenas.org/index.php?threads/what-are-your-arc-statistics.28122/page-10#post-387408

My answer in that thread: No need to be concerned. FreeNAS versions prior to 9.10.2 showed a behavior that lead to spuriously high ARC hit ratios.

https://forums.freenas.org/index.php?threads/solved-differing-arc-usage-in-freenas-9-10-2.48831/

 

[brando56894]

MRU: Most Recently Used
MFU: Most Frequently Used

16 GB of RAM is pretty low for 18 TB, you're leaving yourself very little room for an ARC.

 

[Ericloewe]

MRU: Most Recently Used
MFU: Most Frequently Used

16 GB of RAM is pretty low for 18 TB, you're leaving yourself very little room for an ARC.

Huh? It's a very reasonable amount of RAM.

 

[SweetAndLow]

Huh? It's a very reasonable amount of RAM.

Agreed ram is just fine for most workflows.

Sent from my Nexus 5X using Tapatalk

 

[brando56894]

Huh? It's a very reasonable amount of RAM.

Isn't the "rule of thumb" about 1 GB/ TB? I didn't mean "low" as "detrimental", I just meant it doesn't leave a lot of room for an ARC.

 

[SweetAndLow]

Isn't the "rule of thumb" about 1 GB/ TB? I didn't mean "low" as "detrimental", I just meant it doesn't leave a lot of room for an ARC.

Those numbers are just made up and a good guide to go by. Anything after 16GB+ and it gets more flexible. The people trying to run 1-7GB of memory are going to have data loss.

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