Q: SLOG for All flash setup

[Caffe Mocha]

Hello everyone
I need some advice for my slog drive. initially, I was hoping to use optane 900 as slog but there are some issues with optane in FreeBSD.
https://redmine.ixsystems.com/issues/26508

my use case is presenting storage to ESXi via NFS & Iscsi

Question 1: Do I need a Slog drive if the setup is all SSDs? I know the most likely answer would be Yes , which would lead to
Question 2: What would be a suitable and yet compatible Slog drive?

the set up is
Motherboard X10DRH-CT with intel E5-2650Lv4 with 4 core dedicated to FreeNAS
RAM: 64G
HBA: IBM M1215 flashed to IT mode
Optane 900 280G <-----no longer a option due to compatibility issue
SSD Micron S630DC 960G x 8

 

[nightshade00013]

It honestly depends on the way you have the SSD's set up. They are already very fast so if they are setup as multiple mirrored vDev's in a single pool I doubt you will see a ton of benefit from adding a SLOG. I am making a guess that you are virtualizing FreeNAS as well.

But it all depends on how the performance currently is. If this is hypothetical and you don't have the system up and running you need to put it into use and see if there are issues. If not sinking money into a slog probably will not help much and you will not know until you start hitting it with loads. Also since you are going all flash adding more vDev's in would make a SLOG obsolete anyway and likely at a cheaper cost since the only thing you would be able to look at is something like a Intel Optane P4800X which properly setup as a SLOG will set you back around 3000 + for what I would see as a minimal performance boost unless there are a ton of sync writes.

 

[Caffe Mocha]

I don't have the system set up yet
. Maybe I should try to set up the system first and do some benchmarks.
Preferably use raid z2 or raidz 1 . What would you recommend ? I have read that ssds is able to resilver much faster than traditional HD. So raidz 1 is sufficient


Sent from my Pixel 2 using Tapatalk

 

[nightshade00013]

Depends on the backups being made among other things. But that is part of the deal with testing, get the system setup and I would personally do a RaidZ2 first then try a RaidZ1 with two vDev's and then just multiple mirrored vDev's.