Tips for ZIL and L2ARC usage (yes or no and how)

[jackydany]

Hi alltogether,

i am just building my "new" freenas server. Going to be an Xeon E5-26xx with 2ghz and 4 cores.
32gb Ram, maybe 64.
I bought a cheap sun F20 flashcard. It has 4x 24gb SSD on it. They are straight passed thorugh to freenas.
These cards are made for acceleration via flash. Although they are older, the price of 20€ was worth the fun :D

My plan is to use them as followed:
2x 24gb mirrored root installation device
2x 2gb of the other 2 SSD for ZIL and the remaining 2x 22gb for L2ARC.

Is it possible and helpfull to mirror the ZIL? I read a lot but i am still a bit confused about all this ZIL, SLOG, L2ARC stuff :D
I want to partition the 2x24gb ssd to have a mirrored ZIL and a non mirrored 2x22gb=44gb L2ARC.

As Storage i have a NetApp DS4246 with 12x 2tb sas drives via an 9201-16e LSI HBA in IT-Mode.

This Freenas Server will serve as Data-Storage for Pictures, Movies etc. Music as well as Software Binaries.
There will be no VM running on the system or storage.
It will replicate to another freenas server (later on) and vice versa.
Also it will funcion as storage for multiple security cams.
My VMs running on a proxmox host will connect to freenas to show galeries and host webpages stored on freenas.
The VM;s will be backed up to the freenas.
I plan to have a VM running emulators and the ISOs and other stuff will be stored on the freenas (wip).
The storage on the DS4246 will be extended one day, still have 12 slots free ;)

Could you give me some hints what would be the best idea to use this card?

Thanks in advance

Stefan

 

[K_switch]

@jackydany

I am interested to see how this configuration works out in the end. My understanding is as it is possible to mirror the SLOG (ZIL or zfs intent log is more the technology where SLOG or separate log is the actual disk when not in pool) you would be better off leaving it un partitioned or using a stripe.

 

[jackydany]

as far as i read about this, mirroring the slog would be better as this is "write cache" not written to disk yet (not really a cache i know that!).
but l2arc is "only" read cache. there are different opinions about hits

Time to Reevaluate the "Mirror your Slog (ZIL Drive)" recommendation?

Seemingly the rest of the ZFS community outside of FreeNAS has done just this. Back in the v15 pool days, it was CERTAINLY a good idea to mirror your SLOG, as if you lost it your pool was garbage. These days this is no longer the case, but for some reason FreeNAS still recommend this as best...

www.ixsystems.com

SLOG Devices

Provides general information on ZFS intent logs (ZIL) and separate intent logs (SLOG), their uses cases and implementation in TrueNAS.

www.ixsystems.com

- 45Drives Knowledge Base

Click here for instructions you need to get your Storinator(s) up and running. Disclaimer The information contained in the articles comprising the 45 Drives Knowledge Base (KB) have been verified as up-to-date on the date of the original publication of the article. While 45 Drives endeavors to...

www.45drives.com

How to build SSD RAID0 for L2ARC cache

Hi Everybody here, I have a small question. How to build SSD RAID0 for L2ARC cache in FreeNAS by command line or GUI? Thanks I want to test the IOPS and multi user read performance. I have 2 Samsung 860evo 500gb SSD. Thanks a lot advance.

www.ixsystems.com

my main goal is not the mega heavy performance boost but a little boost for my freenas (4x 1gbit and 1x 10gbit ethernet), later i want to do the same on my proxmox host running on ZFS as well.
most important for me is always the data integrity and security. on this server are my memories stored, picutres, videos, documents etc. safety is always more important than performance

 

[HoneyBadger]

The good news is that your plan to use a pair of those flash modules for mirrored boot is perfectly sound. They're not very fast compared to a modern SSD but should be rocketships compared to a cheap USB stick.

However, they aren't fast enough to be viable SLOG devices on their own, and sharing a device between SLOG and other use makes it do a horrible job at both. They could potentially be worthwhile as L2ARC but to be perfectly honest it doesn't seem like your workload demands much in terms of caching.