My Zil/L2arc questions

[Ianm_ozzy]

Hi all

I have various extra hardware to possibly use to improve performance.

I ordered a quad port nic from ebay & have one already. They are fairly cheap.
I have one machine that needs fast network access to will use teaming to speed things up.
1 gigabit is too slow and 10 gigabit is expensive overkill.

So I have other hardware to be used if it will improve performance.

2 x old 60GB SSDs
2 more recent 240 GB SSDs.
They can be swapped to/from machines.

I store large media files and many smaller files.
When I sync across the network to my NAS it can be slow, especially when small files are involved. I typically use ubuntu OS with freefilesync for that.
Some datasets have sync on and some off.
Ideally they should all be on and would like that to be the case.

Will the 60 GB drives in mirrored configuration as a ZIL be a benefit. They are both Kingston V300 60 GB drives.
There are inexpensive 16GB intel optane drives available.
That is another option to use as a ZIL.
If I do that the 60GB drives could maybe be used as an L2ARC in striped configuration.



In my gaming machine I have a 256GB NVMe which a may use as an L2arc when replaced.
There are many different opinions as if that would be a benefit.

I have some virtual machines running also. - Windows 10, ubuntu server with network related activity always on & another ubuntu server specifically as a game cache.
I am looking to maybe have pfsense also as a virtual router.
That would mean around 8GB of RAM will allocated.

It is a home server with nothing critically important on there.
Everything is backed up on external hard drives.

Is a 16GB optane drive as ZIL benefitial?
Are 2 60GB SSDs mirrored useful as a ZIL?

Will they improve performance for my hard drive based Pool?


Thank you

 

[Spearfoot]

Hi all

I have various extra hardware to possibly use to improve performance.

I ordered a quad port nic from ebay & have one already. They are fairly cheap.
I have one machine that needs fast network access to will use teaming to speed things up.
1 gigabit is too slow and 10 gigabit is expensive overkill.

So I have other hardware to be used if it will improve performance.

2 x old 60GB SSDs
2 more recent 240 GB SSDs.
They can be swapped to/from machines.

I store large media files and many smaller files.
When I sync across the network to my NAS it can be slow, especially when small files are involved. I typically use ubuntu OS with freefilesync for that.
Some datasets have sync on and some off.
Ideally they should all be on and would like that to be the case.

Will the 60 GB drives in mirrored configuration as a ZIL be a benefit. They are both Kingston V300 60 GB drives.
There are inexpensive 16GB intel optane drives available.
That is another option to use as a ZIL.
If I do that the 60GB drives could maybe be used as an L2ARC in striped configuration.



In my gaming machine I have a 256GB NVMe which a may use as an L2arc when replaced.
There are many different opinions as if that would be a benefit.

I have some virtual machines running also. - Windows 10, ubuntu server with network related activity always on & another ubuntu server specifically as a game cache.
I am looking to maybe have pfsense also as a virtual router.
That would mean around 8GB of RAM will allocated.

It is a home server with nothing critically important on there.
Everything is backed up on external hard drives.

Is a 16GB optane drive as ZIL benefitial?
Are 2 60GB SSDs mirrored useful as a ZIL?

Will they improve performance for my hard drive based Pool?


Thank you

Remember that ZIL/SLOG is not a cache; a ZIL/SLOG device isn't going to improve performance. If you're not running enterprise-critical virtual machines or databases you'll probably be happier disabling synchronous writes as this will give you the best possible performance from your hardware. That said... if you really want to use a ZIL/SLOG there are several threads here on the forum addressing the question of what makes a good choice for this purpose. These should have power protection and be as fast as possible with low latency. But again -- despite using the most optimal ZLI/SLOG device, you're never going to get write speeds anywhere close to your read speeds.

How much memory does your FreeNAS system have? The general rule-of-thumb is to install maximum supported memory before installing an L2ARC; RAM is always faster than disk.

 

[jgreco]

Some insights into SLOG/ZIL with ZFS on FreeNAS

What is the ZIL? POSIX provides a facility for the system or an application to make sure that data requested to be written is actually committed to stable storage: a synchronous write request. Upon completion of a sync write request, the underlying filesystem is supposed to guarantee that a...

www.ixsystems.com

 

[SweetAndLow]

None of those things including adding more network card will help your performance.

 

[Ianm_ozzy]

Remember that ZIL/SLOG is not a cache; a ZIL/SLOG device isn't going to improve performance. If you're not running enterprise-critical virtual machines or databases you'll probably be happier disabling synchronous writes as this will give you the best possible performance from your hardware. That said... if you really want to use a ZIL/SLOG there are several threads here on the forum addressing the question of what makes a good choice for this purpose. These should have power protection and be as fast as possible with low latency. But again -- despite using the most optimal ZLI/SLOG device, you're never going to get write speeds anywhere close to your read speeds.

How much memory does your FreeNAS system have? The general rule-of-thumb is to install maximum supported memory before installing an L2ARC; RAM is always faster than disk.

Firstly I am upgrading my network speed. That is limiting factor when it comes to copying large files.
Also all storage is on hard drives.
The machine has 32GB and is the maximum.
I will be switching from windows shares to nfs as I use linux mainly.
Anything from windows I need to back up/syncronise I will do through linux as the machine accessing will be a dual boot machine.

The NAS It has DDR3 non ECC memory so I do not want data intended for disk writes hanging around in memory for long.

So as I understand it, it will be best to have sync set to always for all datasets if you want data committed to disk when written.
That can be slow writing many small files and it has been.

So I could use a couple of old SSDs in a mirrored config as a ZIL maybe.
I was curious about intel optane drives. I can maybe get 16GB one for not much money and use as a ZIL.
So the read/write speeds are mediocre. The responsiveness is much higher than a NAND drive and apparently has greater endurance.


When backup up/sycning to the NAS, there is a large variety of file sizes. When wring the smaller ones, then things can slow down.

So for that setup will the intel 16BG optane improve overall write speeds, when using NFS and sync set to always?

As for L2ARC i will give it a try and see if it causes issues. A suitable ZIL is more important.


Thank you

 

[jgreco]

Please read the link I posted before.

The fastest disk writes are to avoid sync writes. Adding a SLOG is always slower than simply disabling sync. The SLOG/ZIL is *not* a cache of any sort.