SLOG question

[Octopuss]

How do I know if I get any sync writes with the way I use my NAS? I've read a few articles, but since I don't understand any of the technical stuff and Linux especially, I can't tell.

 

[Chris Moore]

The good news then, FreeNAS doesn't use Linux. FreeNAS uses FreeBSD (Unix) for the operating system. Here are some links to threads that are all about SLOG devices, they probably have some good information in there if you take time to read:

The ZFS ZIL and SLOG Demystified
https://www.ixsystems.com/blog/zfs-zil-and-slog-demystified/

Some insights into SLOG/ZIL with ZFS on FreeNAS
https://www.ixsystems.com/community/threads/some-insights-into-slog-zil-with-zfs-on-freenas.13633/

Testing the benefits of SLOG using a RAM disk!
https://www.ixsystems.com/community/threads/testing-the-benefits-of-slog-using-a-ram-disk.56561/

SLOG benchmarking and finding the best SLOG
https://www.ixsystems.com/community/threads/slog-benchmarking-and-finding-the-best-slog.63521/

 

[Octopuss]

I briefly checked most of these articles I believe, but I'm still not sure at all.
My FreeNAS is basically used as a storage for a torrent seedbox and for backups from the computers at home (running Windows).
I just couldn't figure out if I could benefit from SLOG at least a little.

 

[Rand]

How about you observe current performance to establish a baseline.
Then you change the dataset to sync=disabled (preventing any sync writes) and see if things get faster that ways.
If they do then you have sync writes which would benefit from a slog, if there is no change then your writes are async to start with...

 

[Chris Moore]

I briefly checked most of these articles I believe, but I'm still not sure at all.
My FreeNAS is basically used as a storage for a torrent seedbox and for backups from the computers at home (running Windows).
I just couldn't figure out if I could benefit from SLOG at least a little.

SLOG is all about synchronous write. If you are not writing to the pool, it isn’t being used at all.

What type of network share do you have? NFS, SMB, iSCSI?

The way you are using the system “seed box” doesn’t say anything about how your communication is handled at the level that matters, but it does imply that it is mostly reading, not writing. Are you downloading torrents also?

If most activity is reading the pool, your best upgrade might be more RAM followed by L2ARC.

You could give more details about the system to help us help you.

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[HoneyBadger]

How do I know if I get any sync writes with the way I use my NAS?

During a period of writes to your NAS, open a shell/SSH session and run zilstat -t 5 - if it's zeroes across the board you are not generating sync writes. No sync writes = no benefit from SLOG.

 

[Octopuss]

Thanks.
Looks like absolutely zero even when the seedbox is downloading stuff.

 

[Chris Moore]

Thanks.
Looks like absolutely zero even when the seedbox is downloading stuff.

That is the reason I asked how you are connecting with the storage. How you access the storage tells a lot about how the system needs to be configured. I have seen a lot of people buy hardware they just don't need.

 

[Octopuss]

Well the seedbox is a linux server that has a NFS share on the NAS, so I thought it could be hypothetically useful at least for that.

 

[Chris Moore]

Well the seedbox is a linux server that has a NFS share on the NAS, so I thought it could be hypothetically useful at least for that.

Usually, a NFS share would be sync data. There could be a setting somewhere that is preventing it from working that way. Can you give more details?

 

[Octopuss]

I'm not sure what kind of details since I don't understand linux-like technical stuff.
Both FreeNAS and the torrent server are VMs in one physical server. The torrent server is running Ubuntu server 19.10.
There's a NFS share on the NAS.
There are actually two identically named shares, one for the torrent server, and one for Windows. Not sure if that matters.