My FIRST TIME IN TrueNAS (HELP!!)

[gianfelicevincenzo]

Hi. I'm new to truenas/zfs and honestly I don't know how to do it (too much information...too little information!). I have 4 Seagate IronWolf HDDs (2TB each). In addition I have two SSD 860 Evo Samsung: The system is installed on one ssd (250GB) the other ... I still don't know what to do with it (500GB). What disk configuration do you recommend? Raidz with Metadata on SSD? Logs?
I've also seen various settings that I honestly still don't quite understand what they are: "Auto Trim" should I enable it (since I can have an SSD in the pool)? Record Size on a 4TB configuration, what value should it be set to? Thanks, I hope some expert of you can help me.

 

[Arwen]

First off, RAID-Z1 is not recommended with 2TB or larger disks. During disk replacement, if a problem on one of the 3 remaining disks occurs, you can have data loss.

ZFS does do something different on block loss, (verses entire disk loss), it will tell you the file(s) affected. And standard metadata has 2 copies by default, so less likely to affect an entire directory structure.

Using a single SSD for metadata and having redundancy on the regular pool is not a good idea. The general rule of thumb is that special metadata vDevs should have the same redundancy amount as the regular data vDevs. Thus, if using RAID-Z1, (which has 1 disk of redundancy), you would use 2 SSDs mirrored as the special metadata vDev.


In the case of 4 x 2TB disks, RAID-Z2 is a good compromise. You can loose any 2 disks and not loose any data. You can setup the free SSD as a L2ARC for metadata, (which has it's main copy on RAID-Z2, so no concern about loosing it).

It would be a good idea to read up on ZFS. It is pretty different from many other RAID & file systems.

It would be helpful to know the rest of your hardware, as well as your use case.

 

[Davvo]

Welcome! I suggest you reading the two following resources in order to start diving into TrueNas and ZFS.

Introduction to ZFS

This is a short introduction to ZFS. It is really only intended to convey the bare minimum knowledge needed to start diving into ZFS and is in no way meant to cut Michael W. Lucas' and Allan Jude's book income. It is a bit of a spiritual...

www.truenas.com

Hardware Recommendations Guide

This is the latest edition of the FreeNAS Community hardware recommendations guide. The current major version is R2, dated January 2021, with the last minor update on 2021-01-24. The format has moved away from the forum post form factor, to...

www.truenas.com

Two mirrors (each composed of 2 HDDs) could be a better layout than a single RAIDZ2 vdev (and it might be a requirement if you want to do a few things) since it allows better flexibility. Also, you did not share your full hardware specs, as well as your objective/use case, which is something you want to do every time you open a thread on this forum in order to get better help.

Record size depends on what kind of file you want to store in that dataset... rule of thumb is to increase for videos and other incompressible files.

 

[gianfelicevincenzo]

My use case is mainly data sharing/backup in my network (pc win, linux, etc.), therefore with SAMBA. As for L2ARC I read that you need a lot of ram...so, can I use L2ARC? In any case, what are the benefits?

- CPU i3-6100 (3.7GHZ, TurboBoost)
- 2x4GB (DDR4, dual channel)
- 4x2TB (Seagate IronWolf 5900 RPM)
- SSD 860 EVO 500/250GB

As for the raid I chose to use the raidz because I don't want to lose half the usable capacity (unfortunately I can't afford other hdds, and in my case I have reached the maximum sata and pcie ports). But since it's not; a corporate network with 1000 employees, I could be comfortable with this mode, right? (I also very often check the parameters of all disks looking for problems)

 

[Davvo]

RAIDZ1 with 2TB drives can still be considered acceptable. Just do know that if you lose more than one drive your pool fails.
Do note the required minimum RAM is 16GB.

 

[ChrisRJ]

@vincentj , did you read the linked resource provided by @Davvo ? ZFS was created for large enterprise storage systems. So it behaves differently in some aspects to what you are used to.

 

[gianfelicevincenzo]

Yes, i'm reading those resources...as for the ram, i can always change it (currently i'm sticking to these). What about the L2ARC cache? I have an unused 250GB SSD. What benefits could I get?

 

[Samuel Tai]

With only 8 GB of RAM, you won't see any benefit to L2ARC. You should upgrade to 16 GB, which is the minimum required for TrueNAS.

 

[gianfelicevincenzo]

Hi samuel.
What could I achieve by increasing the ram to 16GB with L2ARC? Is it worth it from the current situation with 8GB ram WITHOUT L2ARC?

 

[Samuel Tai]

It depends on your workload. Some folks here don't see any benefit to L2ARC until they hit 128 GB of RAM. In my use case, I do see a small benefit to L2ARC on 16 GB RAM when enumerating directories containing >= 1000 photos over SMB. Without L2ARC, thumbnail generation is noticeably slower than with L2ARC. However, you want your L2ARC interface to be as fast as possible. Using a SSD over SATA, you probably won't see any benefit. I have an Optane over PCI-E for my L2ARC.

 

[Arwen]

Using RAID-Z1 with 4 x 2TB disks can work, if:

• You understand that loosing more than 1 disk, looses the pool
• Loosing a block(s) while replacing a disk means you loose a file or more, (which can be restored from backups)
• Using TrueNAS for sharing files is not a backup for those files

With limited memory, <=16GB, a L2ARC is not suggested. (Even if it was limited to metadata.)

 

[Whattteva]

RAIDZ1 with 2 TB disks are fine as long as you do regular scrubs and monitor SMART results in my opinion, though I would probably not do it with more than 4 drives max. Resilvering a 2 TB drive even at 80% pool capacity is probably only going to take 4-5 hours max,

 

[Davvo]

Hi samuel.
What could I achieve by increasing the ram to 16GB with L2ARC? Is it worth it from the current situation with 8GB ram WITHOUT L2ARC?

You should have at least 16GB of RAM regardless of L2ARC.

 

[gianfelicevincenzo]

I managed to add another 8GB of RAM (for a total of 16GB). In the graph I noticed that maximum 12.4/12.6GB of ZFS cache are occupied, but when I try to see the RAM it is barely 2 GB...why? Regarding L2ARC, @Samuel Tai, are the benefits only noticeable with the "reading" of many photos?

A last question. I've read that ZFS also provides SLOG/ZIL. The question is: in the GUI Web when I specify the VDEV, what is the SLOG?

 

[Samuel Tai]

SLOG/ZIL is a log VDEV device, and you probably don't need it you're not serving iSCSI drives to vmWare ESXi hosts running thousands of VMs. It's basically a scratch device for writes that has a small power reserve (for power outages) to enable quick writes to the scratch space, which can then be echoed back to the data VDEVs at a (slightly) later interval. Its purpose is to reduce write latency to the pool.

 

[jgreco]

With limited memory, <=16GB, a L2ARC is not suggested. (Even if it was limited to metadata.)

All you folks are mistyping "16GB" instead of "64GB" in this thread. As a general rule of thumb, the ARC needs a substantial amount of elbow room to categorize cache entries by MFU/MRU, and the general consensus of those who have experimented with it is that this usually doesn't become meaningful on a real workload until about 64GB of ARC. Additionally, since L2ARC consumes some ARC for the pointer records, if you want to add a 250GB L2ARC device, you really do want 64GB of ARC. There are some special cases where this might not be true, such as highly cacheable workloads or metadata-only L2ARC.

 

[gianfelicevincenzo]

Thanks @Samuel Tai. So, I guess this thing is set up via the CLI, right? Because in the vdevs I don't see the SLOG entry...

 

[gianfelicevincenzo]

@jgreco so, is it useless to add this SSD as cache?

 

[Samuel Tai]

@vincentj, for your first build, keep things simple. You can add other VDEVs later, but you'll need a baseline for comparison first. A common mistake first NAS builders make is to try for max performance first. You actually want to optimize for reliability first.

 

[gianfelicevincenzo]

@Samuel Tai Maybe you're right.
But in reality I'm not looking for very high performance (also because my network currently doesn't allow me... gigabit). Most of all I wanted a good compromise between security/throughput/speed (more throughput) and since I move very often small files, I wanted to somehow speed them up...