My FIRST TIME IN TrueNAS (HELP!!)

[jgreco]

Good point, "copies=2", (or 3), would only help on RAID-Z1, if their were 2 or more RAID-Z1 vDevs. ZFS is supposed to write the second copy to another vDev, if possible.

Yes, that's true. I wonder how often this is actually done in the real world though. ZFS already stores several copies of critical metadata (and if memory serves does spread it amongst vdevs). The primary practical use for copies= would appear to be data stored on a single hard drive (or maybe a pure stripe of several hard drives). Making twitchy failure-prone RAIDZ1 vdevs and then relying on copies= instead of robustly designed vdevs for redundancy seems like it would be wasteful of raw space, and it would be better to just go with a wider vdev and RAIDZ2 or RAIDZ3. Just goes to show you all the weird things you can do with ZFS.

 

[Constantin]

L2ARC is 97% misses, which isn't quite as terrible as one might think. This would probably warm up further under regular usage.

Comes down to use case, no? L2ARC that is persistent AND metada-only can really speed things up as I demonstrated in my testing. Switching to a special VDEV only increased speeds marginally, and that again came down to use case. A rig hosting a DB with tons of little files would surely benefit more from a special VDEV than a persistent metadata-only L2ARC.

That's the thing about Free/TrueNAS... it allows the admin to get pretty close to the metal and as such also requires some careful thought re: what to buy, why to buy it, followed by how to configure the system, etc. TrueNAS is not a Synology/ReadyNAS/QNAP "Oh don't worry your pretty little head" solution where someone else makes these decisions and hides a great deal of complexity behind a couple of buttons. The target audience is different, so is the solution.

 

[Arwen]

I would not suggest using "copies=2" with RAID-Zx, except for critical datasets. If the whole pool needs better redundancy, then bumping up the RAID-Zx level to 2 or 3 is the correct path. (Or increasing the number of Mirrors in vDevs, when using Mirrored vDevs.)

 

[gianfelicevincenzo]

Excuse my absence.

Finally decided to remove the L2ARC disk as, at present, it seems really useless to me. I added new HDDs and fixed the existing ones. Right now I have 8 sata ports occupied. A question: Let's say that a disk breaks (in the future) ... how do I connect the new disk to be able to recover / copy data from the "broken" disk (no longer having sata ports available)? I might think about removing (temporarily) the Plugin pool disk...

 

[Davvo]

You don't recover anything from the "dead" disk, you follow this steps.

Disk Replacement

Describes how to replace a disk and restore the hot spare in TrueNAS CORE.

www.truenas.com