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Slideshow explaining VDev, zpool, ZIL and L2ARC for noobs!

Yorick

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Nov 4, 2018
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I guess that depends on how you define "bug." It's probably behaving as intended, but "as intended" is, well, not very good behavior. The pool configuration @kivalo is considering is not optimal or recommended, but that doesn't mean it's always a bad idea, and to prevent such configurations entirely with no possibility of bypassing the warnings doesn't seem like a very good idea--particularly when every previous version of FreeNAS has allowed for this (after appropriate warnings).
I'll quibble about "prevent such configurations entirely" - "zpool create raidz2 poolname dev1 ... devN" is still a thing. Anyone who runs that from CLI clearly meant to do that, whatever the (sub-optimal) outcome.

Without knowing how many people inadvertently, and warnings notwithstanding, created a vdev configuration they didn't mean to create, it's hard to make a judgment call on whether the pros of this change - keeps GUI users from shooting themselves in the foot - outweigh the cons: Need to drop to CLI to create mixed-disk-size vdevs.
 

naven

Newbie
Joined
May 4, 2020
Messages
1
Good afternoon!

Installed Freenas... While I like everything, but I am not familiar with *nix systems, with the ZFS file system, and I would like to ask a few questions about the stability of such a storage. Say I have a pool of one hard drive. Can I insert this disk into a new computer with freenas installed from scratch and access the data? It's just that all these utilities are snapshots, pools, etc. - I can’t understand if the disk will work, as, say, I would insert a disk with ntfs or fat in a new computer.
 

danb35

Wizened Sage
Joined
Aug 16, 2011
Messages
11,760
Can I insert this disk into a new computer with freenas installed from scratch and access the data?
This seems an odd place to be asking the question, but yes--just import that pool into the new installation.
 

rreboto

Neophyte
Joined
Dec 8, 2020
Messages
4
Everyone that has used non-ECC RAM and the RAM went bad suffered a loss of their entire pool. Unfortunately, because of how everything works, it'll trash your original copy of the data, which will trash the backups too.
I'd appreciate clarification what you are emphasizing here:

Bad RAM will destroy your original copy and your backup!

Does this apply to snapshots as well? It has been my understanding thus far that snapshots are read-only, and if you have at least one snapshot from the time before RAM went bad, it would be possible to restore good data from a snapshot. So, if the backup server is keeping snapshots, there is still a chance that the data is in a safe, recoverable state.

Thanks!

PS: There's a lot of great information in the deck; thanks for putting it together!
 

danb35

Wizened Sage
Joined
Aug 16, 2011
Messages
11,760
Bad RAM will destroy your original copy and your backup!
Well, if bad data is written, and once written, that bad data is backed up, the backup is going to be bad as well--which is why you'd want to keep a history of backups.
 

Fox

Member
Joined
Mar 22, 2014
Messages
53
I've had bad ram on a client (non-freenas) copy files to and from the NAS and thus corrupt them in the process. In this case, freenas snapshots would work to correct it if you catch the issue before the snashots roll off the server. I was lucky I caught it early due to other system errors.

The next client computer I buy/build, I will only have ECC memory.. Never again..
 

rreboto

Neophyte
Joined
Dec 8, 2020
Messages
4
I've had bad ram on a client (non-freenas) copy files to and from the NAS and thus corrupt them in the process. In this case, freenas snapshots would work to correct it if you catch the issue before the snashots roll off the server. I was lucky I caught it early due to other system errors.

The next client computer I buy/build, I will only have ECC memory.. Never again..
Thanks @Fox. Sounds like you are confirming that snapshots prior to RAM going bad will still be good. And, yes, understood: once the good snaps roll off, you're in a bad spot.
 

jgreco

Resident Grinch
Moderator
Joined
May 29, 2011
Messages
13,198
Thanks @Fox. Sounds like you are confirming that snapshots prior to RAM going bad will still be good. And, yes, understood: once the good snaps roll off, you're in a bad spot.
Well, it's also possible, if the memory corruption is an ongoing thing, for the snapshot to be good on disk but corrupted when read into memory to be handed off to you. There's been a lot of handwringing about the value of ECC over the years, and a lot of authoritative people saying this and that stupid thing. The simple fact of the matter is that if you shovel data around on a system with potentially bad RAM, you can potentially get garbage. This isn't a ZFS thing, it's basic computer science and the reason servers are generally designed with ECC.
 

Fox

Member
Joined
Mar 22, 2014
Messages
53
Thanks @Fox. Sounds like you are confirming that snapshots prior to RAM going bad will still be good. And, yes, understood: once the good snaps roll off, you're in a bad spot.
My problem was on the client only.. I would copy stuff to the NAS and the files would not compare. With bad ram on the NAS, I shudder to think what could happen.. I could think of a few scenarios where things go sideways.. Like a scrub, where it thinks there is an error on the disk and then it tries to correct it.. I am not sure if that repair would be at a low level, like fixing a bad block on the disk, or at a higher level, like a copy on write. If it did happen at a low level, I could picture the NAS "fixing" (corrupting) what it thinks is a bad block, and that block contains part of a snapshot.

But I am not an expert on ZFS... Bad memory is very rare, but In my experience, Ive had it happen with a DDR type memory stick a few years ago, which the manufacturer replaced free under the lifetime memory warranty. I have also had it happen many many years ago to a on-board CPU cache. This was back in the day when the CPU cache was not in the CPU (like L3).. In that case I was able to isolate the actual chip, which was luckily not soldered in, and then went to Fry's Electronics and bought another chip and pushed it into the slot to fix the problem.. Both times I experienced a very flaky system.. Random blue-screens, reboots, corrupted files, etc.... Stuff like that. It's not fun..
 

Yorick

Dedicated Sage
Joined
Nov 4, 2018
Messages
1,743
Both times I experienced a very flaky system.. Random blue-screens, reboots, corrupted files, etc.... Stuff like that. It's not fun..
I had bad memory maybe twice, max thrice in the last 20 years - and it was a complete clusterfsck of a week+ of troubleshooting to narrow it down to memory, each time. Never. Again. Now that AsRock/Ryzen is a thing, I'm building ECC desktops only.
 

NASbox

Senior Member
Joined
May 8, 2012
Messages
546
I had bad memory maybe twice, max thrice in the last 20 years - and it was a complete clusterfsck of a week+ of troubleshooting to narrow it down to memory, each time. Never. Again. Now that AsRock/Ryzen is a thing, I'm building ECC desktops only.
I'm curious:
What kind of a premium do you have to pay for an EEC build vs Non-ECC?

Also, what is the quality of Asrock borads? I was under the impression that they used Chinese caps vs Japanese caps, which can make quite a difference to motherboard life. (Or am I mistaken about this?)

If you are tuning the hardware every 2 years, then maybe it doesn't matter, but I tend to keep my hardware for quite a long time.
 

Yorick

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Joined
Nov 4, 2018
Messages
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I'm curious:
What kind of a premium do you have to pay for an EEC build vs Non-ECC?
Also, what is the quality of Asrock borads? I was under the impression that they used Chinese caps vs Japanese caps, which can make quite a difference to motherboard life. (Or am I mistaken about this?)


ECC is dirt cheap, maybe 10-15 USD more per stick.

Er caps. Haven’t thought on that. Let me see what the Internet says! Okay from a quick sampling, every AsRock board I looked at claims “100% Japan made high quality conductive polymer capacitors”.

I’m with you on longevity. We replaced the husband’s PC after 10 years of service. I’m trying to make it to 10 years as well, which is 2022. Just have to have the discipline and not jump on that AM5 when it’s released in 2021 :).
 

NASbox

Senior Member
Joined
May 8, 2012
Messages
546
ECC is dirt cheap, maybe 10-15 USD more per stick.

Er caps. Haven’t thought on that. Let me see what the Internet says! Okay from a quick sampling, every AsRock board I looked at claims “100% Japan made high quality conductive polymer capacitors”.

I’m with you on longevity. We replaced the husband’s PC after 10 years of service. I’m trying to make it to 10 years as well, which is 2022. Just have to have the discipline and not jump on that AM5 when it’s released in 2021 :).
That's good to know... I was under the impression that Asrock was a "cheap" "off" brand owned by Asus... they used some of the engineering from the name brand Asus boards, but cut corners and used lower cost/quality parts. If my impression is wrong, I'd love to hear feedback from the community as I would likely consdier buying one at some point.
 

Ericloewe

Not-very-passive-but-aggressive
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Feb 15, 2014
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16,830
The similar names are just a coincidence.
 

NASbox

Senior Member
Joined
May 8, 2012
Messages
546

Yorick

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Nov 4, 2018
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ASRock was spun out from Asus in 2002. It's now a competitor in the motherboard space. You can read a bit about their history here: ASRock - Wikipedia

Pegatron, who own ASRock, were also spun out from Asus.

ASRock was originally created to make motherboards for the value OEM market, but started moving "upstream" in 2007 and have a good reputation in the DIY/enthusiast market now.
 
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