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

rbid

Neophyte
Joined
Nov 16, 2015
Messages
10
@rbid, work at all? Work well? Work, but make users wait for seemingly forever?
Neat, I'm not concerned now with "performance", but "reliability".
I'm sure that the lack of memory may give a performance problem...
... but I'm not sure if this will lead to a reliability error... (That was the reason for my original question)

--- Ricky
 

solarisguy

Neophyte Sage
Joined
Apr 4, 2014
Messages
1,125
@rbid, it may crash with not enough of RAM, so in some sense reliability could be low.

Unless you are using encryption, your data would be safe though.
 

cyberjock

Inactive Account
Joined
Mar 25, 2012
Messages
19,526
Officially, we've never seen a crash that killed a zpool once you had 8GB of RAM, regardless of the zpool's size. However, I wouldn't go totally insane with trying to figure out how far you can go. I'd think that 6TB of storage with 8GB of RAM is probably safe, but before I ever added more storage I'd upgrade the RAM. You may not be too thrilled with the performance either, but you said you aren't concerned. :P
 

solarisguy

Neophyte Sage
Joined
Apr 4, 2014
Messages
1,125
@rbid, on my test system, I had 6 disks 3TB in RAID-Z2, with only 8GB RAM. I have upgraded to 16GB RAM, not because I have ever had an event I could even potentially attribute to having only 8GB of RAM, but because I did not want to have any problems.

I am using my test system for testing of my configurations, not FreeNAS/FreeBSD/ZFS limits or FreeNAS/FreeBSD/ZFS memory management code quality.

Good news is that 8GB covers a variety of scenarios, so you might be fine, but only to a point = bad news... And I had seen in computing over and over again, a user (a system) being fine for a very long time, but then data growing a little or a usage patterns slightly shifting and suddenly performance becoming abysmal, at a point when all the things that have to be in the physical RAM suddenly do not fitting there. Troubleshooting of such a condition is a nightmare, as initially RAM deficiency is often small and might go away for an extended period of time.
 

RichTJ99

Senior Member
Joined
Sep 12, 2013
Messages
376
Hi,

I read the PDF today & found it very interesting. I have a few questions - I hope this is the right place:


Vdevs - you cannot add more drives to a Vdev BUT you can replace all drives within the VDev with larger drives to expand the Vdev.
A vdev with a single drive is not safe for data in the event of failure.

A Zpool consists of Vdevs (single or multiple VDevs)
The Zpool is refered to as a volume

1. Why would you want more than one Vdev per freenas box if the concern is for data redundancy?
2. If you can have up to 11 disk in a Vdev, again why would you want more than 1 Vdev?
3. If you have a Zpool with 3 Vdevs (two 3x drives, one 1x drive) and the single disk Vdev fails, the entire Zpool is lost (right?)
4. How can I tell how much Ram the Freenas system is currently using?
5. How do I backup my Freenas config?
6. ZIL/L2ARC - Are these required for a home user environment?

My system -
Super Micro X10sl7-f
32GB ECC Crucial Ram
6x 2tb drives (testing)
Intel Xeon E3-1231V3

Thanks,
Rich
 

danb35

Wizened Sage
Joined
Aug 16, 2011
Messages
11,565
@RichTJ99, you're asking a bunch of unrelated questions, and some (if not most) of them would probably be better off in their own thread. With that said, here are some answers:
1. Why would you want more than one Vdev per freenas box if the concern is for data redundancy?
Because it's very convenient, in many cases, for all your storage to be together in one big volume. If you have secure vdevs (e.g., RAIDZ2) and good hardware, this is still safe.
2. If you can have up to 11 disk in a Vdev, again why would you want more than 1 Vdev?
Because you might have more than 11 disks, and/or you might buy disks at different times (6 now, 6 later), and/or you might be in an application where IOPS are critical, and therefore more vdevs give better performance.
3. If you have a Zpool with 3 Vdevs (two 3x drives, one 1x drive) and the single disk Vdev fails, the entire Zpool is lost (right?)
If any vdev fails, the entire pool is lost.
5. How do I backup my Freenas config?
http://doc.freenas.org/9.3/freenas_system.html#general
6. ZIL/L2ARC - Are these required for a home user environment?
Usually not.
 

Bidule0hm

Server Electronics Sorcerer
Joined
Aug 5, 2013
Messages
3,710
1. Because if you want more than 11 drives in your pool you'll need more than one vdev.

2. see 1.

3. Yes. That's why you don't want to add a single drive to a pool.

4. With the reporting tab in the GUI and/or with the top command.

5. Web GUI --> System --> General --> Save Config button

6. No. If you don't know if you need them then you very probably don't need them.
 

Mega Man

Member
Joined
Jun 29, 2015
Messages
55
@cyberjock i just reread this for like the 15th time and i noticed 1 thing i have a question about,

i use z3, you recommend 7/9/11 drives but " you can ignore this rule if this will be used to stream rips ect"

i have z3 and 6 drives, ( not sure how i missed this ) how would it affect me if i added another drive ( total of 7 ) ? i know i can overlook this, but should i ? i appreciate your time !

( this is just a home fileserver/ for streams ect, but i am still wrapping my head around everything as i have time to build is as follows
Intel Xeon E3 1231V3
MBD-X10SL7-F-O
(2)Crucial 16GB (2 x 8GB) CT2KIT102472BD160B ( total of 32gb)
(6)Seagate 4tb STBD4000400-- these are currently being phased out for WD reds-
Mushkin Enhanced ECO2 MKNSSDEC60GB mirrored boot drives
APC SMT1500 + AP9630 )

Just to clarify i know i will need to destroy this vdev / pool~ i can not add any disks ! but i can start over

that is fine like i said still in "beta" mode,

one more question more for my future planing i want to be able to dump and pull info relatively quick accross several pcs i know LACP is not going to increase speed ect, but that is just being done for fun ect- i have 4 ports aggregated besides 10GbE - how many mirrors or stripes ( i get those 2 confused - going to go read up on that ) do you recommend ?- or maybe a better question how much does read/write scale?
 
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Fredde

Member
Joined
Dec 7, 2015
Messages
58
Thanks for this explaning!

but just to clariy something, if you have, let say 6 hdds 2TB each, you can not add one more 2tb to that array? so if i want to add more hdds like 8x4tb i should create a new array? and if so, do i add them as a vdev or zpool? this is new for me and my english isnt the best! trying to build a server for personal use and wants todo it right from start/begining!

or can i create a zpool and add 2 vdevs to it?
 

Bidule0hm

Server Electronics Sorcerer
Joined
Aug 5, 2013
Messages
3,710
Yes, you can't add one drive like that (if you want to keep redundance). Yes, you need to destroy and recreate the pool.

For the vdev/pool differences look at the ZFS structure link in my signature ;)
 

cyberjock

Inactive Account
Joined
Mar 25, 2012
Messages
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The pdf is rigged up in some way that it only opens in the browser despite my setting telling the browser to hand pdfs off to Foxit for display.
Yeah, that's not an issue with my PDF. If you look at the link, it is NOT a link that ends in .pdf, hence your browser is doing exactly what you are telling it to do. It's also not my PDF because I didn't link you to a PDF file. I linked you to a google doc, which then open's in Google's document reader.

If you want to download the file you simply have to open that link, then click the download button at the top of the page.
 

MMacD

Member
Joined
Dec 12, 2014
Messages
55
Yeah, that's not an issue with my PDF. If you look at the link, it is NOT a link that ends in .pdf, hence your browser is doing exactly what you are telling it to do. It's also not my PDF because I didn't link you to a PDF file. I linked you to a google doc, which then open's in Google's document reader.

If you want to download the file you simply have to open that link, then click the download button at the top of the page.
Well, you call it a PDF. :D I took you at your word and presumed you were doing something tricky (which you are, just not what I thought).

And I'm afraid that it doesn't download. Google complains that it's too big to be scanned and asks whether I want to download it anyway. I click yes, and it ignores me.
 
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cyberjock

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Mar 25, 2012
Messages
19,526
Well, you call it a PDF. I took you at your word and presumed you were doing something tricky (which you are, just not what I thought).

And I'm afraid that it doesn't download. Google complains that it's too big to be scanned and asks whether I want to download it anyway. I click yes, and it ignores me.
Actually, that link you provided is called "PDF via Google Docs". There is a separate link called "PDF" that is exactly what you want if you want to download a PDF itself.

And I tried to download the file via the "PDF via Google Docs" link, which is exactly what you linked to above, and it worked on Monday as well as today. So again, something that has nothing to do with me.

Attention to detail my friend...
 

MMacD

Member
Joined
Dec 12, 2014
Messages
55
And I tried to download the file via the "PDF via Google Docs" link, which is exactly what you linked to above, and it worked on Monday as well as today. So again, something that has nothing to do with me.
Which browser? I'm using FF 43, and not having any problem downloading other docs including the FreeNAS manual pdf kindly provided by gpsguy.
 

cyberjock

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Mar 25, 2012
Messages
19,526
I'm using Firefox 43.0.4.
 

joeschmuck

Old Man
Moderator
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May 28, 2011
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I'm using FireFox 43.0.4 as well and had no problem opening nor downloading the PDF file.
 

bmcclure937

Member
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Jul 13, 2012
Messages
110
I have also opened without issue on Chrome (latest dev build, whatever that is).
 
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