# FreeNAS 8 - best disk configuration



## reezin14

RAIDZ1 imo would be your best bet drives x3 1TB with 2TB usable space with some protection encase of 1 hard-drive failure.Or use 3/4 500GB drives(RAIDZ1 or RAIDZ2),just depends on how much space you think you'll need.And yes raidz is best when using drives of the same size.Be sure to have a minimum of 6GB+ of RAM as ZFS uses a lot. More info can be found here and here.In the first link scroll down to RAID Overview to help you get a better understanding of what you might want to go.


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## michael_sj123

Thanks for the links, guess my mind crapped out when I was searching! Answered a lot of my questions though I still have a few. I am thinking of going 4x 1TB in RAIDZ2, how will my write/read speed look like then? I also would like to know if I can purchase say 4x 1TB disks at a later date and add them to the array - as I did some searching and it seems like you cannot add one disk at a time, either I must upgrade the entire array or buy the same amount of disks and add them, is that correct?


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## reezin14

Your read/write speeds would depend on a few things such as hard-drives,network nics,settings etc.... So the only why to find out would be to run some test.You are correct ZFS doesn't allow you to just add one disk at a time to vdev,but you can stripe a new vdev to expand the size of a pool.Info here(Volume Manager after a Volume has been Created). Hope this helps.


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## Plan9

You don't need as much as 6GB of RAM, 4GB would easily be enough. But when RAM is cheap, there's no harm in going over.

As for the disk configuration, I'm running two 3x 1TB HDDs in raidz1 :

Code:



Code:


pool: zprimus
 state: ONLINE
 scrub: scrub completed after 5h56m with 0 errors on Wed Jul 11 06:57:18 2012
config:

 NAME        STATE     READ WRITE CKSUM
 zprimus     ONLINE       0     0     0
   raidz1    ONLINE       0     0     0
     ad10    ONLINE       0     0     0
     ad14    ONLINE       0     0     0
     ad12    ONLINE       0     0     0
   raidz1    ONLINE       0     0     0
     ad2     ONLINE       0     0     0
     ad4     ONLINE       0     0     0
     ad6     ONLINE       0     0     0

errors: No known data errors


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## Rbby258

can you make drive pools with freenas like on flexraid if not is there somthing else that will let me use different sized hard drives to create a single drive and runs without a OS?


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## Plan9

Quote:


> Originally Posted by *Rbby258*
> 
> can you make drive pools with freenas like on flexraid if not is there somthing else that will let me use different sized hard drives to create a single drive and runs without a OS?


ZFS does support having pools that can exist of single disks, mirrors and multi-disk raids. with the raids, the disks should be the same size (you can mix and match different sized disks in a raid, but it's fiddly and I wouldn't recommend it). The problem with adding single disks to the pool is you don't have any redundancy.

What I do with ZFS is buy 3 disks at a time and grow my pool with a 3x HDD RAID (raidz1, being the technical term).


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## Rbby258

Quote:


> Originally Posted by *Plan9*
> 
> ZFS does support having pools that can exist of single disks, mirrors and multi-disk raids. with the raids, the disks should be the same size (you can mix and match different sized disks in a raid, but it's fiddly and I wouldn't recommend it). The problem with adding single disks to the pool is you don't have any redundancy.
> What I do with ZFS is buy 3 disks at a time and grow my pool with a 3x HDD RAID (raidz1, being the technical term).


i just have alot of random size hard drives from 80gb-2TB i didnt really want to buy 2TB hard drives although if i could i would but at £100+ per drive not now.


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## reezin14

Quote:


> Originally Posted by *Plan9*
> 
> You don't need as much as 6GB of RAM, 4GB would easily be enough. But when RAM is cheap, there's no harm in going over.


4GB might be enough to run ZFS but how well will it perform?


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## Pip Boy

you could try Nas4free ? its an official continuation of freenas 7 which is considered much less resource hungry than 8

http://www.nas4free.org/


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## dushan24

Memory requirements increase as a function of increasing storage size (assuming RAIDz etc.)

Follow what they say on their website, it seems to be spot on.

I have 8GB of RAM in mine...


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## Plan9

Quote:


> Originally Posted by *reezin14*
> 
> 4GB might be enough to run ZFS but how well will it perform?


It would perform fine. You only need 2GB for pre-fetch to work, then you have the memory requirements for the file system itself which are ~1GB per pool (i think, or maybe xTB - but the memory requirements is somewhere in that region for home servers anyway) and then the OS foot print which wouldn't be much at all (particularly for FreeNAS). So yeah, ZFS should run fine on 4GB RAM on an average home server.

However, I'm not arguing that he shouldn't buy 8GB RAM (RAM is cheap so there's really no reason not to buy 8GB), I'm just stating you don't _need_ 8GB to run ZFS. I think because RAM so cheap these days, some people forget just how well UNIX performs on comparatively low end hardware (though I appreciate this discussion is about ZFS rather than UNIX)

[edit]

That image is wrong (or FreeNAS has done some screwy stuff to FreeBSD's ZFS driver) because FreeBSD specifically warned me that I need 2GB of usable RAM to enable pre-fetching (back when I was running 5 Linux virtual machines and ZFS (3x 1TB raidz1) on a 4GB FreeBSD 8.1 box). Whether v28 requires double the RAM or not I don't know (I can't find any reference that suggests it does) but FreeBSD's only tuning guide talks about significantly less memory requirements that you suggest: http://wiki.freebsd.org/ZFSTuningGuide

The only explanation I can think of is FreeNAS has deduping enabled by default - which _is_ very memory hungry. But it also adversely affects performance too. So if performance is an issue then you would prefer to have less RAM and no deduping than more RAM with deduping.

So all in all, I can't really work out where those figures in your link came from.


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## reezin14

Quote:


> Originally Posted by *Plan9*
> 
> It would perform fine. You only need 2GB for pre-fetch to work, then you have the memory requirements for the file system itself which are ~1GB per pool (i think, or maybe xTB - but the memory requirements is somewhere in that region for home servers anyway) and then the OS foot print which wouldn't be much at all (particularly for FreeNAS). So yeah, ZFS should run fine on 4GB RAM on an average home server.
> However, I'm not arguing that he shouldn't buy 8GB RAM (RAM is cheap so there's really no reason not to buy 8GB), I'm just stating you don't _need_ 8GB to run ZFS. I think because RAM so cheap these days, some people forget just how well UNIX performs on comparatively low end hardware (though I appreciate this discussion is about ZFS rather than UNIX)
> [edit]
> That image is wrong (or FreeNAS has done some screwy stuff to FreeBSD's ZFS driver) because FreeBSD specifically warned me that I need 2GB of usable RAM to enable pre-fetching (back when I was running 5 Linux virtual machines and ZFS (3x 1TB raidz1) on a 4GB FreeBSD 8.1 box). Whether v28 requires double the RAM or not I don't know (I can't find any reference that suggests it does) but FreeBSD's only tuning guide talks about significantly less memory requirements that you suggest: http://wiki.freebsd.org/ZFSTuningGuide
> The only explanation I can think of is FreeNAS has deduping enabled by default - which _is_ very memory hungry. But it also adversely affects performance too. So if performance is an issue then you would prefer to have less RAM and no deduping than more RAM with deduping.
> So all in all, I can't really work out where those figures in your link came from.


Interesting stuff,I myself forget how efficient FreeBSD/UNIX is.The image comes straight from the FreeNas site,but like you stated maybe the FreeNas developers have made changes in someway? As we know FreeNas is a derivative of FreeBSD so.


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