[ale] ZFS on Linux

[Derek Atkins]

Jim,

Jim Kinney <jim.kinney at gmail.com> writes:

> After much research, I have decided to NOT implement ZFS. The main factors of
> interest were the raidz2 and data deduplication. In order to support the
> deduplication,the server needs 5G RAM per 1TB storage. That's a deal breaker
> right there as the system to be used will only support 32G and has 50TB.
> Raidz2 is basically software RAID6 which I can already do.
>
> Looked at getting an SSD for the deduplication data and using l2arc but I have
> no space to install it on that server. Grr.

Do you really feel you need ZFS deduplication?  According to
http://doc.freenas.org/index.php/Hardware_Recommendations you only need
5GB/TB if you're using dedup.  If you're just using ZFS then they
recommend 1GB/TB.  Granted, if you've got 50TB of data then a 32GB
memory limit wont be useful to you.

However, thank you for making me look at that; I was considering a
32GB-limit Mobo for my system, which I was expecting to start at 12TB
usable but potentially expanding to 96TB.  I don't think a 96TB ZFS
would work well with 32GB memory.

OTOH, is ZFS really only just "RAID6"?  I thought that the ZFS checksums
would provide improved data integrity (scrubbing) over pure RAID6?

-derek

> On Fri, Mar 29, 2013 at 3:10 PM, Ed Cashin <ecashin at noserose.net> wrote:
>
>     Thanks in advance for the notes you take.  I'm interested to hear what you
>     find.
>    
>     By the way, work sent me to a Nexenta course in 2010 where I learned ZFS
>     stuff from Richard Elling:
>    
>       http://www.richardelling.com/
>    
>     ... and one thing that kept coming up is how users usually reach for the
>     RAID-Z options when stripes of mirrors would perform better and offer more
>     flexibility.  I thought that was notable.
>
>     On Fri, Mar 29, 2013 at 2:44 PM, Jim Kinney <jim.kinney at gmail.com> wrote:
>    
>         There was an update to this that just hit /.
>        
>         WooHoo!
>        
>         I have not used ZFS (minimal solaris experience) before but I have a
>         situation where raidz looks like a very good choice. An external 16
>         bay JBOD box hanging off a SAS HBA looks like a prime candidate. The
>         big issue for me is the support for native NFSv4 ACLs which solves
>         some issues.
>        
>         As I go through this exercise, I'll keep some notes and maybe look at
>         a presentation on doing this.
>        
>         hints, gotcha's, are very welcome.
>        
>         I did find a pdf of the zfsadmin.pdf  http://pdfhome.org/zfsadmin.pdf
>        
>         --
>         --
>         James P. Kinney III
>        
>         Every time you stop a school, you will have to build a jail. What you
>         gain at one end you lose at the other. It's like feeding a dog on his
>         own tail. It won't fatten the dog.
>         - Speech 11/23/1900 Mark Twain
>        
>         http://electjimkinney.org
>         http://heretothereideas.blogspot.com/
>        
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>     --
>       Ed Cashin <ecashin at noserose.net>
>       http://noserose.net/e/
>       http://www.coraid.com/
>    
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> --
> --
> James P. Kinney III
>
> Every time you stop a school, you will have to build a jail. What you gain at
> one end you lose at the other. It's like feeding a dog on his own tail. It
> won't fatten the dog.
> - Speech 11/23/1900 Mark Twain
>
> http://electjimkinney.org
> http://heretothereideas.blogspot.com/
>
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-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/    PP-ASEL-IA     N1NWH
       warlord at MIT.EDU                        PGP key available