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[ale] ZFS on Linux
- Subject: [ale] ZFS on Linux
- From: warlord at MIT.EDU (Derek Atkins)
- Date: Mon, 22 Apr 2013 13:24:44 -0400
- In-reply-to: <CAEo=5Py-0YUurOz7E3JBDYrVqw3DQs4UQ3H6UdBMYVRMqO=t3g@mail.gmail.com> (Jim Kinney's message of "Fri, 19 Apr 2013 12:28:33 -0400")
- References: <CAEo=5Pw=3XiVtN6HdJgKO+-m4=GVmDGkENrxa3SD-Bgy6Rbnpg@mail.gmail.com> <CADvA-dmb+RR3XmYgDbRZvKEyU6cNx66A2fRD3C5NYx2kOogJtw@mail.gmail.com> <CAEo=5Pw6bDfAKE-YMnQodmcdouAH9xvv=vNZTCPdkw-5=2JdnA@mail.gmail.com> <[email protected]> <CAEo=5Py-0YUurOz7E3JBDYrVqw3DQs4UQ3H6UdBMYVRMqO=t3g@mail.gmail.com>
Jim Kinney <jim.kinney at gmail.com> writes:
> given what the drive arrays are used for, dedup is a big plus (people make
> copies and copies of research files like drive space is $0!). And, yeah, even
> with no dedup, 32G is not going to cut it anyway.
You can get mobos that support 256MB for not too much money.
For my case I cannot imagine that dedup would significantly help me; my
plan is to store audio and video, and perhaps *some* VM data, but most
likely I don't imagine that dedup would do *me* any signigicant
advantage.
> The checksums for RAID6 are the same as in raidz2.
Are they? I though ZFS/RAID-Z(2) had additional checksums above and
beyond what RAID5(6) provided, such that it could detect and correct a
write-hole (or other) disk/storage failure.
> I found a 250G SSD but can't use it. I have one other system I can put it on
> but it has not enough PCIe slots for the need.
>
> the solution to all of this is $$$$$ for new system :-(
Or just replace the mobo ;)
-derek
> On Fri, Apr 19, 2013 at 11:58 AM, Derek Atkins <warlord at mit.edu> wrote:
>
> 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/
> >
> > ? ? ? ? _______________________________________________
> > ? ? ? ? Ale mailing list
> > ? ? ? ? Ale at ale.org
> > ? ? ? ? http://mail.ale.org/mailman/listinfo/ale
> > ? ? ? ? See JOBS, ANNOUNCE and SCHOOLS lists at
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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/
> >
> > _______________________________________________
> > Ale mailing list
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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
>
> _______________________________________________
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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/
>
> _______________________________________________
> Ale mailing list
> Ale at ale.org
> http://mail.ale.org/mailman/listinfo/ale
> See JOBS, ANNOUNCE and SCHOOLS lists at
> http://mail.ale.org/mailman/listinfo
--
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