ZFS RaidZ2 with 24 drives?

[Thomas Burgess]

On Fri, Dec 18, 2009 at 10:28 AM, James R. Van Artsdalen <
james-freebsd-fs2 at jrv.org> wrote:

> Thomas Burgess wrote:
> > One thing most people don't know about hard drives in general is that
> > sometimes up to 30% of the space is actually ECC.  With software raid
> > systems like ZFS, this will eventually be somethign that we can take
> > advantage of.
>
> i was basing this information on a talk Jeff Bonwick gave.  Google
JeffBonwick_*zfs*-What_*Next*-SDC09.pdfand it should show the information
i'm talking about.


> ECC is less than 10% of the space.  The inter-sector gap and gap between
> a sector's address and data fields, etc, are larger and more problematic
> as rotation speeds increase.
>
> > Because of this,  you can imagine a scenario where  allowing ZFS to
> > use this ECC space as raw storage, while leaving the data corrections
> > to ZFS would be ideal.  It's not only a matter of space, it will also
> > lead to nice improvements in speed.  (more data can be read/written by
> > the head as it passes)
>
> The disk drive industry's solution to this is 4K sector sizes.  See
> http://www.anandtech.com/storage/showdoc.aspx?i=3691
>
> Even ZFS would need major changes to use drives without ECC without an
> increased hard error rate.  I don't see this happening since no
> filesystems exist yet for this environment, and since transitions to new
> filesystems are so slow (99.9%+ of systems today are running filesystems
> architectures at least two decades old).
>

again, i got my information from the lead zfs developer. I also spent a lot
of time on google reading up on this after hearing about it because i found
it to be so interesting.  I am a layman though, so perhaps i'm wrong.