ZFS - moving from a zraid1 to zraid2 pool with 1.5tb disks

Matthew Seaman m.seaman at infracaninophile.co.uk
Sun Jan 9 12:06:23 UTC 2011

On 09/01/2011 10:14, Patrick M. Hausen wrote:

> I assume you are familiar with these papers?
> http://queue.acm.org/detail.cfm?id=1317403
> http://queue.acm.org/detail.cfm?id=1670144
> Short version: as hard disk sizes increase to 2 TB and beyond while the URE rate
> stays in the order of 1 to 10^14 blocks read, the probability of encountering an URE
> during rebuild of a single parity RAID approaches 1.

Yes.  Rotating magnetic media seems to be bumping up against some
intrinsic performance/reliability limits to the year-on-year doubling of
capacity.  Having to add more and more "extra" drives to ensure the same
level of reliability is not a wining proposition in the long term.

Roll on solid state storage.  I particularly like the sound of HP and
Hynix's memristor technology. If memristors pan out, then they are going
to replace both D-RAM and hard drives, and eventually replace
transistors as the basic building block for electronic logic circuits.
Five to ten years from now, hardware design is going to be very
different, and the software that runs on it will have to be radically
redesigned to match.  Think what that means.

   * You don't have to *save* a file, ever.  If it's in memory, it's in
     persistent storage.
   * The effect on RDBMS performance is going to be awesome -- none of
     that time consuming waiting for sync-to-disk.
   * A computer should be able to survive a power outage of a few
     seconds and carry on where it left off, without specially going
     into hibernation mode.
   * Similarly, "reboot" will be at the flick of a switch -- pretty
     much instant on.
   * Portables will look a lot more like iPads or other tablet devices,
     and will have battery lifetimes of several days.  About the only
     significant difference is one will have a hinge down the middle
     and a built-in keyboard, while the other will only have the touch

Oh, and let's not forget the beneficial effects of *no moving parts* and
*lower power consumption* on system reliability.  Now all we need are
the telcos to lay multi-Gb/s capacity fibre to every house and business,
and things will start to get very interesting indeed.



Dr Matthew J Seaman MA, D.Phil.                   7 Priory Courtyard
                                                  Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey     Ramsgate
JID: matthew at infracaninophile.co.uk               Kent, CT11 9PW

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