Gary Mills wrote:
On Wed, Jun 20, 2007 at 12:23:18PM -0400, Torrey McMahon wrote:
James C. McPherson wrote:
Roshan Perera wrote:
But Roshan, if your pool is not replicated from ZFS' point of view,
then all the multipathing and raid controller backup in the world will
not make a difference.
James, I Agree from ZFS point of view. However, from the EMC or the
customer point of view they want to do the replication at the EMC level
and not from ZFS. By replicating at the ZFS level they will loose some
storage and its doubling the replication. Its just customer use to
working with Veritas and UFS and they don't want to change their
habbits.
I just have to convince the customer to use ZFS replication.
that's a great shame because if they actually want
to make use of the features of ZFS such as replication,
then they need to be serious about configuring their
storage to play in the ZFS world.... and that means
replication that ZFS knows about.
Also, how does replication at the ZFS level use more storage - I'm
assuming raw block - then at the array level?
SAN storage generally doesn't work that way. They use some magical
redundancy scheme, which may be RAID-5 or WAFL, from which the Storage
Administrator carves out virtual disks. These are best viewed as an
array of blocks. All disk administration, such as replacing failed
disks, takes place on the storage device without affecting the virtual
disks. There's no need for disk administration or additional
redundancy on the client side. If more space is needed on the client,
the Storage Administrator simply expands the virtual disk by extending
its blocks. ZFS needs to play nicely in this environment because
that's what's available in large organizations that have centralized
their storage. Asking for raw disks doesn't work.
Are we talking about replication - I have a copy of my data on an other
system - or redundancy - I have a system where I can tolerate a local
failure?
...and I understand the ZFS has to play nice with HW raid argument. :)
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