Todd Sawyers wrote:> I am planning to use zfs with fiber attached san disk from a emc
symmetrix''s
> Based on a note in the admin guide it appears that even though
> the symmetrixs will handle the hardware raid it is still advisable to
create
> a zfs mirror on the host side to take full advantage of zfs''s self
> healing/error checking and correcting.
>
> is this true ?
Yes, though you have more options than just mirroring. Consider setting
policies on important file systems such as copies=2.
> Additionally I am wondering how the zfs mirror will handle a backend
> disk failure on the Symmetrixs ?
> with vxvm disk failures are transparent and nothing needs to be done on
> the host side.
As long as the Symmetrix does not propagate the error to the host, then
it should work the same. However, rather than just trust the storage,
ZFS will verify the data with checksums. This is a good thing.
> Will this be the same with zfs ? or will zpool replace commands need to
> be run ?
As long as the data at the host is good, no ZFS commands are needed.
However, there have been occasional reports of failed SAN hardware
corrupting data. ZFS can detect this, and given enough redundancy, can
correct the data.
-- richard