Jason J. W. Williams wrote:
Hi Richard,
Originally, my thinking was I'd like drop one member out of a 3 member
RAID-Z and turn it into a RAID-1 zpool.
You would need to destroy the pool to do this -- requiring the data to
be copied twice.
Although, at the moment I'm not sure.
So many options, so little time... :-)
Currently, I have 3 volume groups in my array with 4 disk each (total
12 disks). These VGs are sliced into 3 volumes each. I then have two
database servers using one LUN from each of the 3 VGs RAID-Z'd
together. For redundancy its great, for performance its pretty bad.
One of the major issues is the disk seek contention between the
servers since they're all using the same disks, and RAID-Z tries to
utilize all the devices it has access to on every write.
This is difficult to pin down. The disks cache and the RAID controller
caches. So it is true that you would have contention, it is difficult
to predict what affect, if any, the hosts would see.
What I thought I'd move to was 6 RAID-1 VGs on the array, and assign
the VGs to each server via a 1 device striped zpool. However, given
the fact that ZFS will kernel panic in the event of bad data I'm
reconsidering how to lay it out.
NB. all other file systems will similarly panic. We get spoiled to
some extent because there are errors where ZFS won't panic. In the
future, there will be more errors that ZFS can handle without panic.
Essentially I've got 12 disks to work with.
Anyway, long form of trying to convert from RAID-Z to RAID-1. Any help
is much appreciated.
send/receive = copy/copy = backup/restore
It may be possible to do this as a rolling reconfiguration.
-- richard
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