lv mirror on 2 campus

[Steve White_7]

Hi,

You might want to be careful if that system is rebooted. Volume Groups require what is known as quorum to activate. You system may be configured to actviate without quorum, if not you will have to manually run vgchange in order to mount the filesystems in that volume group. The vgsync binary can be run once you get the other storage back on-line.

Cheers

[Bill Hassell]

LVM mirroring was never designed for long distance mirroring. Unless your long distance connection is 100% fibre, you will find normal operations slower than supported configurations (local disks). In simple terms, once a mirror is not functioning, LVM will mark the extents on the disabled disk as stale and will not attempt to write anything to them. This is exactly the same as a local mirror.

But that's the simple explanation. Many failures are much more complicated and highly intelligent I/O cards (such as fibre), special fibre switches (such as Brocade) and the arrays themselves can fail in strange ways, causing long delays as the driver attempts to recover from the problem. A solid failure (complete disconnect) will probably work as expected but electronic failures may cause excessive delays in the driver. The long distance between the two disks isn't helping at all.

You have to ensure that the remote disk and communication path never go down. I would not recommend running a production server in this manner due to all sorts of timing and error recovery problems. There are special disk arrays that are specifically designed for long distance redundancy.