Migrating from SinglePath to MultiPath SAS?

[MrAkai]

Hello!

I'm currently running FreeNAS 9.2.1.9 on SuperMicro a server with 2 SAS shelves.

Due to where they are in the rack, each shelf has a single SAS connection back to the head unit.

We are re-racking the system and will be capable of re-running the SAS cabling in a multipath arrangement (2 connections to each shelf).

Is there a way to (either auto-magically or manually) to convert the singlepath setup to multipath without loosing the data? Since gmultipath writes (or can write) metadata to the drives, I want to make sure it won't accidentally overwrite something needed to import the pool on boot.

Thanks!

 

[mav@]

gmultipath stores its metadata in the last sector of the disk. FreeNAS will probably do it as soon as second path is detected. Unfortunately the same last sector is used by backup GPT partition table. GPT should survive without backup table, but I am not sure about its reaction on decreasing of the underlying disk size by one sector due to gmultipath.