Advice. Change a RAID1 setup to RAID0 (I need the extra space)

I have a hosted server (unmanaged) running MySQL with the following setup:

Filesystem Size Used Avail Use% Mounted on /dev/sda6 457G 175G 260G 41% / /dev/sda1 92M 33M 55M 38% /boot /dev/md1 917G 760G 158G 83% /u01 

the data files of our MySQL are on /u01, which is configured as RAID1:

/dev/md1: Version : 1.2 Creation Time : Wed Jun 8 14:25:05 2011 Raid Level : raid1 Array Size : 976758841 (931.51 GiB 1000.20 GB) Used Dev Size : 976758841 (931.51 GiB 1000.20 GB) Raid Devices : 2 Total Devices : 2 Persistence : Superblock is persistent Update Time : Fri Jul 13 15:46:01 2012 State : clean Active Devices : 2 Working Devices : 2 Failed Devices : 0 Spare Devices : 0 Name : xxxxx:1 (local to host xxxxx) UUID : dfc23c73:bbaf88af:7b664d80:ff116079 Events : 476 Number Major Minor RaidDevice State 0 8 17 0 active sync /dev/sdb1 1 8 33 1 active sync /dev/sdc1 

As you can see, i'm running out of space, and i'm going to need it, we're growing the database at a rate of about 20 GB a DAY ! I'm allowed to clean up and move to backup media records older than 2 months, problem is, the current setup can only hold 1.5 months of data.

so, what can i do ?

option 1: create a /dev/md2 and concatenate a 2 TB drive at the end of md1. the new disk wouldn't be mirrored (the server accepts a maximum of 4 HDs). option 2: split /dev/md1, convert it from RAID1 to RAID0 and concatenate one of the disks at the end.

dificulty level: minimum downtime.

so, which one can be done more easily, with lower dowtime and less risk of data loss ? assuming full backup/wipe/restore is impossible ?

Edit: fixed the screen grabs