Code:
$ cat test.txt
/dev/rmt/tsmmt32 HP Ultrium 6-SCSI J3LZ 50:03:08:c0:02:72:c0:b5 F00272C0B5 0/0/6/1/1.145.17.255.0.0.0 /dev/rmt/c102t0d0BEST
/dev/rmt/tsmmt37 HP Ultrium 6-SCSI J3LZ 50:03:08:c0:02:72:c0:97 F00272C097 0/0/6/1/1.145.17.255.4.0.0 /dev/rmt/c103t0d0BEST
/dev/rmt/tsmmt48 IBM ULT3580-TD3 5AT0 5458623002 0/0/6/1/1.145.0.255.8.0.0 /dev/rmt/c72t0d0BESTn
/dev/rmt/tsmmt53 IBM ULT3580-TD3 5AT0 5458623006 0/0/6/1/1.145.0.255.8.0.1 /dev/rmt/c72t0d1BESTn
$ expand test.txt | sed 's/ */,/g'
/dev/rmt/tsmmt32,HP,Ultrium 6-SCSI,J3LZ,50:03:08:c0:02:72:c0:b5,F00272C0B5,0/0/6/1/1.145.17.255.0.0.0,/dev/rmt/c102t0d0BEST
/dev/rmt/tsmmt37,HP,Ultrium 6-SCSI,J3LZ,50:03:08:c0:02:72:c0:97,F00272C097,0/0/6/1/1.145.17.255.4.0.0,/dev/rmt/c103t0d0BEST
/dev/rmt/tsmmt48,IBM,ULT3580-TD3,5AT0,5458623002,0/0/6/1/1.145.0.255.8.0.0,/dev/rmt/c72t0d0BESTn
/dev/rmt/tsmmt53,IBM,ULT3580-TD3,5AT0,5458623006,0/0/6/1/1.145.0.255.8.0.1,/dev/rmt/c72t0d1BESTn
$ sed -e 's/\t/,/g' -e 's/ */,/g' test.txt
/dev/rmt/tsmmt32,HP,Ultrium 6-SCSI,J3LZ,50:03:08:c0:02:72:c0:b5,F00272C0B5,0/0/6/1/1.145.17.255.0.0.0,/dev/rmt/c102t0d0BEST
/dev/rmt/tsmmt37,HP,Ultrium 6-SCSI,J3LZ,50:03:08:c0:02:72:c0:97,F00272C097,0/0/6/1/1.145.17.255.4.0.0,/dev/rmt/c103t0d0BEST
/dev/rmt/tsmmt48,IBM,ULT3580-TD3,5AT0,5458623002,0/0/6/1/1.145.0.255.8.0.0,/dev/rmt/c72t0d0BESTn
/dev/rmt/tsmmt53,IBM,ULT3580-TD3,5AT0,5458623006,0/0/6/1/1.145.0.255.8.0.1,/dev/rmt/c72t0d1BESTn
$