Silo and /boot raid device

[BERTRAND Joël <joel.bertrand@systella.fr>]

	Hello,

	I have installed a long time ago debian/sparc64 on several T1000. /boot 
was a raid1 volume.

	Last week, I have replaced one disk (/dev/sdb) and rebuilt all raid 
volumes :

md5 : active raid1 sda8[0] sdb8[1]
      14538752 blocks [2/2] [UU]

md4 : active raid1 sda7[0] sdb7[1]
      4883648 blocks [2/2] [UU]

md3 : active raid1 sda6[0] sdb6[1]
      9767424 blocks [2/2] [UU]

md2 : active raid1 sda5[0] sdb5[1]
      29294400 blocks [2/2] [UU]

md1 : active raid1 sda2[0] sdb2[1]
      489856 blocks [2/2] [UU]

md6 : active raid1 sda1[0] sdb1[1]
      7815552 blocks [2/2] [UU]

md0 : active raid1 sdb4[1] sda4[0]
      4883648 blocks [2/2] [UU]

	Server boots but I not able to reinstall silo bootblock on /dev/sdb. 
Silo only returns :

Root gershwin:[~] > silo
/etc/silo.conf appears to be valid
Fatal error: File systems other than ext2, ext3, ufs and romfs not yet 
supported
Root gershwin:[~] >

	I don't understand. Of course, /boot fs is ext3 and mdadm --detail 
returns :

Root gershwin:[~] > mdadm --detail /dev/md1
/dev/md1:
        Version : 0.90
  Creation Time : Wed Aug  1 19:40:02 2007
     Raid Level : raid1
     Array Size : 489856 (478.46 MiB 501.61 MB)
  Used Dev Size : 489856 (478.46 MiB 501.61 MB)
   Raid Devices : 2
  Total Devices : 2
Preferred Minor : 1
    Persistence : Superblock is persistent

    Update Time : Sun Aug 31 09:58:55 2014
          State : clean
 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0

           UUID : 187be6f5:c6efc575:b23d8119:3921b2dd
         Events : 0.849

    Number   Major   Minor   RaidDevice State
       0       8        2        0      active sync   /dev/sda2
       1       8       18        1      active sync   /dev/sdb2
Root gershwin:[~] >

	Where is my mistake ?

	Regards,

	JB