Especially, which among the newest ext4 and btrfs are fully supported as boot partition by GRUB Legacy and which by GRUB 2?
Lisandro Damián Nicanor Pérez Meyer
[ Editor ]
According to GNU GRUB Manual 1.99~beta0: “Amiga Fast FileSystem (AFFS), AtheOS fs, BeFS, cpio, Linux ext2/ext3/ext4, DOS FAT12/FAT16/FAT32, HFS, HFS+, ISO9660, JFS, Minix fs, nilfs2, NTFS, ReiserFS, Amiga Smart FileSystem (SFS), tar, UDF, BSD UFS/UFS2, and XFS.” That will count for GRUB 2.
To see wich filesystems GRUB legacy supports, check it’s manual.