What's the best file system for Ubuntu 10.10 assuming the average filesize is 8-30GB with no more than 1-2 users accessing the array at any given time?
Of the two you've listed (ext3 and XFS) I'd be tempted to go with XFS, both have broadly similar capabilities and you don't sound like you'll be pushing them particularly hard but given ext3 can only really grow to 32TB maximum and you already want 20TB on day one I'd say go with XFS simply because it'll allow for larger and smoother growth if you ever go past this 32TB limit.
Given that ext3 and ext4 are still limited to 16TB volumes (a limit of 2^32 4KiB blocks for ext2/3, and while ext4 has a higher limit in theory e2fsprogs doesn't support it), I'd say that your only real option for a widely used, stable filesystem is XFS.
EDIT: Adding note around why ext3 will not work at all, even if you change the blocksize.
$ head -n2 /etc/motd Linux uranium 2.6.35-24-generic #42-Ubuntu SMP Thu Dec 2 02:41:37 UTC 2010 x86_64 GNU/Linux Ubuntu 10.10 $ mkfs.ext3 -b 8192 ./8KiBfs Warning: blocksize 8192 not usable on most systems. mke2fs 1.41.12 (17-May-2010) mkfs.ext3: 8192-byte blocks too big for system (max 4096) Proceed anyway? (y,n) y Warning: 8192-byte blocks too big for system (max 4096), forced to continue ./8KiBfs is not a block special device. Proceed anyway? (y,n) y Filesystem label= OS type: Linux Block size=8192 (log=3) Fragment size=8192 (log=3) Stride=0 blocks, Stripe width=0 blocks 16384 inodes, 16384 blocks 819 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=33550336 1 block group 65528 blocks per group, 65528 fragments per group 16384 inodes per group Writing inode tables: done Creating journal (1024 blocks): done Writing superblocks and filesystem accounting information: done This filesystem will be automatically checked every 25 mounts or 180 days, whichever comes first. Use tune2fs -c or -i to override. $ sudo mount ./8KiBfs /mnt/8KiBfs/ -o loop mount: wrong fs type, bad option, bad superblock on /dev/loop0, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so $ dmesg | tail -n 1 [1396759.041587] EXT3-fs (loop0): error: bad blocksize 8192
I'm not trying to flog a dead horse here, but the people insisting that ext3 will let you build a 32TiB fs using 8KiB blocks have clearly never tried it. I'm open to suggestions about how to make it work, but on the face of it, it just won't work. OK, my test filesystem was only 128MB, but I can't use 8KiB blocks even for that - it's an architecture limitation.
I don't have ready access to a > 16TiB block device to demonstrate the limitations in ext4, but I can probably arrange that next week.
XFS is definitely the best option given what we currently know.
Typically, filesystem performance differs when you have 1) very small files, 2) very many files, or 3) very deep directory trees. Since neither of these criteria apply here, I expect you are not going to see a significant performance difference from filesystem. I would choose ext3 in order to be as mainstream as possible.
I'm using XFS for similar configuration (12 x 2TB in RAID-6) it performs very well, but you can go with EXT4 or JFS. I would not recommend EXT3 though - it is outdated and it is rather inefficient on multi-core systems and when deleting many files. In either case, make sure your FS is aligned with dimensions of your RAID array (i.e. stripe size and stripe width). Here is my reply in another thread with sample configuration for XFS.
If you are using raid 5 you may want to use raid 5 +0 for big files, this uses blocks instead of bits. so raid 5 is better for smaller files and 5+0 or what is called raid 50 is better for larger files like movies, As far as the file system goes a ext4 or NTFS, Both support very large file systems and i believe ext4 is a 128bit system, will due fine depending on the OS you are using.
The primary reason to use ext4 over ext3 for a file system of that size would be that file deletion in ext4 for large files (of more then a few hundred megabytes) is made significantly faster due to the use of extents in ext4. Deleting a large multi-gigabyte file under ext3 is an exercise in patience as it goes scurrying around to free up the blocks. That can take up to a few minutes for larger files. Deleting the same multi-gigabyte file in ext4 typically only takes a few seconds.