etx4: failed to create a filesystem with block size less than 4 KB on large partition

Question

OS: Ubuntu 18.04 File system partition size: 472 TB

ext4 file system is successfully created with 4KB block size.

When attempted to create same filesystem with 1KB or 2KB file system block szie getting below error:

mke2fs 1.44.1 (24-Mar-2018)
Warning: specified blocksize 1024 is less than device physical sectorsize 4096
mkfs.ext4: Size of device (0x763cd7f000 blocks) /dev/md127 too big to create a filesystem using a blocksize of 1024.

Is there any way to fix this? I need to run performance experiment with varying the ext4 file system block size.

Answer 1

It work if you use a newer mke2fs:

% mke2fs -t ext4 -b 1024 /tmp/foo.img 472T
mke2fs 1.45.5 (07-Jan-2020)
Creating regular file /tmp/foo.img
Creating filesystem with 506806140928 1k blocks and 3959422976 inodes
Filesystem UUID: 64d8234d-68d8-42a8-9dba-414523184256
Superblock backups stored on blocks: 
    8193, 24577, 40961, 57345, 73729, 204801, 221185, 401409, 663553, 
    1024001, 1990657, 2809857, 5120001, 5971969, 17915905, 19668993, 
    25600001, 53747713, 128000001, 137682945, 161243137, 483729409, 
    640000001, 963780609, 1451188225, 3200000001, 4353564673, 6746464257, 
    13060694017, 16000000001, 39182082049, 47225249793, 80000000001, 
    117546246145, 330576748545, 352638738433, 400000000001

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (262144 blocks): done
Writing superblocks and filesystem accounting information: Done

You can probably make it work by adding -O 64bit to the mke2fs command, but there have been a huge number of bug fixes since the 1.44.x series, so my recommendation is updating to something more up-to-date. In particular, if you want to use online resize, especially with 64-bit file systems, DO NOT use the version of resize2fs with Ubuntu LTS. You really really REALLY want e2fsprogs 1.45.5. See the "bug fixes" section in the release notes.

Answer 2

IIRC, most filesystems only support a limited number of blocks per file system.

That is, if you pick a block size that is too low, the size of the partition (measured in blocks) gets too big to create the filesystem.

A partition of 472 TiB equals 501856862208 blocks if you use 1K-Blocks and my guess is that this exceeds the limit. If, however, you use blocks of 4096 B, then your file system would only be 125464215552 blocks in size which apparantly still works.

If you really need a file system with 1K blocks, you will have to divide your disk into several smaller partitions.

Alternatively, if you don't mind wasting disk space, you could create a file system that uses only part of the partition. I. e. there would be a filesystem at the beginning of the partition and the rest of the partition would be unused.