When is ext5 coming or when will ext4 be updated to support large (huge) SSDs?

Question

There is already the Nimbus ExaDrive 100TB SSD and the 200TB SSD will come soon. As you can read here ext4 supports up to 256 TB. It's only a matter of time hardware will reach this limit.

Will they update ext4 or will there be ext5? What will happen?

Answer 1

64-bit ext4 file systems can be up to 64ZiB in size with 4KiB blocks, and up to 1YiB in size with 64KiB blocks, no need for an ext5 to handle large volumes. 1 YiB, one yobibyte, is 1024⁸ bytes.

There are practical limits around 1 PiB and 1 EiB, but that’s still (slightly) larger than current SSDs, and the limits should be addressable within ext4, without requiring an ext5.

Answer 2

The 64bit ext4 filesystem feature removes the 2³² block limit. If this feature was not enabled when your filesystem was created, you can add it to the superblock using tune2fs(8):

tune2fs -O 64bit /dev/sda1

This is a filesystem feature, not a mount option, so it must be specified either while creating the filesystem, or added later. From ext4(5):

  64bit
         Enables the file system to be larger than 2^32 blocks.
         This feature is set automatically, as needed, but it can
         be useful to specify this feature explicitly if the file
         system might need to be resized larger than 2^32 blocks,
         even if it was smaller than that threshold when it was
         originally created.  Note that some older kernels and
         older versions of e2fsprogs will not support file systems
         with this ext4 feature enabled.

Any ext4 filesystem built with mke2fs since 2015 will have this feature enabled by default.

Answer 3

While ext4 can in theory handle filesystems up to 2^64 * blocksize = 64ZiB in size (for commonly used 4KiB blocksize), on a more practical note there are implementation contstraints today at 2^48 * blocksize = 1EiB (@ 4KiB blocksize) due to the inode's 2^48-1 block address limit for the extent format currently in use. There start to be some performance issues above 1 PiB due to the current block allocator, though still pretty usable and we have many hundreds of ext4 filesystems around this size in production. The block allocator can probably be fixed in the code without any (major) on-disk format changes, and the extent format could also be extended once it becomes a real limitation.

Answer 4

Others have answered the question about large partitions, but I thought it would be helpful to answer the question about when ext5 is coming.

Ext4 is currently maintained by Theodore Ts'o. According to a 2009 Ars Technica article:

Despite the fact that Ext4 adds a number of compelling features to the filesystem, T'so doesn't see it as a major step forward. He dismisses it as a rehash of outdated "1970s technology" and describes it as a conservative short-term solution. He believes that the way forward is Oracle's open source Btrfs filesystem, which is designed to deliver significant improvements in scalability, reliability, and ease of management.

Of course this is far from a firm commitment to never implement a file system called ext5, but I believe there is little appetite for this right now.