Chapter 9. File Systems

Distributed File System (DFS), which was previously supported only with the Server Message Block (SMB) protocol version 1, is now also supported in SMB 2 and SMB 3.

With this update, you can now mount DFS shares using the SMB 2 and SMB 3 protocols. (BZ#1481303)

Prior to this enhancement, the Direct Access (DAX) feature mapped only 4KiB entries into application address space. This had a negative performance impact on workloads that mapped large amounts of memory, because it increased Translation Lookaside Buffer (TLB) pressure. With this update, the kernel supports 2MiB Page Middle Directory (PMD) faults in persistent memory mappings. This significantly reduces TLB pressure, and file system DAX now performs better when mapping a large amount of memory. (BZ#1457572)

The quotacheck utility now directly scans ext4 file system metadata instead of analyzing each individual file for occupied disk size. If the file system contains many files, quota initialization and quota check are now significantly faster. (BZ#1393849)

The Ceph File System (CephFS) kernel module enables Red Hat Enterprise Linux nodes to mount Ceph File Systems from Red Hat Ceph Storage clusters. The kernel client in Red Hat Enterprise Linux is a more efficient alternative to the Filesystem in Userspace (FUSE) client included with Red Hat Ceph Storage. Note that the kernel client currently lacks support for CephFS quotas.

The CephFS kernel client was introduced in Red Hat Enterprise Linux 7.3 as a Technology Preview, and since the release of Red Hat Ceph Storage 3, CephFS is fully supported.

For more information, see the Ceph File System Guide for Red Hat Ceph Storage 3: https://access.redhat.com/documentation/en-us/red_hat_ceph_storage/3/html/ceph_file_system_guide/. (BZ#1626526)