The Hadoop Distributed File System (HDFS) is designed to run on top of an underlying filesystem in an operating system. Cloudera recommends that you use either of the following filesystems tested on the supported operating systems:

• ext3: This is the most tested underlying filesystem for HDFS.
• ext4: This scalable extension of ext3 is supported in more recent Linux releases.
    Important: Cloudera does not support in-place upgrades from ext3 to ext4. Cloudera recommends that you format disks as ext4 before using them as data directories.
• XFS: This is the default filesystem in RHEL 7.

Linux filesystems keep metadata that record when each file was accessed. This means that even reads result in a write to the disk. To speed up file reads, Cloudera recommends that you disable this option, called atime, using the mount option in /etc/fstab:

/dev/sdb1 /data1 ext4 defaults,noatime 0

Apply the change without rebooting:

mount -o remount /data1