During first startup, you may see the error message:
File system on /var/lib/scylla is not qualified for seastar AIO
There can be two causes for this error:
You are not using XFS on your data directory
Remedy: format the data directory with XFS
You are using XFS, but the kernel version is too old; see below for affected kernels
Remedy: upgrade your kernel
Scylla requires using the XFS filesystem, since it is the only Linux filesystem with good Asynchronous I/O support. In addition, Linux kernels before 3.15 did not have good asynchronous append support, which is required by Scylla.
If you are using Red Hat Enterprise Linux or CentOS, use version 7.2 or higher of the operating system. These versions contain a kernel that provides the necessary support.
If you are using Ubuntu 14.04, install kernel package
linux-image-generic-lts-vivid. This package contains a kernel that provides the necessary support