UnifyFS Configuration

Here, we explain how users can customize the runtime behavior of UnifyFS. In particular, UnifyFS provides the following ways to configure:

  • System-wide configuration file: /etc/unifyfs/unifyfs.conf
  • Environment variables
  • Command line options to unifyfsd

All configuration settings have corresponding environment variables, but only certain settings have command line options. When defined via multiple methods, the command line options have the highest priority, followed by environment variables, and finally config file options from unifyfs.conf.

The system-wide configuration file is used by default when available. However, users can specify a custom location for the configuration file using the -f command-line option to unifyfsd (see below). There is a sample unifyfs.conf file in the installation directory under etc/unifyfs/. This file is also available in the extras directory in the source repository.

The unified method for providing configuration control is adapted from CONFIGURATOR. Configuration settings are grouped within named sections, and each setting consists of a key-value pair with one of the following types:

  • BOOL: 0|1, y|n, Y|N, yes|no, true|false, on|off
  • FLOAT: scalars convertible to C double, or compatible expression
  • INT: scalars convertible to C long, or compatible expression
  • STRING: quoted character string


unifyfs.conf specifies the system-wide configuration options. The file is written in INI language format, as supported by the inih parser.

The config file has several sections, each with a few key-value settings. In this description, we use section.key as shorthand for the name of a given section and key.

[unifyfs] section - main configuration settings
Key Type Description
cleanup BOOL cleanup storage on server exit (default: off)
configfile STRING path to custom configuration file
consistency STRING consistency model [ LAMINATED | POSIX | NONE ]
daemonize BOOL enable server daemonization (default: off)
mountpoint STRING mountpoint path prefix (default: /unifyfs)
[client] section - client settings
Key Type Description
cwd STRING effective starting current working directory
max_files INT maximum number of open files per client process (default: 128)
local_extents BOOL service reads from local data if possible (default: off)
recv_data_size INT maximum size (B) of memory buffer for receiving data from server
write_index_size INT maximum size (B) of memory buffer for storing write log metadata

The cwd setting is used to emulate the behavior one expects when changing into a working directory before starting a job and then using relative file names within the application. If set, the application changes its working directory to the value specified in cwd when unifyfs_mount is called. The value specified in cwd must be within the directory space of the UnifyFS mount point.

Enabling the local_extents optimization may significantly improve read performance. However, it should not be used by applications in which different processes write to a given byte offset within the file, nor should it be used with applications that truncate files.

[log] section - logging settings
Key Type Description
dir STRING path to directory to contain server log file
file STRING log file base name (rank will be appended)
verbosity INT logging verbosity level [0-5] (default: 0)
[logio] section - log-based write data storage settings
Key Type Description
chunk_size INT data chunk size (B) (default: 4 MiB)
shmem_size INT maximum size (B) of data in shared memory (default: 256 MiB)
spill_size INT maximum size (B) of data in spillover file (default: 1 GiB)
spill_dir STRING path to spillover data directory
[meta] section - MDHIM metadata settings
Key Type Description
db_name STRING metadata database file name
db_path STRING path to directory to contain metadata database
range_size INT metadata range size (B) (default: 1 MiB)
server_ratio INT # of UnifyFS servers per metadata server (default: 1)
[runstate] section - server runstate settings
Key Type Description
dir STRING path to directory to contain server runstate file
[server] section - server settings
Key Type Description
hostfile STRING path to server hostfile
init_timeout INT timeout in seconds to wait for servers to be ready for clients (default: 120)
[sharedfs] section - server shared files settings
Key Type Description
dir STRING path to directory to contain server shared files

Environment Variables

All environment variables take the form UNIFYFS_SECTION_KEY, except for the [unifyfs] section, which uses UNIFYFS_KEY. For example, the setting log.verbosity has a corresponding environment variable named UNIFYFS_LOG_VERBOSITY, while unifyfs.mountpoint corresponds to UNIFYFS_MOUNTPOINT.

Command Line Options

For server command line options, we use getopt_long() format. Thus, all command line options have long and short forms. The long form uses --section-key=value, while the short form -<optchar> value, where the short option character is given in the below table.

Note that for configuration options of type BOOL, the value is optional. When not provided, the true value is assumed. If the short form option is used, the value must immediately follow the option character (e.g., -Cyes).

unifyfsd command line options
LongOpt ShortOpt
–unifyfs-cleanup -C
–unifyfs-configfile -f
–unifyfs-consistency -c
–unifyfs-daemonize -D
–unifyfs-mountpoint -m
–log-verbosity -v
–log-file -l
–log-dir -L
–runstate-dir -R
–server-hostfile -H
–sharedfs-dir -S
–server-init_timeout -t