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mfshdd.cfg(5)		     This is part of MooseFS		   mfshdd.cfg(5)

NAME
     mfshdd.cfg - list of MooseFS storage directories for mfschunkserver

DESCRIPTION
     The  file	mfshdd.cfg  contains  list of directories (mountpoints) used for
     MooseFS storage.

   SYNTAX
     Syntax is:

     [*|<|>|~]PATH [SPACE OPTIONS]

     Lines starting with # character are ignored as comments.

     Path can be prefixed with one or more special characters. These  characters
     work as additional options.

	    *	   means this directory (hard drive) is "marked for removal" and
		   all	data will be replicated to other hard drives, usually on
		   other chunkservers

	    <	   means that all data from this hard drive should be  moved  to
		   other local hard drives

	    >	   means  that	all  data from other local hard drives should be
		   moved to this hard drive

	    ~	   means that significant (more than 10% in less than a  minute)
		   change of total blocks count will not mark this drive as dam-
		   aged (useful for compressed filesystems)

     PATH  is  path to the mounting point of storage directory, usually a single
     hard drive.

     SPACE OPTIONS allow to define limits in used space and alter disk usage re-
     porting. A SPACE OPTION can be:

	    a positive space limit, indicating a space	limit  definition  (i.e.
	    only  this	amount of space on the indicated path should be used for
	    chunk storage)

	    a negative space limit, indicating a reserved space definition (i.e.
	    at least this amount of space should always be left free on the  in-
	    dicated path)

	    an equals '=' sign, optionally followed by a space limit indicator

     Space   limit   can   be	either	 a  defined  amount  of  space	(format:
     [0-9]*(.[0-9]*)?([kMGTPE]|[KMGTPE]i)?B?) or a percent of total device size.

     An equals sign indicates, that a disk is "shared" with another process (ei-
     ther another chunk server process or an unrelated process) and  the  amount
     of  space	used  on the disk is not necessarily indicative of the amount of
     space used by chunks. Additionally, an indicator of a space  limit  can  be
     defined.  Percent	says how many percent of the available disk space should
     be considered as available for the chunkserver. Size says	how  much  exact
     space should be considered available for the chunkserver. If the percent or
     space are negative, then we define the unavailable amount of space instead.

     The presence or absence of SPACE OPTION changes the way chunk server calcu-
     lates available and used space on a given path.

     Let's define 3 base values:
     total_hdd - total device size, as returned by statvfs
     avail_hdd - total available space, as returned by statvfs
     calc_size - used space (sum of chunk's disk usage)

     When  there  is  no SPACE OPTION defined then total and available space are
     reported as follows:

     - reported total = total_hdd
     - reported avail = avail_hdd

     Otherwise available space is calculated using formulas:

     1. With constant reserved space (negative space limit -X)
     - reported avail = total_hdd - X - calc_size (or zero if X  +  calc_size  >
     total_hdd)

     2. With perecent of reserved space (negative space limit -X%)
     -	reported avail = total_hdd - total_hdd*X/100 - calc_size (or zero if to-
     tal_hdd*X/100 + calc_size > total_hdd)

     3. With constant space limit (positive space limit X)
     - reported avail = X - calc_size (or zero if calc_size > X)

     4. With percent space limit (positive space limit X%)
     - reported avail = total_hdd*X/100 - calc_size (or zero if calc_size >  to-
     tal_hdd*X/100)

     5. With shared space indicator (= sign)
     - reported avail = avail_hdd

     6. With shared space indicator and space indicator (=X)
     - reported avail = X (or avail_hdd if avail_hdd < X)

     7. With shared space indicator and percent indicator (=X%)
     - reported avail = avail_hdd*X/100

     8. With shared space indicator and negative space indicator (=-X)
     - reported avail = avail_hdd - X (or 0, if X>avail_hdd)

     9. With shared space indicator and negative percent indicator (=-X%)
     - reported avail = avail_hdd - avail_hdd*X/100

     In all those cases total space is calculated as:
     - reported total = reported avail + calc_size

COPYRIGHT
     Copyright (C) 2026 Jakub Kruszona-Zawadzki, Saglabs SA

     This file is part of MooseFS.

     MooseFS  is  free	software; you can redistribute it and/or modify it under
     the terms of the GNU General Public License as published by the Free  Soft-
     ware Foundation, version 2 (only).

     MooseFS  is distributed in the hope that it will be useful, but WITHOUT ANY
     WARRANTY; without even the implied warranty of MERCHANTABILITY  or  FITNESS
     FOR  A  PARTICULAR PURPOSE. See the GNU General Public License for more de-
     tails.

     You should have received a copy of the GNU  General  Public  License  along
     with this program; if not, see <https://www.gnu.org/licenses/>.

SEE ALSO
     mfschunkserver(8), mfschunkserver.cfg(5)

MooseFS 4.59.1-1		    May 2026			   mfshdd.cfg(5)

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