.TH mfshdd.cfg "5" "September 2024" "MooseFS 4.56.6-1" "This is part of MooseFS"
.SH NAME
mfshdd.cfg \- list of MooseFS storage directories for \fBmfschunkserver\fP
.SH DESCRIPTION
The file \fBmfshdd.cfg\fP contains list of directories (mountpoints)
used for MooseFS storage.
.SH SYNTAX
.PP
Syntax is:
.TP
[\fB*\fP|\fB<\fP|\fB>\fP|\fB~\fP]\fIPATH\fP [\fISPACE OPTIONS\fP]
.PP
Lines starting with \fB#\fP character are ignored as comments.
.PP
Path can be prefixed with one or more special characters. These characters work as additional options.
.RS
.IP \fB*\fP
means this directory (hard drive) is "marked for removal" 
and all data will be replicated to other hard drives, usually on other chunkservers
.IP \fB<\fP
means that all data from this hard drive should be moved to other local hard drives
.IP \fB>\fP
means that all data from other local hard drives should be moved to this hard drive
.IP \fB~\fP
means that significant (more than 10% in less than a minute) change of total blocks count will not mark this drive as damaged (useful for compressed filesystems)
.RE
.PP
\fIPATH\fP is path to the mounting point of storage directory, usually a single hard drive.
.PP
\fISPACE OPTIONS\fP allow to define limits in used space and alter disk usage reporting. A \fISPACE OPTION\fP can be:
.IP
a positive space limit, indicating a space limit deifinition (i.e. only this amount of space on the indicated path should be used for chunk storage)
.IP
a negative space limit, indicating a reserved space definition (i.e. at least this amount of space should always be left free on the indicated path)
.IP
an equals '=' sign, optionally followed by a space limit indicator
.PP
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.
.PP
An equals sign indicates, that a disk is "shared" with another process 
(either 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. Additionaly, 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.
.PP
The presence or absence of \fISPACE OPTION\fP changes the way chunk server calculates available 
and used space on a given path.
.PP
Let's define 3 base values:
.br
total_hdd - total device size, as returned by statvfs
.br
avail_hdd - total available space, as returned by statvfs
.br
calc_size - used space (sum of chunk's disk usage)
.PP
When there is no \fISPACE OPTION\fP defined then total and available space are reported as follows:
.PP
- reported total = total_hdd
.br
- reported avail = avail_hdd 
.PP
Otherwise available space is calculated using formulas:
.PP
1. With constant reserved space (negative space limit -X)
.br
- reported avail = total_hdd - X - calc_size (or zero if X + calc_size > total_hdd)
.PP
2. With perecent of reserved space (negative space limit -X%)
.br
- reported avail = total_hdd - total_hdd*X/100 - calc_size (or zero if total_hdd*X/100 + calc_size > total_hdd)
.PP
3. With constant space limit (positive space limit X)
.br
- reported avail = X - calc_size (or zero if calc_size > X)
.PP
4. With percent space limit (positive space limit X%)
.br
- reported avail = total_hdd*X/100 - calc_size (or zero if calc_size > total_hdd*X/100)
.PP
5. With shared space indicator (= sign)
.br
- reported avail = avail_hdd
.PP
6. With shared space indicator and space indicator (=X)
.br
- reported avail = X (or avail_hdd if avail_hdd < X)
.PP
7. With shared space indicator and percent indicator (=X%)
.br
- reported avail = avail_hdd*X/100
.PP
8. With shared space indicator and negative space indicator (=-X)
.br
- reported avail = avail_hdd - X (or 0, if X>avail_hdd)
.PP
9. With shared space indicator and negative percent indicator (=-X%)
.br
- reported avail = avail_hdd - avail_hdd*X/100
.PP
In all those cases total space is calculated as:
.br
- reported total = reported avail + calc_size
.SH COPYRIGHT
Copyright (C) 2024 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 Software 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 details.

You should have received a copy of the GNU General Public License
along with MooseFS; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02111-1301, USA
or visit http://www.gnu.org/licenses/gpl-2.0.html
.SH "SEE ALSO"
.BR mfschunkserver (8),
.BR mfschunkserver.cfg (5)