Skip to content

Commit

Permalink
xfs: update mount options documentation
Browse files Browse the repository at this point in the history 
Because it's horribly out of date.

And mark various deprecated options as deprecated and give them a
removal date.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Signed-off-by: Ben Myers <bpm@sgi.com>
  • Loading branch information
Dave Chinner authored and Ben Myers committed Jul 9, 2013
1 parent 862a629 commit 3e5b7d8
Showing 1 changed file with 209 additions and 108 deletions.
317 changes: 209 additions & 108 deletions Documentation/filesystems/xfs.txt
View file
Original file line number Diff line number Diff line change
Expand Up @@ -18,104 +18,137 @@ Mount Options
=============

When mounting an XFS filesystem, the following options are accepted.
For boolean mount options, the names with the (*) suffix is the
default behaviour.

allocsize=size
Sets the buffered I/O end-of-file preallocation size when
doing delayed allocation writeout (default size is 64KiB).
Valid values for this option are page size (typically 4KiB)
through to 1GiB, inclusive, in power-of-2 increments.

attr2/noattr2
The options enable/disable (default is disabled for backward
compatibility on-disk) an "opportunistic" improvement to be
made in the way inline extended attributes are stored on-disk.
When the new form is used for the first time (by setting or
removing extended attributes) the on-disk superblock feature
bit field will be updated to reflect this format being in use.
The default behaviour is for dynamic end-of-file
preallocation size, which uses a set of heuristics to
optimise the preallocation size based on the current
allocation patterns within the file and the access patterns
to the file. Specifying a fixed allocsize value turns off
the dynamic behaviour.

attr2
noattr2
The options enable/disable an "opportunistic" improvement to
be made in the way inline extended attributes are stored
on-disk. When the new form is used for the first time when
attr2 is selected (either when setting or removing extended
attributes) the on-disk superblock feature bit field will be
updated to reflect this format being in use.

The default behaviour is determined by the on-disk feature
bit indicating that attr2 behaviour is active. If either
mount option it set, then that becomes the new default used
by the filesystem.

CRC enabled filesystems always use the attr2 format, and so
will reject the noattr2 mount option if it is set.

barrier
Enables the use of block layer write barriers for writes into
the journal and unwritten extent conversion. This allows for
drive level write caching to be enabled, for devices that
support write barriers.
barrier (*)
nobarrier
Enables/disables the use of block layer write barriers for
writes into the journal and for data integrity operations.
This allows for drive level write caching to be enabled, for
devices that support write barriers.

discard
Issue command to let the block device reclaim space freed by the
filesystem. This is useful for SSD devices, thinly provisioned
LUNs and virtual machine images, but may have a performance
impact.

dmapi
Enable the DMAPI (Data Management API) event callouts.
Use with the "mtpt" option.

grpid/bsdgroups and nogrpid/sysvgroups
These options define what group ID a newly created file gets.
When grpid is set, it takes the group ID of the directory in
which it is created; otherwise (the default) it takes the fsgid
of the current process, unless the directory has the setgid bit
set, in which case it takes the gid from the parent directory,
and also gets the setgid bit set if it is a directory itself.

ihashsize=value
In memory inode hashes have been removed, so this option has
no function as of August 2007. Option is deprecated.

ikeep/noikeep
When ikeep is specified, XFS does not delete empty inode clusters
and keeps them around on disk. ikeep is the traditional XFS
behaviour. When noikeep is specified, empty inode clusters
are returned to the free space pool. The default is noikeep for
non-DMAPI mounts, while ikeep is the default when DMAPI is in use.

inode64
Indicates that XFS is allowed to create inodes at any location
in the filesystem, including those which will result in inode
numbers occupying more than 32 bits of significance. This is
the default allocation option. Applications which do not handle
inode numbers bigger than 32 bits, should use inode32 option.
nodiscard (*)
Enable/disable the issuing of commands to let the block
device reclaim space freed by the filesystem. This is
useful for SSD devices, thinly provisioned LUNs and virtual
machine images, but may have a performance impact.

Note: It is currently recommended that you use the fstrim
application to discard unused blocks rather than the discard
mount option because the performance impact of this option
is quite severe.

grpid/bsdgroups
nogrpid/sysvgroups (*)
These options define what group ID a newly created file
gets. When grpid is set, it takes the group ID of the
directory in which it is created; otherwise it takes the
fsgid of the current process, unless the directory has the
setgid bit set, in which case it takes the gid from the
parent directory, and also gets the setgid bit set if it is
a directory itself.

filestreams
Make the data allocator use the filestreams allocation mode
across the entire filesystem rather than just on directories
configured to use it.

ikeep
noikeep (*)
When ikeep is specified, XFS does not delete empty inode
clusters and keeps them around on disk. When noikeep is
specified, empty inode clusters are returned to the free
space pool.

inode32
Indicates that XFS is limited to create inodes at locations which
will not result in inode numbers with more than 32 bits of
significance. This is provided for backwards compatibility, since
64 bits inode numbers might cause problems for some applications
that cannot handle large inode numbers.

largeio/nolargeio
inode64 (*)
When inode32 is specified, it indicates that XFS limits
inode creation to locations which will not result in inode
numbers with more than 32 bits of significance.

When inode64 is specified, it indicates that XFS is allowed
to create inodes at any location in the filesystem,
including those which will result in inode numbers occupying
more than 32 bits of significance.

inode32 is provided for backwards compatibility with older
systems and applications, since 64 bits inode numbers might
cause problems for some applications that cannot handle
large inode numbers. If applications are in use which do
not handle inode numbers bigger than 32 bits, the inode32
option should be specified.


largeio
nolargeio (*)
If "nolargeio" is specified, the optimal I/O reported in
st_blksize by stat(2) will be as small as possible to allow user
applications to avoid inefficient read/modify/write I/O.
If "largeio" specified, a filesystem that has a "swidth" specified
will return the "swidth" value (in bytes) in st_blksize. If the
filesystem does not have a "swidth" specified but does specify
an "allocsize" then "allocsize" (in bytes) will be returned
instead.
If neither of these two options are specified, then filesystem
will behave as if "nolargeio" was specified.
st_blksize by stat(2) will be as small as possible to allow
user applications to avoid inefficient read/modify/write
I/O. This is typically the page size of the machine, as
this is the granularity of the page cache.

If "largeio" specified, a filesystem that was created with a
"swidth" specified will return the "swidth" value (in bytes)
in st_blksize. If the filesystem does not have a "swidth"
specified but does specify an "allocsize" then "allocsize"
(in bytes) will be returned instead. Otherwise the behaviour
is the same as if "nolargeio" was specified.

logbufs=value
Set the number of in-memory log buffers. Valid numbers range
from 2-8 inclusive.
The default value is 8 buffers for filesystems with a
blocksize of 64KiB, 4 buffers for filesystems with a blocksize
of 32KiB, 3 buffers for filesystems with a blocksize of 16KiB
and 2 buffers for all other configurations. Increasing the
number of buffers may increase performance on some workloads
at the cost of the memory used for the additional log buffers
and their associated control structures.
Set the number of in-memory log buffers. Valid numbers
range from 2-8 inclusive.

The default value is 8 buffers.

If the memory cost of 8 log buffers is too high on small
systems, then it may be reduced at some cost to performance
on metadata intensive workloads. The logbsize option below
controls the size of each buffer and so is also relevent to
this case.

logbsize=value
Set the size of each in-memory log buffer.
Size may be specified in bytes, or in kilobytes with a "k" suffix.
Valid sizes for version 1 and version 2 logs are 16384 (16k) and
32768 (32k). Valid sizes for version 2 logs also include
65536 (64k), 131072 (128k) and 262144 (256k).
The default value for machines with more than 32MiB of memory
is 32768, machines with less memory use 16384 by default.
Set the size of each in-memory log buffer. The size may be
specified in bytes, or in kilobytes with a "k" suffix.
Valid sizes for version 1 and version 2 logs are 16384 (16k)
and 32768 (32k). Valid sizes for version 2 logs also
include 65536 (64k), 131072 (128k) and 262144 (256k). The
logbsize must be an integer multiple of the log
stripe unit configured at mkfs time.

The default value for for version 1 logs is 32768, while the
default value for version 2 logs is MAX(32768, log_sunit).

logdev=device and rtdev=device
Use an external log (metadata journal) and/or real-time device.
Expand All @@ -124,16 +157,11 @@ When mounting an XFS filesystem, the following options are accepted.
optional, and the log section can be separate from the data
section or contained within it.

mtpt=mountpoint
Use with the "dmapi" option. The value specified here will be
included in the DMAPI mount event, and should be the path of
the actual mountpoint that is used.

noalign
Data allocations will not be aligned at stripe unit boundaries.

noatime
Access timestamps are not updated when a file is read.
Data allocations will not be aligned at stripe unit
boundaries. This is only relevant to filesystems created
with non-zero data alignment parameters (sunit, swidth) by
mkfs.

norecovery
The filesystem will be mounted without running log recovery.
Expand All @@ -144,8 +172,14 @@ When mounting an XFS filesystem, the following options are accepted.
the mount will fail.

nouuid
Don't check for double mounted file systems using the file system uuid.
This is useful to mount LVM snapshot volumes.
Don't check for double mounted file systems using the file
system uuid. This is useful to mount LVM snapshot volumes,
and often used in combination with "norecovery" for mounting
read-only snapshots.

noquota
Forcibly turns off all quota accounting and enforcement
within the filesystem.

uquota/usrquota/uqnoenforce/quota
User disk quota accounting enabled, and limits (optionally)
Expand All @@ -160,24 +194,64 @@ When mounting an XFS filesystem, the following options are accepted.
enforced. Refer to xfs_quota(8) for further details.

sunit=value and swidth=value
Used to specify the stripe unit and width for a RAID device or
a stripe volume. "value" must be specified in 512-byte block
units.
If this option is not specified and the filesystem was made on
a stripe volume or the stripe width or unit were specified for
the RAID device at mkfs time, then the mount system call will
restore the value from the superblock. For filesystems that
are made directly on RAID devices, these options can be used
to override the information in the superblock if the underlying
disk layout changes after the filesystem has been created.
The "swidth" option is required if the "sunit" option has been
specified, and must be a multiple of the "sunit" value.
Used to specify the stripe unit and width for a RAID device
or a stripe volume. "value" must be specified in 512-byte
block units. These options are only relevant to filesystems
that were created with non-zero data alignment parameters.

The sunit and swidth parameters specified must be compatible
with the existing filesystem alignment characteristics. In
general, that means the only valid changes to sunit are
increasing it by a power-of-2 multiple. Valid swidth values
are any integer multiple of a valid sunit value.

Typically the only time these mount options are necessary if
after an underlying RAID device has had it's geometry
modified, such as adding a new disk to a RAID5 lun and
reshaping it.

swalloc
Data allocations will be rounded up to stripe width boundaries
when the current end of file is being extended and the file
size is larger than the stripe width size.

wsync
When specified, all filesystem namespace operations are
executed synchronously. This ensures that when the namespace
operation (create, unlink, etc) completes, the change to the
namespace is on stable storage. This is useful in HA setups
where failover must not result in clients seeing
inconsistent namespace presentation during or after a
failover event.


Deprecated Mount Options
========================

delaylog/nodelaylog
Delayed logging is the only logging method that XFS supports
now, so these mount options are now ignored.

Due for removal in 3.12.

ihashsize=value
In memory inode hashes have been removed, so this option has
no function as of August 2007. Option is deprecated.

Due for removal in 3.12.

irixsgid
This behaviour is now controlled by a sysctl, so the mount
option is ignored.

Due for removal in 3.12.

osyncisdsync
osyncisosync
O_SYNC and O_DSYNC are fully supported, so there is no need
for these options any more.

Due for removal in 3.12.

sysctls
=======
Expand All @@ -189,15 +263,20 @@ The following sysctls are available for the XFS filesystem:
in /proc/fs/xfs/stat. It then immediately resets to "0".

fs.xfs.xfssyncd_centisecs (Min: 100 Default: 3000 Max: 720000)
The interval at which the xfssyncd thread flushes metadata
out to disk. This thread will flush log activity out, and
do some processing on unlinked inodes.
The interval at which the filesystem flushes metadata
out to disk and runs internal cache cleanup routines.

fs.xfs.xfsbufd_centisecs (Min: 50 Default: 100 Max: 3000)
The interval at which xfsbufd scans the dirty metadata buffers list.
fs.xfs.filestream_centisecs (Min: 1 Default: 3000 Max: 360000)
The interval at which the filesystem ages filestreams cache
references and returns timed-out AGs back to the free stream
pool.

fs.xfs.age_buffer_centisecs (Min: 100 Default: 1500 Max: 720000)
The age at which xfsbufd flushes dirty metadata buffers to disk.
fs.xfs.speculative_prealloc_lifetime
(Units: seconds Min: 1 Default: 300 Max: 86400)
The interval at which the background scanning for inodes
with unused speculative preallocation runs. The scan
removes unused preallocation from clean inodes and releases
the unused space back to the free pool.

fs.xfs.error_level (Min: 0 Default: 3 Max: 11)
A volume knob for error reporting when internal errors occur.
Expand Down Expand Up @@ -254,9 +333,31 @@ The following sysctls are available for the XFS filesystem:
by the xfs_io(8) chattr command on a directory to be
inherited by files in that directory.

fs.xfs.inherit_nodefrag (Min: 0 Default: 1 Max: 1)
Setting this to "1" will cause the "nodefrag" flag set
by the xfs_io(8) chattr command on a directory to be
inherited by files in that directory.

fs.xfs.rotorstep (Min: 1 Default: 1 Max: 256)
In "inode32" allocation mode, this option determines how many
files the allocator attempts to allocate in the same allocation
group before moving to the next allocation group. The intent
is to control the rate at which the allocator moves between
allocation groups when allocating extents for new files.

Deprecated Sysctls
==================

fs.xfs.xfsbufd_centisecs (Min: 50 Default: 100 Max: 3000)
Dirty metadata is now tracked by the log subsystem and
flushing is driven by log space and idling demands. The
xfsbufd no longer exists, so this syctl does nothing.

Due for removal in 3.14.

fs.xfs.age_buffer_centisecs (Min: 100 Default: 1500 Max: 720000)
Dirty metadata is now tracked by the log subsystem and
flushing is driven by log space and idling demands. The
xfsbufd no longer exists, so this syctl does nothing.

Due for removal in 3.14.

0 comments on commit 3e5b7d8

Please sign in to comment.