Provided by: libpmem1_1.6.1-1ubuntu1_amd64 bug

NAME

       poolset - persistent memory pool configuration file format

SYNOPSIS

              mypool.set

DESCRIPTION

       Depending  on the configuration of the system, the available non-volatile memory space may
       be divided into  multiple  memory  devices.   In  such  case,  the  maximum  size  of  the
       transactional  object  store  could  be limited by the capacity of a single memory device.
       Therefore, libpmemobj(7), libpmemblk(7) and libpmemlog(7)  allow  building  object  stores
       spanning  multiple  memory  devices  by  creation of persistent memory pools consisting of
       multiple files, where each part of such a pool set may be stored on a different pmem-aware
       filesystem.

       To  improve  reliability  and eliminate single point of failure, libpmemobj(7) also allows
       all the data written to a persistent memory pool to be copied  to  local  or  remote  pool
       replicas,  thereby providing backup for the persistent memory pool by producing a mirrored
       pool set.  In practice, the pool replicas may  be  considered  as  binary  copies  of  the
       “master” pool set.  Data replication is not supported in libpmemblk(7) and libpmemlog(7).

       The  set file for each type of pool is a plain text file.  Lines in the file are formatted
       as follows:

       · The first line of the file must be the literal string “PMEMPOOLSET”

       · The pool parts are specified, one per line, in the format:

         size pathname

       · Replica sections, if any, start with the literal string “REPLICA”.  See REPLICAS, below,
         for further details.

       · Pool  set options, if any, start with literal string OPTION.  See POOL SET OPTIONS below
         for details.

       · Lines starting with “#” are considered comments and are ignored.

       The size must be compliant with the format specified in IEC 80000-13,  IEEE  1541  or  the
       Metric  Interchange  Format.   These standards accept SI units with obligatory B - kB, MB,
       GB, ...  (multiplier by 1000) suffixes, and IEC units with optional “iB” - KiB, MiB,  GiB,
       ..., K, M, G, ... - (multiplier by 1024) suffixes.

       pathname must be an absolute pathname.

       The  pathname  of  a  part  can  point  to a Device DAX.  Device DAX is the device-centric
       analogue of Filesystem DAX.  It allows memory ranges to be allocated  and  mapped  without
       need of an intervening file system.

       Pools created on Device DAX have additional options and restrictions:

       · The  size  may  be  set  to  “AUTO”,  in  which  case  the  size  of  the device will be
         automatically resolved at pool creation time.

       · To concatenate more than one Device DAX device into a single pool  set,  the  configured
         internal alignment of the devices must be 4KiB, unless the SINGLEHDR or NOHDRS option is
         used in the pool set file.  See POOL SET OPTIONS below for details.

       Please see ndctl-create-namespace(1) for more information on Device DAX, including how  to
       configure desired alignment.

       The minimum file size of each part of the pool set is defined as follows:

       · For block pools, as PMEMBLK_MIN_PART in <libpmemblk.h>

       · For object pools, as PMEMOBJ_MIN_PART in <libpmemobj.h>

       · For log pools, as PMEMLOG_MIN_PART in <libpmemlog.h>

       The net pool size of the pool set is equal to:

              net_pool_size = sum_over_all_parts(page_aligned_part_size - 4KiB) + 4KiB

       where

              page_aligned_part_size = part_size & ~(page_size - 1)

       Note that page size is OS specific.  For more information please see sysconf(3).

       The minimum net pool size of a pool set is defined as follows:

       · For block pools, as PMEMBLK_MIN_POOL in <libpmemblk.h>

       · For object pools, as PMEMOBJ_MIN_POOL in <libpmemobj.h>

       · For log pools, as PMEMLOG_MIN_POOL in <libpmemlog.h>

       Here is an example “mypool.set” file:

              PMEMPOOLSET
              OPTION NOHDRS
              100G /mountpoint0/myfile.part0
              200G /mountpoint1/myfile.part1
              400G /mountpoint2/myfile.part2

       The files in the set may be created by running one of the following commands.  To create a
       block pool:

              $ pmempool create blk <bsize> mypool.set

       To create a log pool:

              $ pmempool create log mypool.set

REPLICAS

       Sections defining replica sets are optional.  There may be multiple replica sections.

       Local replica sections begin with a line containing only  the  literal  string  “REPLICA”,
       followed by one or more pool part lines as described above.

       Remote  replica  sections consist of the REPLICA keyword, followed on the same line by the
       address of a remote host and a relative path to a remote pool set file:

              REPLICA [<user>@]<hostname> [<relative-path>/]<remote-pool-set-file>

       · hostname must be in the format recognized by the ssh(1) remote login client

       · pathname is relative to the root config directory on the target node - see librpmem(3)

       There are no other lines in the remote replica section - the REPLICA line defines a remote
       replica entirely.

       Here is an example “myobjpool.set” file with replicas:

              PMEMPOOLSET
              100G /mountpoint0/myfile.part0
              200G /mountpoint1/myfile.part1
              400G /mountpoint2/myfile.part2

              # local replica
              REPLICA
              500G /mountpoint3/mymirror.part0
              200G /mountpoint4/mymirror.part1

              # remote replica
              REPLICA user@example.com remote-objpool.set

       The files in the object pool set may be created by running the following command:

              $ pmempool create --layout="mylayout" obj myobjpool.set

       Remote  replica  cannot  have  replicas,  i.e. a  remote  pool  set file cannot define any
       replicas.

POOL SET OPTIONS

       Pool set options can appear anywhere after the line with  PMEMPOOLSET  string.   Pool  set
       file can contain several pool set options.  The following options are supported:

       · SINGLEHDR

       · NOHDRS

       If  the  SINGLEHDR  option  is used, only the first part in each replica contains the pool
       part internal metadata.  In that case the effective size of a replica is the sum of  sizes
       of all its part files decreased once by 4096 bytes.

       The  NOHDRS  option  can  appear  only in the remote pool set file, when librpmem does not
       serve as a means of replication for libpmemobj pool.  In that case none of the pool  parts
       contains  internal  metadata.  The effective size of such a replica is the sum of sizes of
       all its part files.

       Options SINGLEHDR and NOHDRS are mutually exclusive.  If both are specified in a pool  set
       file, creating or opening the pool will fail with an error.

       When  using  the  SINGLEHDR or NOHDRS option, one can concatenate more than one Device DAX
       devices with any internal alignments in one replica.

       The SINGLEHDR option concerns only replicas that are local to the pool set file.  That  is
       if  one wants to create a pool set with the SINGLEHDR option and with remote replicas, one
       has to add this option to the local pool set file as well as to every single  remote  pool
       set file.

       Using  the  SINGLEHDR  and  NOHDRS  options  has important implications for data integrity
       checking and recoverability in case of a pool set damage.   See  pmempool_sync()  API  for
       more information about pool set recovery.

DIRECTORIES

       Providing a directory as a part's pathname allows the pool to dynamically create files and
       consequently removes the user-imposed limit on the size of the pool.

       The size argument of a part in a directory poolset becomes the size of the  address  space
       reservation  required  for  the  pool.   In  other words, the size argument is the maximum
       theoretical size of the mapping.  This value can be freely increased between instances  of
       the  application,  but decreasing it below the real required space will result in an error
       when attempting to open the pool.

       The directory must NOT contain user created files  with  extension  .pmem,  otherwise  the
       behavior  is  undefined.   If a file created by the library within the directory is in any
       way altered (resized, renamed) the behavior is undefined.

       A directory poolset must exclusively use directories to specify paths  -  combining  files
       and  directories  will  result  in  an error.  A single replica can consist of one or more
       directories.  If there are multiple directories, the address space reservation is equal to
       the sum of the sizes.

       The  order  in  which  the  files  are created is unspecified, but the library will try to
       maintain equal usage of the directories.

       By default pools grow in 128 megabyte increments.

       Only poolsets with the SINGLEHDR option can safely use directories.

NOTES

       Creation of all the parts of the pool set and the associated replica sets can be done with
       the  pmemobj_create(3),  pmemblk_create(3)  or pmemlog_create(3) function, or by using the
       pmempool(1) utility.

       Restoring data from a local or remote replica can be done by  using  the  pmempool-sync(1)
       command or the pmempool_sync() API from the libpmempool(3) library.

       Modifications   of   a   pool   set   file   configuration   can  be  done  by  using  the
       pmempool-transform(1) command or the  pmempool_transform()  API  from  the  libpmempool(3)
       library.

       When  creating a pool set consisting of multiple files, or when creating a replicated pool
       set, the path argument passed to pmemobj_create(3), pmemblk_create(3) or pmemlog_create(3)
       must  point  to  the special set file that defines the pool layout and the location of all
       the parts of the pool set.

       When opening a pool set consisting of multiple files, or when opening  a  replicated  pool
       set,  the path argument passed to pmemobj_open(3), pmemblk_open(3) or pmemlog_open(3) must
       point to the same set file that was used for pool set creation.

SEE ALSO

       ndctl-create-namespace(1),   pmemblk_create(3),   pmemlog_create(3),    pmemobj_create(3),
       sysconf(3), libpmemblk(7), libpmemlog(7), libpmemobj(7) and <http://pmem.io>