PMEMPOOL-TRANSFORM(1)

NAME

pmempool-transform - Modify internal structure of a pool set.

SYNOPSIS

    pmempool transform [options] <poolset_file_src> <poolset_file_dst>

DESCRIPTION

The pmempool transform command modifies internal structure of a pool set defined by the poolset_file_src file, according to a structure described in the poolset_file_dst file.

The following operations are supported:

•   adding replicas - one or more new replicas can be added and synchronized with other replicas in the pool set,

•   removing replicas - one or more replicas can be removed from the pool set ,

•   adding or removing pool set options.

Only one of the above operations can be performed at a time.

Currently adding and removing replicas are allowed only for pmemobj pools (see libpmemobj(7)).

The poolset_file_src argument provides the source pool set to be changed.

The poolset_file_dst argument points to the target pool set.

When adding or deleting replicas, the two pool set files can differ only in the definitions of replicas which are to be added or deleted. When adding or removing pool set options (see poolset(5)), the rest of both pool set files have to be of the same structure. The operation of adding/removing a pool set option can be performed on a pool set with local replicas only. To add/remove a pool set option to/from a pool set with remote replicas, one has to remove the remote replicas first, then add/remove the option, and finally recreate the remote replicas having added/removed the pool set option to/from the remote replicas' poolset files. To add a replica it is necessary for its effective size to match or exceed the pool size. Otherwise the whole operation fails and no changes are applied. If none of the poolset options is used, the effective size of a replica is the sum of sizes of all its part files decreased by 4096 bytes per each part file. The 4096 bytes of each part file is utilized for storing internal metadata of the pool part files. If the option SINGLEHDR is used, the effective size of a replica is the sum of sizes of all its part files decreased once by 4096 bytes. In this case only the first part contains internal metadata. If the option NOHDRS is used, the effective size of a replica is the sum of sizes of all its part files. In this case none of the parts contains internal metadata.

  Available options:

-d, --dry-run
    Enable dry run mode. In this mode no changes are applied, only check for viability of the operation is performed.

-v, --verbose
    Increase verbosity level.

-h, --help
    Display help message and exit.

EXAMPLES

  Example 1.

Let files /path/poolset_file_src and /path/poolset_file_dst have the following contents:

    PMEMPOOLSET
    20M /0/partfile1
    20M /0/partfile2
    25M /0/partfile3
    REPLICA
    40M /1/partfile1
    20M /1/partfile2

    PMEMPOOLSET
    20M /0/partfile1
    20M /0/partfile2
    25M /0/partfile3
    REPLICA
    40M /1/partfile1
    20M /1/partfile2
    REPLICA
    50M /2/partfile1
    20M /2/partfile2

Then, the command

pmempool transform /path/poolset_file_src /path/poolset_file_dst

adds a replica to the pool set. All other replicas remain unchanged and the size of the pool remains 60M.

  Example 2.

Let files /path/poolset_file_src and /path/poolset_file_dst have the following contents:

    PMEMPOOLSET
    20M /0/partfile1
    20M /0/partfile2
    25M /0/partfile3
    REPLICA
    40M /1/partfile1
    20M /1/partfile2

    PMEMPOOLSET
    20M /0/partfile1
    20M /0/partfile2
    25M /0/partfile3

Then

pmempool_transform /path/poolset_file_src /path/poolset_file_dst

deletes the second replica from the pool set. The first replica remains unchanged and the size of the pool is still 60M.

SEE ALSO

pmempool(1), libpmemblk(7), libpmemlog(7), libpmempool(7) and <https://pmem.io>