NAME

pmempool-transform – Modify internal structure of a poolset.

SYNOPSIS

pmempool transform [options] <poolset_file_src> <poolset_file_dst>

DESCRIPTION

The pmempool transform command modifies internal structure of a poolset 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 poolset,
removing replicas - one or more replicas can be removed from the poolset,
reordering of replicas - the order of existing replicas can be changed.

Currently these operations are allowed only for pmemobj pools (see libpmemobj(3)).

The poolset_file_src argument provides the source poolset to be changed.

The poolset_file_dst argument points to the target poolset.

When adding or deleting replicas, the two poolset files can differ only in the definitions of replicas which are to be added or deleted. One cannot add and remove replicas in the same step. Only one of these operations can be performed at a time. Reordering replicas can be combined with any of them. Also, 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. 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.

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 poolset. 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 poolset. The first replica remains unchanged and the size of the pool is still 60M.

pmem.ioPersistent Memory Programming

PMDK man page

pmempool-transform(1)