The xbstream binary¶
To support simultaneous compression and streaming, a new custom streaming format called xbstream was introduced to Percona XtraBackup in addition to the TAR format. That was required to overcome some limitations of traditional archive formats such as tar, cpio and others which did not allow streaming dynamically generated files, for example dynamically compressed files. Other advantages of xbstream over traditional streaming/archive format include ability to stream multiple files concurrently (so it is possible to use streaming in the xbstream format together with the –parallel option) and more compact data storage.
This utility has a tar-like interface:
-
with the
-xoption it extracts files from the stream read from its standard input to the current directory unless specified otherwise with the-coption. Support for parallel extraction with the--paralleloption has been implemented in Percona XtraBackup 2.4.7. -
with the
-coption it streams files specified on the command line to its standard output. -
with the
--decrypt=ALGOoption specified xbstream will automatically decrypt encrypted files when extracting input stream. Supported values for this option are:AES128,AES192, andAES256. Either--encrypt-keyor--encrypt-key-fileoptions must be specified to provide encryption key, but not both. This option has been implemented in Percona XtraBackup 2.4.7. -
with the
--encrypt-threadsoption you can specify the number of threads for parallel data encryption. The default value is1. This option has been implemented in Percona XtraBackup 2.4.7. -
the
--encrypt-keyoption is used to specify the encryption key that will be used. It can’t be used with--encrypt-key-fileoption because they are mutually exclusive. This option has been implemented in Percona XtraBackup 2.4.7. -
the
--encrypt-key-fileoption is used to specify the file that contains the encryption key. It can’t be used with--encrypt-keyoption because they are mutually exclusive. This option has been implemented in Percona XtraBackup 2.4.7.
The utility also tries to minimize its impact on the OS page cache by using the
appropriate posix_fadvise() calls when available.
When compression is enabled with xtrabackup all data is being compressed,
including the transaction log file and meta data files, using the specified
compression algorithm. The only currently supported algorithm is quicklz.
The resulting files have the qpress archive format, i.e., every \*.qp file
produced by xtrabackup is essentially a one-file qpress archive and can be
extracted and uncompressed by the qpress file archiver. This means that there is no need to decompress
entire backup to restore a single table as with tar.gz.
Files can be decompressed using the qpress tool that can be downloaded from here. Qpress supports multi-threaded decompression.
The default size of the chunk file is 10MB.
Note
Use --read-buffer-size to adjust the chunk size.
If you use encryption, specify both the --read-buffer-size and --encrypt-chunk-size options to adjust the chunk size.