MySQL分支 Percona 5.6.15 发布
Percona 为 MySQL 数据库服务器进行了改进，在功能和性能上较 MySQL 有着很显著的提升。该版本提升了在高负载情况下的 InnoDB 的性能、为 DBA 提供一些非常有用的性能诊断工具；另外有更多的参数和命令来控制服务器行为。
Percona Server 只包含 MySQL 的服务器版，并没有提供相应对 MySQL 的 Connector 和 GUI 工具进行改进。
Percona Server 使用了一些 google-mysql-tools, Proven Scaling, Open Query 对 MySQL 进行改造。
与内置的 MySQL 存储引擎相比，XtraDB 提供了一些极大的改进，但它不是一款独立产品，也无法轻松放入现有 MySQL 安装。因此，如果您想使用这款新引擎，则必须使用提供它的产品。
Percona Server 就是这样一款产品，由领先的 MySQL 咨询公司 Percona 发布。Percona Server 是一款独立的数据库产品，为用户提供了换出其 MySQL 安装并换入 Percona Server 产品的能力。通过这样做，就可以利用 XtraDB 存储引擎。Percona Server 声称可以完全与 MySQL 兼容，因此从理论上讲，您无需更改软件中的任何代码。这确实是一个很大的优势，适合在您寻找快速性能改进时控制质量。因此，采用 Percona Server 的一个很好的理由是，利用 XtraDB 引擎来尽可能地减少代码更改。
此外，他们是 XtraDB 存储引擎的原作者。Percona 将此代码用作开源代码，因此您可以在其他产品中找到它，但引擎的最初创建者与编写此产品的是同一个人，所以您可以随心所欲地使用此信息。
下面是 Percona Server 的声明，该声明来自它们自己的网站：
- 可扩展性：处理更多事务；在强大的服务器上进行扩展
- 性能：使用了 XtraDB 的 Percona Server 速度非常快
- 可靠性：避免损坏，提供崩溃安全 (crash-safe) 复制
- 管理：在线备份，在线表格导入/导出
- 诊断：高级分析和检测
- 灵活性：可变的页面大小，改进的缓冲池管理
Percona 团队的最终声明是 “Percona Server 是由 Oracle 发布的最接近官方 MySQL Enterprise 发行版的版本”，因此与其他更改了大量基本核心 MySQL 代码的分支有所区别。Percona Server 的一个缺点是他们自己管理代码，不接受外部开发人员的贡献，以这种方式确保他们对产品中所包含功能的控制。
同步基于 MySQL 5.6.15/5.5.34/5.1.73.此版本增强了线程池在高并发下的性能，增强mysqlbinlog支持SSL和压缩支持，降低了信息模式里用户 统计的性能开销及一些 Bug 修正。
5.6.15完全改进：
New Features
Thread Pool high priority scheduling is now enabled by default by changing the default thread_pool_high_prio_tickets value from0to4294967295.
Percona Server now supports Low priority queue throttling. This feature should improve Thread Pool performance under high concurrency in a situation when thread groups are oversubscribed.
Introduced new thread_pool_high_prio_mode to provide more fine-grained control over high priority scheduling either globally or per connection in Thread Pool.
Percona Server has extended mysqlbinlog to provideSSLand compression support.
Percona Server has reduced the performance overhead of the User Statistics feature.
Bugs Fixed
INSTALL PLUGINstatement would crash server if User Statistics were enabled. Bug fixed #1011047.
innodb_log_checksum_algorithm did not have any effect when set frommy.cnfor mysqld command line, it would have effect only if set dynamically. Bug fixed #1248505.
Server would crash on shutdown if Atomic write support for Fusion-io devices feature is enabled. Bug fixed #1255628 (Jan Lindström).
Percona Server would crash when data was select from XTRADB_RSEG table when InnoDB system table space was initialized with lower then default number of rollback segments. Bug fixed #1260259.
Certain types of workloads (large result sets, blobs, slow clients) can have longer waits on network I/O (socket reads and writes). Whenever server waits, this should be communicated to the Thread Pool, so it can start new query by either waking a waiting thread or sometimes creating a new one. Ported MariaDB patch MDEV-156, bug fixed #1159743.
mysqldump --innodb-optimize-keyswas generating incorrectCREATE TABLEstatements for partitioned tables. Bug fixed #1233841.
Fixed errors when server was compiled with-DWITH_LIBWRAP=ONoption. Bug fixed #1240442.
Ifinnobase_atomic_writeswas used on separate undo files that do not exists would lead to operating system error. Bug fixed #1255638 (Jan Lindström).
Default value for thread_pool_max_threads has been changed from500to100 000(the maximum supported number of connections), because limiting the total number of threads in the Thread Pool can result in deadlocks and uneven distribution of worker threads between thread groups in case of stalled connections. Bug fixed #1258097.
PURGE CHANGED_PAGE_BITMAPS BEFOREstatement would delete the changed page data after the specified LSN and up to the start of the next bitmap file. If this data were to be used for fast incremental backups, its absence would cause Percona XtraBackup to fall back to the full-scan incremental backup mode. Bug fixed #1260035 (Andrew Gaul).
Server performance could degrade under heavy load or it could deadlock on shutdown while performing purge. Bug fixed #1236696.
Server could crash under heavy load if InnoDB compression was used. Bug fixed #1240371.
Redo log checksum mismatches would be diagnosed using the data page checksum algorithm setting instead of redo log checksum algorithm one. Bug fixed #1250148.
Other bugs fixed: bug #1082333, bug #1260945, bug #1248046, bug #1243067, bug #1238563, bug #1258154 (upstream bug #71092), bug #1242748, bug #1239062, bug #1200788, bug #1193319, bug #1240044.