测试环境

操作系统：CentOS Linux 7
CPU核数：8C
内存：32G
数据文件已使用大小：9.5G
dd速度

备份语句

backup database full to bak backupset '/dmbak/5236/bak';
backup database full to bak_level_1 backupset '/dmbak/5236/bak_level_1' compressed level 1;
backup database full to bak_level_2 backupset '/dmbak/5236/bak_level_2' compressed level 2;
backup database full to bak_level_3 backupset '/dmbak/5236/bak_level_3' compressed level 3;
backup database full to bak_level_4 backupset '/dmbak/5236/bak_level_4' compressed level 4;
backup database full to bak_level_5 backupset '/dmbak/5236/bak_level_5' compressed level 5;
backup database full to bak_level_6 backupset '/dmbak/5236/bak_level_6' compressed level 6;
backup database full to bak_level_7 backupset '/dmbak/5236/bak_level_7' compressed level 7;
backup database full to bak_level_8 backupset '/dmbak/5236/bak_level_8' compressed level 8;
backup database full to bak_level_9 backupset '/dmbak/5236/bak_level_9' compressed level 9;

执行结果对比

压缩级别总结

本次进行两次测试，备份文件大小几乎没有变化，但花费时间变化较大，可能跟测试虚拟机IO有关。
两次测试加上之前生成备份情况得出，不进行压缩时，备份文件与实际数据文件使用大小相近；
备份级别越高，生成备份文件占用空间越小，，完成备份时间越长。
备份级别较低，比如小于5时，备份文件大小和完成时间变化并不太明显，级别大于5时，花费时间跨度较大。
日常备份和创建备份作业时根据磁盘空间大小和备份时长判断使用压缩级别，如果磁盘空间相对宽松，建议level级别小于5