For example, if the estimated deduplication ratio is greater than 2, you might see deduplication space savings.例如，如果估计的重复数据删除比率大于2，你可能会看到重复数据删除节省空间。 In the example shown in Listing 1, the deduplication ratio is less than 2, so enabling dedup is not recommended.在清单1中所示的例子，重复数据删除比率小于2，因此使dedup是不推荐。
Listing 1: Determining the Deduplication Ratio 清单1：确定重复数据删除比率
# zdb -S tank ＃ZDB小号罐
Simulated DDT histogram:模拟滴滴涕直方图：
bucket allocated referenced斗分配引用
refcnt blocks LSIZE PSIZE DSIZE blocks LSIZE PSIZE DSIZE refcnt块LSIZE PSIZE DSIZE块LSIZE PSIZE DSIZE
------ ------ ----- ----- ----- ------ ----- ----- ----- ------ ------ ----- ----- ----- ------ ----- ----- -----
1 2.27M 239G 188G 194G 2.27M 239G 188G 194G 1 2.27M 239G 188G 194G 2.27M 239G 188G 194G
2 327K 34.3G 27.8G 28.1G 698K 73.3G 59.2G 59.9G 2 327K 34.3G 27.8G 28.1G 698K 73.3G 59.2G 59.9G
4 30.1K 2.91G 2.10G 2.11G 152K 14.9G 10.6G 10.6G 4 30.1K 2.91G 2.10G 2.11G 152K 14.9G 10.6G 10.6G
8 7.73K 691M 529M 529M 74.5K 6.25G 4.79G 4.80G 8 7.73K 691M 529M 529M 74.5K 6.25G 4.79G 4.80G
16 673 43.7M 25.8M 25.9M 13.1K 822M 492M 494M 16 673 43.7M 25.8M 25.9M 13.1K 822M 492M 494M
32 197 12.3M 7.02M 7.03M 7.66K 480M 269M 270M 32 197 12.3M 7.02M 7.03M 7.66K 480M 269M 2.7亿
64 47 1.27M 626K 626K 3.86K 103M 51.2M 51.2M 64 47 1.27M 626K 626K 3.86K 103M 51.2M 51.2M
128 22 908K 250K 251K 3.71K 150M 40.3M 40.3M 128 22 908K 250K 251K 3.71K 150M 40.3M 40.3M
256 7 302K 48K 53.7K 2.27K 88.6M 17.3M 19.5M 256 7 302K 48K 53.7K 2.27K 88.6M 17.3M 19.5M
512 4 131K 7.50K 7.75K 2.74K 102M 5.62M 5.79M 512 4 131K 7.50K 7.75K 2.74K 102M 5.62M 5.79M
2K 1 2K 2K 2K 3.23K 6.47M 6.47M 6.47M 1 2K 2K 2K 2K 3.23K 6.47M 6.47M 6.47M
8K 1 128K 5K 5K 13.9K 1.74G 69.5M 69.5M 8K 1 128K 5K 5K 13.9K 1.74G 69.5M 69.5M
Total 2.63M 277G 218G 225G 3.22M 337G 263G 270G共有2.63M 277G 218G 225克3.22M 337G 263G 270G
dedup = 1.20, compress = 1.28, copies = 1.03, dedup = 1.20，压缩= 1.28，副本= 1.03，
dedup * compress / copies = 1.50 dedup *压缩/份= 1.50
Does the Server Have Enough Memory Installed to Undertake Deduplication?服务器是否有足够的内存安装进行重复数据删除呢？
The reason this question needs to be answered is that the deduplication tables consume memory and eventually spill over and consume disk space.需要回答这个问题的原因是，重复数据删除表中消耗内存，并最终溢出，占用磁盘空间。 At that point, ZFS has to perform extra read and write operations for every block of data on which deduplication is attempted.在这一点上，ZFS执行额外的每块上的重复数据删除是企图数据读取和写入操作。 This causes a reduction in performance.这会导致性能降低。
Furthermore, the cause of the performance reduction will be difficult to determine if you are unaware that deduplication is active and can have adverse effects.此外，性能降低的原因难以确定的，如果你不知道，重复数据删除是积极的，并可以产生不利影响。 A system that has large pools with small memory areas will not perform deduplication well.系统具有大池，小的内存区域不会执行重复数据删除。 Some operations, such as removing a large file system with dedup enabled, will severely decrease system performance if the system doesn"t meet the memory requirements.某些操作，如删除一个大的文件dedup dedup启用，将严重降低系统性能，如果系统不能满足对内存的要求。