Database Reference
In-Depth Information
so for performance you should specify a storage directory for each local disk. Read per-
formance also benefits from having multiple disks for storage, because blocks will be
spread across them and concurrent reads for distinct blocks will be correspondingly
spread across disks.
TIP
For maximum performance, you should mount storage disks with the
noatime
option. This setting
means that last accessed time information is not written on file reads, which gives significant perform-
ance gains.
Finally, you should configure where the secondary namenode stores its checkpoints of the
filesystem. The
dfs.namenode.checkpoint.dir
property specifies a list of direct-
ories where the checkpoints are kept. Like the storage directories for the namenode, which
keep redundant copies of the namenode metadata, the checkpointed filesystem image is
stored in each checkpoint directory for redundancy.
Table 10-2
summarizes the important configuration properties for HDFS.
