I am using NAS replication and I am getting very slow write performance. My RAID is set to cache enabled.
You have 5 active snapshots assigned to one LV, which can affect performance. Solution:
Reduce the number of snapshots you have assigned to a single LV.
NOTE: If the amount of RAM in your system is minimal, i.e., 2GB, you may need to add more. Snapshots require more resources to function and will use more RAM than a simple replication task.
The snapshot function enables the system administrator to freeze the data at a certain time. From this moment on, the users work on a virtual data volume and all changes to the volume are stored in a different partition.
After each change to the data, the original version is copied to the snapshot. When the snapshot task is stopped, the data stored directly on the snapshot is lost.
Under normal conditions, an active snapshot slows down writing to the disk, because the original data is moved first to the snapshot before the original is replaced with the new data.
Ref: Ticket #1004677