Installation manual

Policy for Balancing Capacity
Adding a Share Farm
12-20 CLI Storage-Management Guide
Based on Latency (Bandwidth)
The NSM continuously updates its measure of the average latency (round-trip packet
time) between its ports and each share. A low latency for a share indicates high
currently-available bandwidth at the share. You can use the
balance command to
distribute new files based on latency measures instead of free-space measures. For
example, consider a share farm where one share, s1, has an average latency that is
three times faster than the latency to s2: this algorithm would send three times as
many files to s1 as s2. The share with the lowest latency gets the most new files.
To distribute more new files to shares with lower latency (and therefore more
bandwidth), use the
balance latency command:
balance latency
For example, the following command sequence configures the ‘medFm’ share farm to
distribute its new files based on the current latency at each share:
bstnA6k(gbl)# namespace medarcv
bstnA6k(gbl-ns[medarcv])# volume /rcrds
bstnA6k(gbl-ns-vol[medarcv~/rcrds])# share-farm medFm
bstnA6k(gbl-ns-vol-sfarm[medarcv~/rcrds~medFm])# balance latency
bstnA6k(gbl-ns-vol-sfarm[medarcv~/rcrds~medFm])# ...
Based on Administrative Weights
You can also choose to use the weighted-round-robin method of distributing new
files, using the weights that you set when you add each share to the share farm (as
shown in “Setting a Placement Weight for a Share” on page 12-16). This is the default
new-file-placement policy for a new share farm. The number of new files assigned to
each share is based on the weight of the share, relative to all the other share weights:
for example, if s1 has a weight of 15 and s2 has a weight of 60, s2 gets four times as
many new files as s1.
To place the new files on the shares based on their relative weights, use the
balance
round-robin
command:
balance round-robin
For example, the following command sequence causes the share farm to assign twice
as many files to the ‘back1’ share as the ‘back2’ share:
prtlndA1k(gbl)# namespace nemed