The first setting is called Easy Tier acceleration. This setting is a system-wide one that is disabled by default. Turning on this setting makes Easy Tier move extents up to four times faster than when in the default setting. In accelerate mode, Easy Tier can move up to 48 GiB every 5 minutes, while in normal mode it moves up to 12 GiB. Enabling Easy Tier acceleration is advised only during periods of low system activity.

This setting can be changed online without affecting host or data availability. To turn on or off Easy Tier acceleration mode, run the following command:

SVC > chsystem -easytieracceleration <on/off>

Important: Do not leave accelerated mode on indefinitely. It is a best practice to run in accelerated mode only for a few days to weeks to enable Easy Tier to reach a steady state quickly. After the system is performing fewer migration operations, disable accelerated mode to ensure that Easy Tier does not affect system performance

IBM recommends disabling the chacha20-poly1305@openssh.com cipher (Terrapin) by upgrading to one of the versions in “Remediation/Fixes” above and then running the commands below:

versions not affected (or higher) 8.4.0.14, 8.5.0.12, 8.6.0.4, 8.6.2.1, 8.6.3.0, 8.7.0.0

From the CLI

IBM_FlashSystem:V5100-01:superuser> chsecurity -sshprotocol 4

Using the GUI (8.6.0 and higher)

Settings > Security > Security Protocol Levels and choose SSH protocol level 4 in the GUI.

Which WWN should I use to connect hosts to storage (check the host_io_permitted)

IBM_FlashSystem:V5100-01:superuser>lstargetportfc
id WWPN             WWNN             port_id owning_node_id current_node_id nportid host_io_permitted virtualized protocol
1  50050xxxx0215A04 50050xxxx0005A04 1       1                              000000  no                no          scsi
2  50050xxxx0255A04 50050xxxx0005A04 1       1                              000000  yes               yes         scsi
3  50050xxxx0295A04 50050xxxx0005A04 1       1                              000000  yes               yes         nvme
4  50050xxxx0225A04 50050xxxx0005A04 2       1                              000000  no                no          scsi
5  50050xxxx0265A04 50050xxxx0005A04 2       1                              000000  yes               yes         scsi
6  50050xxxx02A5A04 50050xxxx0005A04 2       1                              000000  yes               yes         nvme

Remove the 2 paths from disk

svctask chenclosureslot -exclude no -port 1 -slot 7 3
svctask chenclosureslot -exclude no -port 2 -slot 7 3

Then, you can mark fixed the errors present for the drives with:

svctask cheventlog -fix 2331
svctask cheventlog -fix 2337

Check now the drive status, it should reappear if not defect

lsdrive

Check also for bad blocks

IBM_Storwize:v5020:superuser>dumpallmdiskbadblocks

You can limit FC traffic to specific purpose:

• for cluster traffic (inter-node)
• for remote copy traffic (replication)

-localfcportmask port_mask
    (Optional) Indicates the Fibre Channel (FC) input/output (I/O) port mask for local system node-to-node communications only. 
    
-partnerfcportmask port_mask
    (Optional) Indicates the FC I/O port mask for partnered system-to-system communications only. Fibre Channel port mask does not affect host or storage system traffic.

To view the current port mask settings, run the lssystem command, the output shows that all system ports allow all types of traffic.

IBM_IBM FlashSystem:ITSO-FS9500:superuser>lssystem |grep mask
local_fc_port_mask 1111111111111111111111111111111111111111111111111111111111111111
partner_fc_port_mask 1111111111111111111111111111111111111111111111111111111111111111

To set the local or RPORT mask, run the chsystem command. Example shows the mask setting for a system with four FC ports on each node and that has RC relationships. Masks are applied to allow local node-to-node traffic on ports 1 and 2, and replication traffic on ports 3 and 4.

Example Setting a local port mask by running the chsystem command

IBM_IBM FlashSystem:ITSO-FS9500:superuser>chsystem -localfcportmask 0011
IBM_IBM FlashSystem:ITSO-FS9500:superuser>chsystem -partnerfcportmask 1100
IBM_IBM FlashSystem:ITSO-FS9500:superuser>lssystem |grep mask
local_fc_port_mask 0000000000000000000000000000000000000000000000000000000000000011
partner_fc_port_mask 0000000000000000000000000000000000000000000000000000000000001100

The mask is extended with zeros, and all ports that are not set in a mask have the selected type of traffic blocked.

Specify the lsportfc command to display FC I/O port IDs.