====== Host attachement using MPIO ======

===== Linux x86_64 and ppc64le =====

https://www.ibm.com/docs/en/sanvolumecontroller/8.6.x?topic=htrlos-attachment-requirements-hosts-that-are-running-linux-operating-system

You must ensure the following configuration settings to restore the path if they are lost during an upgrade or other hardware maintenance that results in a node being offline:
  * SCSI INQUIRY TIMEOUT
  * SCSI COMMAND TIMEOUT
  * Multipath settings in multipath.conf

For Redhat

To make the change permanent, edit /etc/sysconfig/grub and add to the GRUB_CMDLINE_LINUX line:
  scsi_mod.inq_timeout=70
  
Run the following command to rewrite the boot record:
  grub2-mkconfig -o /etc/grub2.cfg
  
Use the following command to change the inq_timeout parameter temporarily without rebooting:
  echo 70 > /sys/module/scsi_mod/parameters/inq_timeout
  
In RHEL6, RHEL7, RHEL8, SLES12, and SLES15 enter the following command to view that the change was made:
  systool -m scsi_mod -A inq_timeout
  
To set the SCSI COMMAND TIMEOUT

    Set the udev rules for SCSI command timeout to 120s. This is the recommended setting for all versions of Linux.

To increase the SCSI command timeout for the system, create the following udev rule: 
  # Set SCSI command timeout to 120s (default == 30 or 60) for IBM 2145 devices
  SUBSYSTEM=="block", ACTION=="change", ENV{ID_VENDOR}=="IBM",ENV{ID_MODEL}=="2145", RUN+="/bin/sh -c 'echo 120 >/sys/block/%k/device/timeout'"
  
To reload the udev rules without rebooting (or dynamically) you can run the following commands: 
  udevadm control -R
  /sbin/udevadm trigger --type=devices --action=add
 
**For Redhat 9.2 and higher**

Change the kernel parameter
  * scsi_mod.inq_timeout=70
<cli prompt='#'>
[root@rheltpl9 ~]# grubby --update-kernel=ALL --args="scsi_mod.inq_timeout=70"

[root@rheltpl9 ~]# grubby --info DEFAULT
index=0
kernel="/boot/vmlinuz-5.14.0-427.33.1.el9_4.ppc64le"
args="ro crashkernel=2G-4G:384M,4G-16G:512M,16G-64G:1G,64G-128G:2G,128G-:4G rd.lvm.lv=rootvg/root rd.lvm.lv=rootvg/swap rd.lvm.lv=rootvg/usr $tuned_params scsi_mod.inq_timeout=70"
root="/dev/mapper/rootvg-root"
initrd="/boot/initramfs-5.14.0-427.33.1.el9_4.ppc64le.img $tuned_initrd"
title="Red Hat Enterprise Linux (5.14.0-427.33.1.el9_4.ppc64le) 9.4 (Plow)"
id="c4ba590dff44403bb6ce4ee53e233ca8-5.14.0-427.33.1.el9_4.ppc64le"

[root@rheltpl9 ~]# cat /etc/default/grub
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT="ofconsole"
GRUB_CMDLINE_LINUX="crashkernel=2G-4G:384M,4G-16G:512M,16G-64G:1G,64G-128G:2G,128G-:4G rd.lvm.lv=rootvg/root rd.lvm.lv=rootvg/swap rd.lvm.lv=rootvg/usr scsi_mod.inq_timeout=70"
GRUB_DISABLE_RECOVERY="true"
GRUB_ENABLE_BLSCFG=true
GRUB_TERMINFO="terminfo -g 80x24 console"
GRUB_DISABLE_OS_PROBER=true
[root@rheltpl9 ~]# init 6
</cli>

Check after reboot
<cli prompt='#'>
[root@rheltpl9 ~]#  systool -m scsi_mod -A inq_timeout
Module = "scsi_mod"

    inq_timeout         = "70"
[root@rheltpl9 ~]# cat /sys/module/scsi_mod/parameters/inq_timeout
70
</cli>

===== Windows =====

Changing the disk timeout on Microsoft Windows Server

On your Windows Server hosts, change the disk I/O timeout value to 60 in the Windows registry, as follows:

    In Windows, click Start > Run.
    In the dialog text box, type regedit and click Enter.
    In the registry browsing tool, locate the HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Disk\TimeOutValue key.
    Confirm that the value for the key is 60 (decimal value). If necessary, change the value to 60.