Just say you change the queue_depth on a hdisk with chdev –P . This updates the devices ODM information only, not its running configuration. The new value will take effect next time I reboot the system. So now I have a different queue_depth in the ODM compared to the devices current running config (in the kernel).   What if I forget that I’ve made this change to the ODM and forget to reboot the system for many months? Someone complains of an I/O performance issue....I check the queue_depths and find they appear to be set appropriately... [More]

Tags:  lsattr chris 7.1 chdev queue_depth odm aix -p kdb gibson 6.1

When attempting to change the max_transfer attribute on a VSCSI hdisk, the following error was displayed:   # chdev -l hdisk0 -a max_transfer= 0x100000 -P Method error (/etc/methods/chgdisk):         0514-018 The values specified for the following attributes                  are not valid:      max_transfer     Maximum TRANSFER Size   The desired value, 0x100000, was an allowed value for this type of device (as shown in the lsattr output below):   # lsattr -El hdisk0 PCM             PCM/friend/vscsi                 Path Control... [More]

Tags:  rmdev vtopt0 max_transfer rmvdev aix vios chdev hdisk cd0 virtual_optical vio

Here are some questions I received recently regarding VLAN tagging on the VIO server. My answers are shown in green .   “Hi Chris,   Q: I’m trying to understand when, where and why there would be the need to use ‘mkvdev –vlan (etc.) on the VIOS, and I’m wondering whether you would be able to clarify this for me, please.   Is it necessary to add the VLAN tag devices to the SEA, or is it suffice to just have them defined within the Virtual Ethernet itself which is part of the SEA?”   A: It is suffice to simply define the VLAN ids assigned... [More]

Tags:  tagging ent6 sea virt_adapters=ent3 vlan power7 hmc tag -attr mkvdev ent5 -dev -vlan chdev dynamic dlpar

This entry is similar in theme to one of my previous posts about verifying your hdisk queue_depth settings with kdb . This time we want to check if an attribute for a Virtual FC (VFC) adapter has been modified and whether or not AIX has been restarted since the change. The attribute I’m interested in is num_cmd_elems . This value is often changed from its default settings, in AIX environments, to improve I/O performance on SAN attached storage.   From kdb you can identify the VFC adapters configured on an AIX system using the vfcs... [More]

Tags:  -p odm kdb lsattr chris_gibson num_cmd_elems adapter vfcs aix chdev reboot vfc

Are you backing up your AIX systems over Virtual Ethernet adapters? Of course you are, who isn’t right? Are your backup server and clients on the same physical POWER system? You are most likely backing up over Virtual Ethernet to another AIX LPAR that is running your enterprise backup software, such as TSM or Legato Networker for example. And you probably have a dedicated private virtual network (and adapters) on both the clients and the server to handle the traffic for the nightly backups. The next question is, have you tuned your... [More]

Tags:  min_buf_huge=96 backup netstat slow hypervisor -a aix max_buf_huge=128 tsm chris_gibson min_buf_large=96 max_buf_large=256 networker min_buf_medium=512 -l adapter max_buf_medium=1024 virtual ent1 chdev –a ethernet