If you are using virtual SCSI (VSCSI) disks, you may occasionally find you need to reclaim them. (Shocking as it may seem, sometimes people actually do give back disk they have requested for some temporary project). Here's how to reclaim a VSCSI disk and its associated SAN LUN. Ordinarily, there should be no need for a reboot, either of the AIX logical partition or the Virtual I/O Server.   I'm giving a sort-of high level view, skipping the SAN allocation details.   Switching into reverse     Removing a VSCSI disk (and its LUN) is just the... [More]

Marcações:  vscsi disk virtual_scsi bios

It's pretty easy to move a volume group from one AIX system to another. You unmount all the file systems from the source volume group, varyoff the VG, export the volume group ( exportvg ), and then remove the disks from the source system ( rmdev -dl hdisk N ). Then you assign the LUNs to the target host, import the volume group , mount the file systems, and check permissions. But what if you want to copy  a volume group? You might want to replicate a volume group, by doing a flash copy across the SAN. Then on the remote site, you'd present the... [More]

Marcações:  physical_volume varyoffvg recreatevg varyonvg migration volume_group importvg pv file_system disk exportvg aix lun flash_copy

JUDGING A DISK BY ITS COVER When you have an hdisk and are wonderig what it might be used for, you can use the readvgda command. This displays all sorts of helpful infomation about the Volume Group Descriptor Area (VGDA) which is on every hdisk that belongs to a volume group. It's the sort of information you'd expect to get from the LVM commands such as lslv and lspv , with this difference: the volume group doesn't need to be varied on for you to inspect its VGDA. You can even run readvgda on the VIO server to see what logical volumes are... [More]

Marcações:  volume_group_descriptor aix lslv lun lspv disk hdisk volume vgda lvm pp_size group lsvg readvgda

At the IBM Power Systems Technical University in October, there was a fascinating session on Disk IO Tuning in AIX 6.1.  I didn't get to see the session, but the presentation slides are well worth reading. (URL to the slides updated, Jan 24, 2017). Even if you're not running 6.1, the principles and examples will be relevant. The session had Dan Braden as its author and was presented by Steve Nasypany, and it covered topics such as:   The importance of I/O tuning Disk basics and performance overview How to improve disk... [More]

Marcações:  mount aix chlv chfs log=null ram_disk tuning nmon io no_logging disk topas performance iowait iostat rmfs power_systems queue_depth

The Production ripple effect What is it about Production systems? They so dominate the landscape that people can forget that there are non-prod systems which may have even more of an impact when they are tinkered with or left to wither. Whether it comes to monitoring, backups, or DR, somehow we can forget that an upgrade to prod can have a ripple effect throughout the whole landscape, even if the upgrade is implemented without a hitch. Honey and condensed milk Think of one example: changing the disk architecture for a production system. Growth... [More]

Marcações:  backup growth production capacity storage disaster_recovery disk planning dr

Give bootinfo the boot If you want to get the size of a disk (virtual or physical), you can use the AIX getconf command .   getconf DISK_SIZE /dev/hdisk0 140013     The size is reported in MB, so the disk above is a 140 GB disk. You could use the bootinfo -s, but that command is  deprecated!   so I'm not even going to give you a link to its man pages. Maybe you're not exactly sure what "deprecated" means, but it sounds bad, doesn't it? According to Wikipedia , "deprecated" derives from... [More]

Marcações:  mb size lsdev lspv volume_group getconf aix gb deprecated disk "lspv_size" vios bootinfo san physical lun

HOT DISKS TRYING TO LOOK COOOOOL  Have you ever noticed a system where the users are reporting slow response times, but topas -D (or pressing D from within the topas main screen) shows the Disk Busy is constantly 0.0%, even on disks with high I/O? Suspicious, isn't it? Let's try iostat -d: System configuration: lcpu=4 drives=7 paths=14 vdisks=2                 " Disk history since boot not available. " Aha! What's going on? The iostat command documentation explains Disk Input/Output History To improve performance, the collection... [More]

Marcações:  aix disk hot_disk statistics lsattr user_based_alerting busy chdev topas iostat high_io performance smit

SERVING UP LVs, PVs and PAVs Since we've got redundant arrays on SANs these days, it may seem almost quaint to speak about software mirroring using the AIX Logical Volume Manager. Even so, LVM is very useful when you want to move data around. If you need to move to a new storage subsystem or just to a new LUN, and you're not able to do it on the backend, the LVM may be just the ticket. For example, supposing you are using a LUN that's a whole lot bigger than you need. There might be a lot of reasons how it came to that but the most common one... [More]

Marcações:  syncvg san lvm disk synchronise varyonvg logical_volume_manager reducevg mirrrovg storage extendvg lv aix mirror smit unmirrorvg pavlova migratepv lslv mklvcopy lun lsvg smitty vg logical_volume rmlvcopy volume_group

topas and nmon - what a performance! UPDATE: I'm grateful to Chris Gibson for highlighting some great new features available in topas for AIX 7.1 and AIX 6.1 TL 6: freeze the screen using the spacebar (spacebar melts your screen again) page up and page down to view several pages of data. See the comments for more details. The topas command is a very popular tool for checking performance of an AIX system. Another highly popular one is nmon (Nigel's monitor, so named because it was written by Nigel Griffiths, the man behind most of the excellent... [More]

Marcações:  ctos aix7 6.1 7.1 sar toggle disk tools aix6 iostat performance aix monitoring topas memory nmon