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Script to Display FC Queue Depth Settings

AnthonyEnglish Comment (1) Visits (2051)

My compatriot Chris Gibson highlighted a great performance tuning attribute for Fibre Channel adapters in this blog post . I was so excited that I dusted off my blog-writing skills (much neglected) and got fired up enough to put Chris' advice into practice via a script. First, the advice - which came originally from IBM's Dan Braden - is to display the number of command elements - num_cmd_elems - on a Fibre Channel adapter. num_cmd_elems? Huh? On AIX (and on the Virtual I/O Server) there is an attribute on... [More]

Identificações: fc dan chris gibson aix fibre channel chdev queue adapter num_cmd_elems technote depth performance disk braden

Clean up virtual SCSI disks without an outage

AnthonyEnglish Comments (4) Visits (7477)

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]

Identificações: vscsi disk virtual_scsi bios

UPDATE: Hoarders and chuckers (Reconstructing a VG)

AnthonyEnglish Comments (4) Visits (4097)

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]

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

Examine hdisk LV layout with readvgda

AnthonyEnglish Comments (2) Visits (9226)

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]

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

%iowait "A misleading indicator of I/O performance"

AnthonyEnglish Visits (8767)

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. 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 performance Performance monitoring tools Tuning, including queue depth... [More]

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

What Winnie-the-Pooh learned about Production upgrades

AnthonyEnglish Visits (2292)

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]

Identificações: backup growth capacity production storage disk disaster_recovery planning dr

Show disk size with getconf DISK_SIZE /dev/hdisk0

AnthonyEnglish Comments (6) Visits (31814)

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 the Latin verb deprecare,... [More]

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

topas reports disk busy 0.0%

AnthonyEnglish Visits (5493)

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,... [More]

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

Migrating data with mklvcopy

AnthonyEnglish Comments (3) Visits (8763)

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]

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

UPDATED: topas features: column sort, toggle to nmon and more!

AnthonyEnglish Comment (1) Visits (7631)

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]

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

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