AIX and Linux

[dman7777777]

I was talking to my boss and in 6 months he said we are going to switch over to Linux. So, I am a bit confused. We run AIX boxes with AIX 5l. When he saids we are going to switch over to Linux, does this mean we are no longer going to be using the AIX 5L?

 

[Alexwhatever]

What's all this then?

AIX != free.

As far as I'm aware IBM haven't moved to a Solaris-style business model with AIX.

With regard to AIX vs. Linux - on the feature front you could argue til the cows come home. 'Linux' is just the kernel of the operating system - there are lots of different flavours of Linux distributions, each of these harnesses different 'OS features' (for want of a better term) and userspace software packages to create an OS. Collectively there's no doubt that the different Linux distros provide more features than AIX does. However, the argument lies in how much of this is mature and stable enough for deployment in an enterprise environment.

More mature and commercially-oriented distributions such as RHEL are doing a good job of making feature-rich distributions that are well tested and, most importantly, supported. However, I have no idea how the quality of RH (for example) support compares to IBM's.

The calculation that reveals which is 'better' or 'worse' would involve a metric of the maturity and stability of the software, the quality of the vendor support and the skill level and familiarity of your admins. With regard to maturity and stability, it depends on what features you want to use (esp with regard to Linux)...

There is no easy answer.

Forum - please discuss and contradict, this is an interesting subject as the RH (et al.) marketing machine steams forward and attempts to grab more and more market share from the older (and more expensive, in some ways...) 'real' UNIXes and this becomes more and more relevant to us every day...

 

[unixfreak]

You don't pay a yearly licence fee on AIX as you do on Mainframes and other system. If they have a perfectly good AIX server running, AIX won't cost them anything again.

TBH, I don't know if you pay for AIX on the original purchase order, if you do it's in the order of £300 or so (I've had to purchase it seperately before and £300 is nothing for a business), but I would have thought that if you purchase the hardware you get AIX.

Still, they already own it. And re-training people and everything else considered, "converting" their existing POWER5 to run Linux most certainly won't save them any money.

 

[spamly]

Linux has great LVM setup. Concurrent logical volumes, ext3 (enhanced journaled) filesystems, etc. Many people would argue that Linux had more LVM features than AIX until AIX 5.3. Now I would say that they are about equal. You honestly wont find a LVM feature in AIX that you won't find in Linux (yes this includes load balancing, snapshots, etc.)

AIX does come at a cost. If you want regular media updates, HACMP, VIO, micropartitioning... All these licenses cost a good bit of money at initial purchase.

There is also much more software available for Linux than for AIX. One could argue that this is not enterprise class software (vendor supported, able to run large and complex databases).

Also, you can build a Linux server on a decent intel platform for a very reasonable price. The equivalent AIX server is much more expensive. Especially if you consider the HMC console.

Now all that said, building a Linux server on P5 architecture won't save you near as much because you still need to invest in the premium IBM hardware.

 

[unixfreak]

"Linux has great LVM setup. Concurrent logical volumes, ext3 (enhanced journaled) filesystems, etc. Many people would argue that Linux had more LVM features than AIX until AIX 5.3. Now I would say that they are about equal. You honestly wont find a LVM feature in AIX that you won't find in Linux (yes this includes load balancing, snapshots, etc.)"

Excuse me?! The Linux LVM can't do anything AIX can't do. On the other hand AIX has performance stuff like lvmsar that Linux doesn't have and probably never will, and to make things worse pvmove on Linux is *still* broken and have been so for four years!

Linux has very, very basic support for controlling where on the disk to keep data and you still can't designate disk areas for LVs and hence there's no reorg VG either...

There more stuff than that I'm sure. The AIX LVM even ten years ago was far more advanced than the Linux one is today.

 

[dman7777777]

Ok my bad...now the info has changed. their keeping AIX on their main system and everything else will be linux.

 

[Alexwhatever]

unixfreak,

...won't mince words here - What's the quality of your information? Where's the experience coming from? Does this stand for the more heavyweight linux distros like RHEL?

I'm not contradicting your claims as I have no experience with LVM on Linux, but it is a little shocking if something like LVM is simply 'broken' on all Linuxes including things like RHEL.

 

[spamly]

I suppose AIX LVM finally is able to reduce the size of filesystems (with AIX 5.3). This has been available in HPUX, Veritas, and most likely Linux (since Linux LVM is based on HPUX's LVM) for at least 10 years.

You seem to be right about pvmove. It looks like it works for small filesystems, but will take forever on large filesystems. I haven't had to use it, so I've never run into that issue. I do have to admit that the pvmigrate command on AIX is fantastic. I use it to move/migrate large amounts of active data across my SAN all the time.

Some information on Linux LVM:

http://en.wikipedia.org/wiki/LVM2

http://gfs.wikidev.net/Installation

http://www.linuxconfig.org/Linux_lvm_-_Logical_Volume_Manager

We're using GFS (clusted, concurrent filesystems) and it is working well.

lvmsar is available for Linux also:

http://linux.about.com/library/cmd/blcmdl8_lvmsar.htm

From what I can tell it was available in lunix before AIX. Feel free to correct me if I'm wrong here.

lvreorg is available, but really only as a work around:

http://www.lsd.ic.unicamp.br/~oliva/snapshots/lvreorg/

I've personally discovered two major bugs with IBM's LVM over the years that have caused major outages for enterprise class applications. In both cases IBM released a patch shortly after I was effected. Both LVMs are still evolving and have issues. This is the nature of the beast.

The only issues I've had with Linux LVM is during the initial setup process. I think that is more because I'm a novice with the tools than anything else.

My point is not to say which is better. Both have their places. I currently manage three separate (relatively complex) AIX HACMP clusters which uptimes of over a year. In my opinion this is not only possible in AIX, but expected. I wouldn't expect this out of Linux - yet.

 

[unixfreak]

Alex: There's no such thing as "all Linuxes". Linux is one kernel though people are free to alter it. The LVM is from a specific company where I actually know (-ish) the head developer. Distros generally don't do anything with "Linux" itself. (With exceptions)

My knowledge comes from very extensive experience. I've worked with Linux daily for eleven years and AIX daily for 9 years and have closely followed their growth and development.

spamly: Shrinking a file system has got nothing whatsoever to do with LVM. Also, Linux didn't have LVM 10 years ago.

But yes, JFS2 is shrinkable.

pvmove isn't slow, it's broken! Won't work...

It is unclear from the links posted whether it is LVM 1 or 2 it is referring to. lvmsar and pvmove worked just fine in LVM 1 but broke/was never implemented in LVM 2.

 

[spamly]

But yes, JFS2 on aix 5.3 and above is shrinkable.

 

[unixfreak]

Maybe How often do you (need) to shrink a file system?

Also, shrinking reiser and ext3 still comes with a warning if you read the man page.