topic Re: Max root size in Operating System - HP-UX

Max root size

Nick_135 — Mon, 26 Jan 2004 13:28:16 GMT

I know that the maximum size for root is either 2GB or 4GB depending on the processor. My question is why is there this limit and also what symptoms might I see if root was larger than this limit? I believe that some of our sys-ads have been violating this.

Is there any documentation on this subject? I have only found a couple of sentences on docs.hp.com.

Re: Max root size

Jeff Schussele — Mon, 26 Jan 2004 13:36:07 GMT

Hi Nick,

I know of no "hard-set" limit for root size. Just the overall disk size would be a limit.
The rule I'm most aware of is that /stand, / & swap must be contigous. But I don't see any reason why you couldn't have a 32 GB / on a 73 GB boot disk. Now I *could* see many reasons why you wouldn't want a huge / FS size...

Rgds,
Jeff

Re: Max root size

Pete Randall — Mon, 26 Jan 2004 13:38:57 GMT

I must agree with Jeff - I've never heard of any such limitation. Considering the fact that the smallest disk you can buy nowdays is 36GB, what would one do with the remaining 32GB? It would be wasted.

Pete

Re: Max root size

Sridhar Bhaskarla — Mon, 26 Jan 2004 13:43:48 GMT

Hi,

I echo the others. I haven't heard about this limit based on the processor.

Usually SAs do not create bigger / filesystems as it may lure them in future to create directories for applications and end up filling up the space.

-Sri

Re: Max root size

Nick_135 — Mon, 26 Jan 2004 14:24:31 GMT

Now I am confused.

From "Managing Systems and Workgroups":

"As of 10.10, the maximum size of HFS
and JFS (VxFS) file systems increased from 4GB to 128GB. However,
your root or boot logical volume is limited to either 2GB or 4GB,
depending on your processor."

The 2GB or 4GB was dependent on whether you are running a 32 or 64 bit OS.

We actually have been running with this limit since the 9.0 days.

What is my error here?

Re: Max root size

Jeff Schussele — Mon, 26 Jan 2004 14:37:26 GMT

Hi (again) Nick,

That must be an old guide. AT 11.X for sure & maybe even at 10.3, I believe that restriction went away.

I looked at the current guide - here:

http://www.docs.hp.com/cgi-bin/fsearch/framedisplay?top=/hpux/onlinedocs/B2355-90742/B2355-90742_top.html&con=/hpux/onlinedocs/B2355-90742/00/00/1-con.html&toc=/hpux/onlinedocs/B2355-90742/00/00/1-toc.html&searchterms=Systems%7cWorkgroups%7cManaging&queryid=20040126-123157

And cannot find that note anymore.

Rgds,
Jeff

Re: Max root size

Robert-Jan Goossens — Mon, 26 Jan 2004 14:43:03 GMT

Nick,

Check this doc,

Document description: Maximum IODC addressable range for dump and swap volumes
Document id: KBRC00012827

Europe
http://www4.itrc.hp.com/service/cki/docDisplay.do?docLocale=en_US&docId=200000069279329
US
http://www2.itrc.hp.com/service/cki/docDisplay.do?docLocale=en_US&docId=200000069279329

Regards,
Robert-Jan

Re: Max root size

Jeff Schussele — Mon, 26 Jan 2004 14:44:40 GMT

Back at HP-UX 10.01 the max supported HFS and JFS filesystem size was 4Gb & max file size was 2Gb. But since 10.2 that's kept going up.
So that was *definitely* the limit for 10.01, but since 10.2 that restriction is not in place.

Here's a link to max file & filesystem sizes for various OS versions:

http://docs.hp.com/hpux/onlinedocs/5971-2383/5971-2383.html

Rgds,
Jeff

Re: Max root size

Bill Hassell — Mon, 26 Jan 2004 14:44:54 GMT

The older HP computers (late 80's and early 90's) had Processor Dependent Code (PDC) that could not address anything larger than 2Gb. Thus, if you created very large lvol1 and lvol2, the PDC ROMs would mistakenly roll-over, especially when the swap area and dump area were shared. The symptom was that a system crash would completely wipe out the boot area as well as the first filesystem on the disk. This happened as the PDC ROMs would start writing to the dump area, then rollover to zero as the address of the dump area went larger than 2Gb. Back then, a 1Gb disk was really big so when 4Gb disks came out, there were a layouts and preset partitions in 9.04 and earlier.

The docs will be very hard to find as all of the hardware with these limits has been obsolete for many years. As far as I can remember, all CIO boxes had this limit (815,825,835,845,855,865), Emerald class (860,870), probably the T500/T600 and perhaps even the E25,E35,E45,E55. The D-class is fuzzy as it came out while 4Gb disks were commonly available. I believe that K-class is safe (but keep the firmware up to date) and all PA-8000 (aka, 64-bit capable) processors and higher are clean. number of problems with older boxes. There were similar problems with whole-disk Early 700-series workstations (715,725,735,etc) probably had similar limitations.

Keep in mind that these are physical disk limits. The PDC doesn't know anything about logical volumes as it simply has a start addtress given to it for boot or dump. As far as root (the / filesystem), this should always be about 130 to 230 megs in size and is static (does not grow). If it does, something has gone wrong, typically bad installation software that creates directories without asking.

Re: Max root size

Nick_135 — Mon, 26 Jan 2004 14:48:09 GMT

I pulled that quote off of edition 6 on doc.hp.com this morning. I found the blurb on page 339 on the link in your reply. Does it make any sense?

Re: Max root size

Jeff Schussele — Mon, 26 Jan 2004 14:53:36 GMT

Ok - I see it now. Boy they really buried it...

Think that's just legacy text in there. Note that it dates to 10.10 which is ancient.

Still fairly certain that it's not a limit anymore.

But again as I stated earlier and as Sri & Bill also pointed out, you really don't want one that big anyway. We make ours either 256 or 512 MB & it works fine for us.

Rgds,
Jeff

Re: Max root size

Nick_135 — Mon, 26 Jan 2004 15:51:39 GMT

We distribute our software to our customers with a stripped down version of 11i. Our customers typically do not have a great deal of knowledge on HPUX installs. Because we are unable to know the configuration of all of our customers workstations, our install script creates three basic lvols (/stand, swap, & root). Everything therefore is lumped into root. Root has stayed at 4GB because of this so called limitation.

Re: Max root size

Jeff Schussele — Mon, 26 Jan 2004 15:57:06 GMT

Nothing inherently *wrong* with that other than 4GB is really "tight" for an 11i install. In fact that's the absolute minimum recommended by HP for 11.11. But that's for the entire vg00 VG.
So you're saying that /usr, /var, /opt, /tmp, /home are not all separate filesystems? They're all just dirs in /?

Rgds,
Jeff

Re: Max root size

Nick_135 — Mon, 26 Jan 2004 16:27:22 GMT

Yep, that's what I am saying. Sounds crazy, I know. I do not agree with it, but that is how it was decided several years ago before I worked here. Like I said, our install is really stripped down. The OS is only around 1.66GB.

Thanks for all the help,

Nick

Re: Max root size

Bill Hassell — Mon, 26 Jan 2004 16:34:18 GMT

This is fairly common in the workstation world (root or / is one giant partition). Since workstations are generally single seat boxes (one user), then the problems associated with /var filling up, etc are limited to just the one user. Actually, there are still some admins that install and run without LVM, just whole disks. However, from experience, I can tell you that this is a nightmare for Ignite/UX and getting things restored...it is very non-standard.

So with a recent piece of hardware (PA-8000 processor or better, which means 64bit capable) you can install an 18Gb or even a 36Gb drive and create (gulp!) a 36Gb root filesystem. Most server admins will see the PC-ness of this design. As long as you provide some method to manage disk space, all is well. Or you could use the ostrich approach: ignore the problem and if the disk fills up, reinstall.

Re: Max root size

Nick_135 — Mon, 26 Jan 2004 16:50:11 GMT

That is why we do it. I thought there was a limitation to root because of what I read in the above document. When we did need more space, then we would create another lvol with the unused space on the disk. I would rather change our script to increase root right from the install. Like I said, I do not want a huge root volume either, but it is easier for our customers to manage.

Thanks,
Nick