INFORMIX on HP UX 11.11

[patrick coutinho]

Hi,

I am faced with a new challenge. that of setting up an HP UX 11.11 server for an Informix database. this is for an application called METRICA. I think its for switch traffic analysis in our telco.

Could not understand too much of the consultants notes on Informix. Something about Raw informix Disk Requirement.

Am attaching, a brief extract from the document. Anyone out there with some info to help me, i would be gratefull.

Thanks in advance,

Patrick

[A. Clay Stephenson]

What they are telling you is that they want disk space that is treated as simply a device. e.g. /dev/rdsk/c1t6d3 and they want them split into 2GB chunks. This means that you will have over 200 raw disk device nodes and that sounds like a nightmare to me.

Raw io means that there is no filesystem associated with this disk space so that the entire device chunk is simply treated as a chunk of disk blocks.

After reading the attachment, their goal is to bypass the UNIX buffer cache. Another way to accomplish the same thing is to use the OnlineJFS vxfs mount options convosync=direct,mincache=direct. That will bypass the buffer cache but let you use conventional cooked files. I would certainly do this in preference to over 200 raw devices.

[Pete Randall · Accepted solution]

Patrick,

I can give you a brief outline of what you need to do, then you can ask further questions.

Informix requires disk space in what it calls chunks, which are 2GB each in size. What you do is set up a Volume Group (man vgcreate) with enough physical disks in it to satisfy your total space requirement. The the Volume Group is broken down into Logical Volumes (man lvcreate) that are each 2GB in size. Then the raw logical volume is used to create a chunk. This is accomplished by placing a link under the /dev/vgNN directory that points the chunk to the raw logical volume:
lrwxrwxr-x 1 root sys 17 Jul 13 2002 o001.chk -> /dev/vg002/rlvol01

and so on for all your chunks.

Does that help?


Pete

[patrick coutinho]

Thanks very much Clay. let me understand. Are u saying that i take the disk device presented form my EVA and create a volume group and a logical volume. then what do i do. do i have to create just one JFS file system with the mount options u have given. Also i do not have the Online JFS license. Is that a problem.

I would highly appreciate if u could walk me thru the required stepsm, as i am a little new to HP UX.

Many Thanks in advance

Patrick

[patrick coutinho]

Thanks very much Pete, but creating so many logical volumes and then links seems pretty horrenous. Any easier way to go about this.

[Doug Burton]

Hi Patrick,

It's been a while but I remember Informix wanting raw disk space as well. However, I heard (read: not confirmed), that the latest and greatest Informix version, whatever that is, will use a mounted and larger than 2g filesystem. Are you using the latest version?

Raw disk space was a pain to "watch" from what I remember. We had to monitor disk space using Informix. The DBA managed it. Couldn't use "bdf".

If your stuck using the nasty raw 2g limits then you might want to look into scripting the creation of the devices and links.

[Pete Randall]

Patrick,

Unfortunately, Informix is still stuck in the dark ages and can only deal with 2GB chunks. That's the way it is and that's what you'll have to deal with.


Pete

[Pete Randall]

Patrick,

And . . . it's actually not that onerous a task. You create the VG as usual and then you can you use a simple for loop in a script to create the LV's and the links to them!


Pete

[A. Clay Stephenson]

If this were me, I would setup a large LUN or two on your array and then use raw Logical volumes as your raw disk but before I did that I would find out if your version will support "cooked" files and use them instead with the above mentioned vxfs mount options. OnlineJFS is not free but it is one of those things that no serious HP-UX should be without. It's useful for so many other things. If you use the mount options, my experience with Oracle has been that the performance is all but indistinuishable from that of raw disk although the newer versions of Oracle and HP-UX typically now perform best with fully cooked files using the buffer cache. A lot can be said for being able to use standard tools to view disk space and for backup. Informix has its own backup tool but the only standard tool for backing up raw devices is dd and that really can't be considered a robust option.

There is one exception where I would NOT used cooked files with or without buffer cache and that is multiple servers sharing common data space. There you want raw i/o although Veritas makes a filesystem that handles this as well but I would have to be really convinced to trust it.

[patrick coutinho]

Thank Your very much everyone. Since i do not have OnlineJFS, i think i will have to go with Pete's suggestion. A script will do the trick.

Just one quesition Clay, on the topic of OnlineJFS. I heard that it is licensed per processor and is expensive. DO u have any link that will give more info on the advantages of onlineJFS to enable me to present this to our management.

Thanks & Regards,

Patrick

[A. Clay Stephenson]

Well, I'm not gonna do marketing for HP but here is a reference:
http://www.hp.com/products1/unix/operating/filesystems.html

OnlineJFS makes it possible to grow filesystems "on the fly" in addition to enabling extra mount options. It also makes snapshot mounts possible. In combination with MirrorUX, OnlineJFS is really the first tier to highly available systems.

Using OnlineJFS and MirrorUX, I honestly can't remember the last time I had to shutdown for disk replacement/maintenance but at the very least, it's been years. I have nearly reached the 5 year mark with zero unplanned production downtime.

[patrick coutinho]

Thanks Clay,

Your feedback is valuable.

Regards

Patrick