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# 1  
Old 10-16-2002
creating jfs

Need help,

I have read the docs but need some better understanding.

Can someone explain the reasons behind setting the values for
fragement size, i-node and allocation group size?

Thanks,
# 2  
Old 10-16-2002
First, let me say that my reference for this is with HPUX systems.

I am guessing that by fragment you are asking about the byte size for the segments or extents. That depends on the size of your data the default size for most systems is around 4MB. If you have very large datafiles you can set this number higher, upto 256MB or more, but for normal data you should be okay to leave it at 4MB.

Inodes represent the number of files you can create. On some systems, this number is a fixed number that is set when you create a filesystem. IF you set this number too low, you will not be able to create a file even if you have space left on the filesystem.

On systems with JFS Online, I believe that it is a variable amount that you don't have to worry about running out of inodes. You should never have to worry about it with the more advanced vxvm filesystems.

I am not sure what you mean by allocation group size. Maybe you can explain that a little more.

Smilie
Hope this helps.
# 3  
Old 10-17-2002
There's gotta be some confusion here...

On HP-UX, 4 MB is the default extent size for LVM. LVM takes a collection of physical disks and carves them up into usuable disk sections.

When you're actually using the disk sections, the LVM extent size is invisible to you. You can use these disk sections for swap areas, dump areas, raw database sections and even filesystems.

And if you wanted, you can bypass LVM and use disk directly for any of these things. If you did that, you would not even have an LVM extent size.

The Veritas filesystem also has a notion of extents but 4 MB is impossibly large for that.
# 4  
Old 10-17-2002
I was just trying to "guess" what he was talking about. I believe he was talking about the definitions of these items and not actual implementation of what you can see. Until he responds, we won't know what the impetus for the question was. Smilie


Perderabo,

Thanks for the explanation though. I enjoy your depth of knowledge on many topics on which you wax poetic. I wish I had the depth of understanding you have on many areas regarding the inner workings and behind-the-scenes machinations, history of why things are the way the are! I guess you have been doing this type of work for quite a while?

Thanks again. Smilie Smilie
# 5  
Old 10-17-2002
Thanks!! Smilie Smilie Smilie

"wax poetic"? Once in a while I have been tempted to respond in rhyme, but I've always resisted the temptation.

And, yes, I've been at this for over a year. Smilie
# 6  
Old 10-17-2002
Wait a minute... I wouldn't want to give credit improperly.

Maybe I am confusing you with: Livin"ask a question get a research paper"Free. Smilie

How long have you been involved with Linux/Unix. I thought you had been doing Admin work for a while.

I've been at it for about 6 years.

Smilie
# 7  
Old 10-17-2002
Quote:
Originally posted by Perderabo
"wax poetic"? Once in a while I have been tempted to respond in rhyme, but I've always resisted the temptation.
No!No!No!

The proper response should have been:

Quote:
Once in a while I have been tempted to respond in rhyme, but I've always resisted the temptation... Well, at least this time!
Let's get it right, people! Smilie

I return you back to your normal schedule of Unix Learnin'.
 

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