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block size of vxfs after fsadm

 
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Smucker
Regular Advisor

block size of vxfs after fsadm

I have noticed on several filesystems that were extended using fsadm that the block size are not optimal

ex a former 8 gig file systems that has grown to a 32 gig file system shows 2048 as blocksize. It should be around 8192 according to fstyp.

mkfs shows:
mkfs -F vxfs -o ninode=unlimited,bsize=2048,...

fstype shows:
f_bsize: 8192
f_frsize: 2048


wouldn't this hurt performance during processing????
5 REPLIES 5
James R. Ferguson
Acclaimed Contributor

Re: block size of vxfs after fsadm

Hi:

Whether or not there is a performance penality depends (in part) on the version of JFS you are running. Things have changed between JFS 3.3 and JFS 3.5. See here for more:

http://docs.hp.com/en/5576/JFS_Tuning.pdf

However, the blocksize will be fixed from the time the filesystem was created.

Regards!

...JRF...

A. Clay Stephenson
Acclaimed Contributor

Re: block size of vxfs after fsadm

Almost certainly not. Vxfs filesystems unlike hfs (ufs) or the archaic s5 filesystems are extent-based rather than block-based. In vxfs filesystems, the blocksize only controls the smallest unit of storage that is allocated to a file and thus is more of a way to control unused space than as a performance control. I know you went to an Oracle class and they said something like "always make your db blocksize equal to the filesystem blocksize or a multiple of the filesystem blocksize" but that really doesn't apply to vxfs filesystems.
If it ain't broke, I can fix that.
Smucker
Regular Advisor

Re: block size of vxfs after fsadm

Ok then another question.

If the smallest addressable unit is based off of the bsize of the file system. Would the 32gb filesystem blocked at 2048 take more room in memory to address than the 8192.

If there is no difference then why have diffent blocksizes.

Thanks
A. Clay Stephenson
Acclaimed Contributor
Solution

Re: block size of vxfs after fsadm

This document explains it well:

http://docs.hp.com/en/B3929-90011/ch01s06.html



If it ain't broke, I can fix that.
Smucker
Regular Advisor

Re: block size of vxfs after fsadm

thanks