topic Re: How to find OS block Size in Operating System - HP-UX

How to find OS block Size

Sushil Singh_1 — Thu, 23 Oct 2003 15:02:00 GMT

Hi All,
Trying to create database on HP-UX. It been long I worked on HP. I needed to know how to find the Operating System Block Size and can I increase or decrease it as needed ?

Thanks you all
Sushil

Re: How to find OS block Size

Brian Bergstrand — Thu, 23 Oct 2003 15:08:53 GMT

Depends on the filesystem. HFS uses an 8K block by default, and JFS uses a 1K block (but allocates in multiple blocks called extents).

Using 'fstyp -v' on the filesystem device will give some superblock info that contains the block size.

eg:

fstype /dev/vg00/lvol1

HTH.

Re: How to find OS block Size

James A. Donovan — Thu, 23 Oct 2003 15:10:41 GMT

fstyp -v /dev/vgXX/lvolY

f_bsize will show you the block size of the filesystem in bytes. To change the block size would require rebuilding the filesystem.

Re: How to find OS block Size

Jeff Schussele — Thu, 23 Oct 2003 15:12:33 GMT

Hi Sushil,

If you mean disk block size, the default is 1K. But this *could* be overriden with the -b parm of the mkfs command at FS creation time.

Rgds,
Jeff

Re: How to find OS block Size

prasad_15 — Thu, 23 Oct 2003 15:13:24 GMT

It might help

http://forums1.itrc.hp.com/service/forums/parseCurl.do?CURL=%2Fcm%2FQuestionAnswer%2F1%2C%2C0xee0bcb60e503d6118ff40090279cd0f9%2C00.html&admit=716493758+1066939901488+28353475

Re: How to find OS block Size

prasad_15 — Thu, 23 Oct 2003 15:14:59 GMT

df -g

Re: How to find OS block Size

Jeff Schussele — Thu, 23 Oct 2003 15:23:09 GMT

Let me refine that answer - defaults are as follows:

FS size < 8GB = 1024
FS size > 8 & < 16 = 2048
FS size > 16 & < 32 = 4096
FS size > 32 GB = 8192

But again this can be overriden.

Rgds,
Jeff

Re: How to find OS block Size

A. Clay Stephenson — Thu, 23 Oct 2003 18:01:00 GMT

Surprisingly, if you are using vxfs filesystems (and you certainly should be), and in spite of what has been beaten into your head by Oracle, filesystem block size does not matter. Vxfs filesystems are extent-based, so that unlike hfs filesystems, it really doesn't matter. Things like LVOL stripe size matter much more and for that 64K is a rather good value for LVOL's which host vxfs filesystems.

Re: How to find OS block Size

Con O'Kelly — Thu, 23 Oct 2003 20:01:51 GMT

Hi Sushil

I'd point out that if you use fstyp -v to determine block size you need to look at the 'f_frsize' parameter not as you would assume 'f_bsize' parameter. The f_bsize parameter doesn't report the correct block size.

You can also use the following command:
# mkfs -m
(eg mkfs -m /dev/vg01/lvol3)
This will show you all the parameters used to create the filesystem including block size (look for bsize value which is in bytes).

Also have a look at the JFS Fileyststem Admin Guide:
http://docs.hp.com/hpux/pdf/B3929-90011.pdf

Cheers
Con

Re: How to find OS block Size

Con O'Kelly — Thu, 23 Oct 2003 23:10:11 GMT

Hi (again)

I found a thread to confirm what I said in the previous post about fstyp -v command:
http://forums1.itrc.hp.com/service/forums/parseCurl.do?CURL=%2Fcm%2FQuestionAnswer%2F1%2C%2C0x22307b8d1de3d5118ff40090279cd0f9%2C00.html&admit=716493758+1066968007792+28353475

To summarise:
For vxfs filesystems the 'f_bsize' parameter shows the maximum block size, while the 'f_frsize' parameter shows the actual block size.

Cheers
Con