topic OS block Size. in Operating System - HP-UX

OS block Size.

baiju_3 — Thu, 01 Sep 2005 09:11:52 GMT

Hi ,

Today my DBA asked me what is OS Block Size set on out HP Unix . I told I do not have any idea but showed him that filesystem block size (fstyp -v ) is set as 8KB .

Is there any thing called OS block size ?

Plz reply , thanks in advance .

Regards,
BL.

Re: OS block Size.

RAC_1 — Thu, 01 Sep 2005 09:15:35 GMT

BAIJU,
Baiju LAL

There is nothing as OS block size. All that is there is FS block size.

Which you can check as follows.
fstyp -v
df -g /dev/vgxx/lvolx

Re: OS block Size.

Marcel Boogert_1 — Thu, 01 Sep 2005 09:18:59 GMT

hi there,

You can try this to get your os block size:

fstyp -v /dev/vg00/lvol1 | grep f_bsize

Regards, MB.

Re: OS block Size.

Steven E. Protter — Thu, 01 Sep 2005 09:20:32 GMT

Block size when setting up a Volume Group has according to prior posts little or no impact on database performance.

Filesystem options can.

SEP

Re: OS block Size.

Bill Hassell — Thu, 01 Sep 2005 09:46:53 GMT

Tell your DBA that it is 8K. The reality is that HP-UX adjusts the actual I/O size according to a number of parameters. The basic blocksize on a disk (NOT a filesystem) is 512 bytes but this number is of no use to the DBA. In the old days, some Unices would run more efficiently with a specific blocksize for I/O but all of that goes out the window when you talk to arrays that hide the real disks and cache large amounts of I/O. The kernel recognizes this and looks for ways to concatenate a series of sequential I/Os, thus initiating fewer I/O's to the storage device.

Re: OS block Size.

Raj D. — Thu, 01 Sep 2005 10:03:09 GMT

Hi Lalb,

Hope the DBA might be interested knowing the disk block size , that set in the filesystem and can be used while accessing data from the FS :

check :
# fstyp -v /dev/vgxx/lvolx | grep f_bsize
and divide by 1024 , comes to KB .

Usually its 8192/1024= 8KB.

Cheers ,
Raj.

Re: OS block Size.

baiju_3 — Thu, 01 Sep 2005 12:09:09 GMT

Tnanks.