ORA-00374 - Block Size issue

Question

I've already searched and researched this quite a bit. I am not using 9i like the other post about this issue from many years ago. Before you ask "Why a db_block_size of 32k?", this is for a test case. Simple as that.
My system:
Quad DC Operton, 32GB RAM, 4x 15k SAS disks in hardware RAID10.
Windows Server 2008 R2 Standard 64bit (I much prefer Linux, but this test requires Win2008)
Oracle 11g R2 64-bit EE
The Disk with the O/S and ORACLE_HOME is formatted with the default 4k size allocation units.
The allocated database file storage IS formatted with 32k sized allocation units and is on a SAN.
I know it's 32k because when I presented the LUN to the server, I formatted it with 32k allocation units. See below the output paying attention to the * * section:
C:\Users\********************>fsutil fsinfo ntfsinfo o:
NTFS Volume Serial Number : 0x60d245e2d245bcd2
Version : 3.1
Number Sectors : 0x00000000397fc7ff
Total Clusters : 0x0000000000e5ff1f
Free Clusters : 0x0000000000e5f424
Total Reserved : 0x0000000000000000
Bytes Per Sector : 512
Bytes Per Cluster :               32768
Bytes Per FileRecord Segment : 1024
Clusters Per FileRecord Segment : 0
Mft Valid Data Length : 0x0000000000040000
Mft Start Lcn : 0x0000000000018000
Mft2 Start Lcn : 0x0000000000000001
Mft Zone Start : 0x0000000000018000
Mft Zone End : 0x0000000000019920
RM Identifier: 35506ECB-7F9E-11DF-99F3-001EC92FDE3F
So, my db file storage is formatted with a 32k allocation size.
My issue is this:
Oracle shows me the 32k block size when running DBCA using the Custom template. I choose it and the other required options are configured, and when it starts building the DB, I get this:
ORA:00374: parameter db_block_size = 32768 invalid ; must be a multiple of 512 in the range [2048..16384].
Other responses I've seen to this says "Windows doesn't support a allocation size above 8k or 16k" which is utterly absurd since I run SQL2008 on a few machines and it DOES support up to a 64k allocation size, which is what I run. I know this for a FACT.
Windows DOES support up to a 64k allocation size. Does anyone know why Oracle is giving me a hard time about it?
I saw Metalink note 794842.1, but I'd like to know the reasoning/logic for this limitation?
Edited by: user6517483 on Jun 24, 2010 9:21 PM

Answer 1

user6517483 wrote:
I saw Metalink note 794842.1, but I'd like to know the reasoning/logic for this limitation?
A WAG.. Oracle is written to be run on a wide variety of operating system. As operating systems differ one typically designs something that is equivalent in functionality to a Windows HAL - this provides an abstraction layer between the kernel services/calls that is needed by the s/w and the actual implementation of such by the kernel itself.
So despite the kernel supporting feature X, it could be different than similar features supported on other kernels and difficult to implement via this s/w HAL-like interface. The Windows kernel has a lot of differences from the Linux kernel for example.. and somehow Oracle needs to make the same core db s/w run on both. Not unrealistic to expect that some kernel features will be supported better than others, as there is a common denominator ito design and implementation in the core s/w.
As this is a case with block sizes... not that critical IMO. I have played with different block sizes in a 20+TB storage system and Oracle RAC (10.2g) on Linux (part of testing the combo of storage system and cluster and technologies used). Larger block sizes made zero difference to raw I/O performance. The impact was instead more a logical one. Fewer db blocks can be cached as these are larger.. more data can be written into a datablock. And as numerous experienced Oracle professionals have commented, Oracle decided that the default 8KB size is a best fit at this layer.
So extensive and very accurate testing needs to be done IMO to determine whether a larger block size is justified... and the effort to do that may just outweigh the little gains achieved by finding the "+perfect+" block size. Why not focus all that effort instead on correctly using Oracle? Application design? Data modeling? Development and coding? These are factors that play the most dominant roles at the end of day that impact and determine performance.