os io unit , db block size relation

Hi ,

I am trying to find the optimal size for a datawarehouse system which contains oracle , redhat linux 2.1 ,ocfs and emc , raid 10 , datawarehouse > 1tb.

My db block size is 16kb.

statfs call against the filesystems which oracle data resides returns 512 as the optimal block size.

When i create a directory in one of the ocfs file systems , its size is 32K.

sar -d reports some values in blks/s .

I want to connect all these info but i cant. Here is my questions:

1. How can i find the os io unit ? How much data does (not only in blocks , but also in bytes) the os transfer in each read ?
2. Since i use ocfs which use direct io (no os buffering) , can i say that all database ios are 16kb? (Since this is db block size) Or are all ios issued by db server 512 bytes?(Since statfs returns 512 as the optimal block size)Or are all ios issued by db server 32kb. (this is the ocfs block size)
3. I want to monitor the raid subsytem by comparing the disk io done by dbserver and os. I use v$filestat oracle table to get the number of disk reads in block , than sar -d or iostat but how can i understand what os block exactly mean in sar and iostat outputs? 16kb, 512bytes or 32kb?

Kind Regards,
hope Received on Tue Sep 14 2004 - 06:44:35 CDT