Re: Performance difference between 2 machines

"Noons" <wizofoz2k_at_yahoo.com.au> wrote in message news:1119402457.087110.202530_at_g49g2000cwa.googlegroups.com...
> Matthias Hoys wrote:
>
>> Regarding the AIX filesystem block size : when I look at the properties
>> of
>> our enhanced journaled filesystems (JFS2), the unit size = 512 bytes and
>> the
>> filesystem block size = 4096 bytes. So what's the difference between unit
>> size and block size ?
>
> Block size is the IO size any file system IO operations will always
> use.
> The unit size is the minimal space allocation of the file system.
> Kinda similar to the old Windoze file system sector size: the minimal
> amount of space the file system will allocate to a file/inode-entry.
> In file systems with no provision for "unit size", it defaults to the
> block size.
>
>> One of our 8.1.7 DWH databases (which needs to be migrated to Oracle 10g)
>> has a block size of 16k, so what would be the reason for this ? (it was
>> installed a long time ago by an external consultant).
>
> Traditionaly, DWH consultants use a db block size of 16K.
>
>> Is there any way to estimate the optimal block size for an existing
>> database
>> ?
>
> None, other than benchmarking of your specific case.
> There are however guidelines based on past experience.
> They seem to point to 4K in AIX/JFS. But with JFS2 I'd
> probably be inclined to use 8K.
>
> But NEVER make db block size less than file system block size.
> Ie: 2K db block size on a 4K file system is a BIG no-no.
>

How could I benchmark the ideal configuration for our database ? Install different databases with different block sizes ? That's a whole lot of work, and we don't have the diskspace ... Received on Wed Jun 22 2005 - 13:58:56 CDT