[Ocfs2-users] Filesystem Block Size w// DB_BLOCK_SIZE

[Luis Freitas]

Karim,

  This is not OCFS2 related, it is more related to the disk hardware capabilities and how it works.

  That will depend on your OS, HBAs and storage, and the workload.

  There is a maximum queue depth associated with each LUN, so if you use several LUNs on the same device, you could achieve more outstanding scsi commands open on the controller. But each port will also have a maximum queue depth that cannot be excedeed, so at some point using extra LUNs wont give you this advantage.

  If the storage/disk have more outstanding requests it could provide a better performance by reordering them to provide a larger overall throughput, given that the storage hardware supports this. Probably it supports it, since even low end SATA disks supports reordering nowadays.

  On the other hand the database (Or ASM for that matter) has no ideia that these luns are from the same device, so it will spread the data evenly accross them, and your data will end up scattered accross the disk, instead of concentrated at the start of the disks. This will bring a performance penalty, most noticeable on full table scan operations since they read the data sequentially from the start to the end. If you tune the tables extent size you can work around this problem.

Regards,
Luis

 


--- On Thu, 12/18/08, Karim Alkhayer <kkhayer at gmail.com> wrote:

> From: Karim Alkhayer <kkhayer at gmail.com>
> Subject: [Ocfs2-users] Filesystem Block Size w// DB_BLOCK_SIZE
> To: ocfs2-users at oss.oracle.com
> Date: Thursday, December 18, 2008, 9:20 PM
> Hello All,
> 
>  
> 
> We're hosting DB1 and DB2  with db_block_size  set to 
> 8K, 16K respectively
> 
>  
> 
> File system creation is done with mkfs.ocfs2 -b 4K -C 32K
> -N 4 -L   LABLE
> /dev/mapper/xxxx
> 
> Mount is done with:  ocfs2  _netdev,datavolume,nointr 0 0
> 
>  
> 
> I'd like to know if we can separate most of the
> tablespaces on different
> LUNs, even if they're on the same disk group sometimes,
> is it possible to
> gain better performance? Is the impact limited to the time
> of creating the
> tablespaces only (assuming they're pre-sized properly)?
> 
>  
> 
> Current OCFS2 version is 1.2.1
> 
>  
> 
> Current OCFS2 components:
> 
> ocfs2-tools-1.1.4-0.5
> 
> ocfs2console-1.1.4-0.5
> 
>  
> 
> # uname -r
> 
> Kernel 2.6.5-7.257-default
> 
>  
> 
> # cat /etc/SuSE-release
> 
> SUSE LINUX Enterprise Server 9 (ia64) VERSION = 9
> PATCHLEVEL = 3
> 
>  
> 
> Oracle 10.1.0.5
> 
>  
> 
> Appreciate your input 
> 
>  
> 
> Best regards,
> 
> Karim
> 
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