topic Re: Another RAW ?? in Operating System - Linux

Another RAW ??

MikeL_4 — Fri, 08 May 2009 17:49:21 GMT

Oracle DBA's are requesting RAW disk for there database...

can I fdisk a disk and partition part of the disk for RAW and the remainder for LVM ??

Or is the scsi_id needed for setting up raw only for the entire disk ?? or a seperate scsi_id for each partition ??

Re: Another RAW ??

Michal Kapalka (mikap) — Fri, 08 May 2009 17:57:47 GMT

Hi,

it should be a entire disk.

mikap

Re: Another RAW ??

Nido — Mon, 11 May 2009 04:56:39 GMT

Hi,

You can provide either raw slice as the whole disk or as raw partition.

If you're using LVM then create a raw logical partition and bind the volume to the raw devices using `raw` command.
check the URL: http://www.dba-oracle.com/real_application_clusters_rac_grid/raw_devices_linux.html

http://kbase.redhat.com/faq/docs/DOC-10164

Thanks,

Re: Another RAW ??

Matti_Kurkela — Mon, 11 May 2009 11:59:17 GMT

It is techically possible to give Oracle a partition or a LV to be used as a raw device, but it is not always advisable to do so.

When using a raw device, Oracle assumes it is the only one accessing that physical disk hardware, and tries to optimize its disk caching and access pattern accordingly. If other partitions/LVs are sharing the physical disk with Oracle raw data area, any access to those partitions/LVs will throw off Oracle's optimizations and your database performance may be reduced.

But if you are trying to implement a low-traffic Oracle setup (maybe a test system?) and you have a requirement to use the disk space as efficiently as possible, go ahead.

What tools are the DBAs using to configure their raw disks? With some tools, it might be easier to identify the disk with scsi_ids instead of device names. But that would be a limitation of that particular tool.

MK

Re: Another RAW ??

MikeL_4 — Mon, 11 May 2009 12:06:23 GMT

Thanks, I'll give it the full LUN....