raw partions vs file systems 
Author Message
 raw partions vs file systems

Hi,

I've only ever configured Oracle databases using Unix file systems.  A
site
I'm  starting with uses raw partitions.  Do raw partitions provide
significant performance increases?  I suppose the performance gain would
want to be
at least 10% for the additional overhead and limited flexibility of
using raw partions.

We run Oracle7/Oracle8 on Solaris 2.5.1/2.6.  As a scenario, assume a
5GB
and 10GB database.  Also, what are the differences if the database is
pre{*filter*}ly read-only as opposed to write intensive.  The
filesystems/rawpartions are striped and mirrored, although this does not

necessarily have to be the case.

Any input appreciated

Regards,
Mick



Mon, 12 Mar 2001 03:00:00 GMT
 raw partions vs file systems

I do not have numbers on FS vs Raw.

Each access to data on filesystem must interact with the filesystem overhead
(inode traversal and levels of indirection).  In a commonly accessed file,
this may not be a huge issue as this information will be cached by the OS -
which can be a problem on writes if the system goes down as data may be lost
(this is why we have fsck).

You should consider that the memory being used by the OS to cache these disk
pages might be better used if you were to instead use raw devices and
allocate that extra memory directly to the SGA.

If you are using raw devices you need not lose any sleep wondering if when
you told the filesystem to write to disk, if it really did.  The potential
lose in performance of each write to disk rather than caching in the OS can
be overcome by installing some battery backed up cache on the disk.

-Chris

Quote:

> Hi,

> I've only ever configured Oracle databases using Unix file systems.  A
> site
> I'm  starting with uses raw partitions.  Do raw partitions provide
> significant performance increases?  I suppose the performance gain would
> want to be
> at least 10% for the additional overhead and limited flexibility of
> using raw partions.

> We run Oracle7/Oracle8 on Solaris 2.5.1/2.6.  As a scenario, assume a
> 5GB
> and 10GB database.  Also, what are the differences if the database is
> pre{*filter*}ly read-only as opposed to write intensive.  The
> filesystems/rawpartions are striped and mirrored, although this does not

> necessarily have to be the case.

> Any input appreciated

> Regards,
> Mick



Thu, 15 Mar 2001 03:00:00 GMT
 raw partions vs file systems

Quote:

>Hi,

>I've only ever configured Oracle databases using Unix file systems.  A
>site
>I'm  starting with uses raw partitions.  Do raw partitions provide
>significant performance increases?

Depends on many, many factors. In general, an I/O intensive database with
multiple concurrent transactions will see more consistent, and better,
performance with raw devices. This is why Oracle (Sybase, EMC, IBM, etc.)
recommend them in such situations. The only way to really know is to
*test* - you don't seem to have that choice in this case.

Quote:
>I suppose the performance gain would
>want to be
>at least 10% for the additional overhead and limited flexibility of
>using raw partions.

You have no idea of the improvement without testing. Guessing is
meaningless. The performance might even be worse.

As regards the 'additional overhead and limited flexibility of using raw
partions', I don't understand what you mean? Get an OS with a decent LVM,
and then raw partitions are more flexible and a lot less hassle than file
systems (for which you have to mess about with raw partitions anyway). Only
'hassle' is backup. Learn 'dd' (on UNIX) or (recommended) get a backup
product that supports raw (and preferably Oracle EBU or RMAN with raw
devices) directly.

Quote:

>We run Oracle7/Oracle8 on Solaris 2.5.1/2.6.  As a scenario, assume a
>5GB
>and 10GB database.  Also, what are the differences if the database is
>pre{*filter*}ly read-only as opposed to write intensive.  The
>filesystems/rawpartions are striped and mirrored, although this does not

>necessarily have to be the case.

>Any input appreciated

Again, any reply is guesswork and utterly meaningless. Do some testing -
it's fun! :-)

Regards,

MotoX.

Quote:

>Regards,
>Mick



Fri, 16 Mar 2001 03:00:00 GMT
 
 [ 3 post ] 

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