Re: Q: Is RAID/striping good with Oracle???

R. Wayne Linton, ISP wrote:
>
> netac wrote:
> >
> > Gary Assa wrote:
> > >
> > > Would RAID and striping be a good thing with Oracle 7?

Striping is what we call RAID1.

> > > Being that tables should be on different drives from indexes, etc.,
> > > is RAID defeating the purpose? Or is it an insignificant amount
> > > balanced by the speed of RAID?
> > >
> > > I am really not up on the way RAID works.
> > > --
> > > =========================================================
>
> We use RAID-5 which is really striping at the bit/byte level across
> several volumes.

RAID 1 through 5 are all striping variations.

RAID-5 is not necessarily BIT striping ... depends upon the implementation.

Striping at the bit level is RAID3 or 4.

The implementation of RAID5 we have here is 32Mb chunks not BITs :(.

> We also use RAID-0 which is actually mirroring entire
> volumes. I have striped a tablespace across four volumes, each of which
> is mirrored and with their own access path.

This is commonly referred to as RAID0+1

> RAID-5 runs on a single controller, so your path to the data is a single one.

If RAID5 is implemented at the OS level then you could have multiple controllers but most implementations are hardware boxes with a single SCSI connection. The SCSI is usually the first thing to get overloaded.

> The advantage of striping is that you can get several paths to the data
> (presuming the volumes are on different controllers.)

RAID5 is NOT A PERFORMANCE option. RAID5 with LOTS of disk cache is ok but you hit the scsi overload problem.

RAID0+1 will give more flexibility, better performance and as good reliability.

Bruce...

--
  -----------------
   T T T T T T T T        Bruce Pihlamae
   I I I I I I I I        bpihlama_at_nla.gov.au
   I I I I I I I I        National Library of Australia
   T T T T T T T T        Phone: +616 262-1575
  -----------------       Fax:   +616 273-2116
 ===================
 "If you swallow a live frog first thing in the morning;
  nothing worse will happen to either of you that day."