Re: Raid5 Vs Raid0+1 -- Raw Vs Solaris 9 Concurrent Direct IO UFS

  • From: Paul Drake <discgolfdba@xxxxxxxxx>
  • To: oracle-l@xxxxxxxxxxxxx
  • Date: Thu, 26 Aug 2004 00:22:51 -0700 (PDT)

--- Deen Dayal <deen.dayal@xxxxxxxxxxxxxxx> wrote:

> We are planning to move our current database to new
> Hardware Sun 12k +
> Hitachi SE 9970. 
> Our current database runs on Sun A5000 array with
> Raid0+1 on raw devices.
> Sun engineer who is here at our site for
> implementation of Hitachi SE9970
> suggests that we should go Raid5 ( 3 + 1P ) in the
> parity group as RAID5
> gives better read performance than raid0+1 and any
> writes are going to the
> cache any way, so we should not be worried about
> write performance. There is
> 16GB cache on the Hitachi. 

That salesperson made their quota right there.
Their golf pro should be sending you a fruit/cheese

> Database is going to be striped across 10 parity
> groups and each parity group consists of 4 physical
> disks.

no wonder my !@#$%^ nj taxes are so damned high.

4 drive raid 5 volume?
ask him to do the math.
ask him what you optimal db_file_multiblock_read_count
should be.

if he would have said 5 drive RAID 5 volume, I would
have at least listened further.

does he have the slightest clue as to _your_
application's block size (e.g. db_block_size).

the SA was assimilated.
hopefully, the vendor took him out on a most enjoyable
venture to a city such as Montreal. 
One full of culture.

beware of a small, slimy creature with large teeth
tearing open his abdominal wall (from the inside) to
escape to gestate into an 8 foot tall, mean, human
chewing alien.

As with database re-orgs, new hard drives that are say
Ultra 320 SCSI (320 MB/sec interface), replacing
existing U2W SCSI (80 MB/sec interface) - where the
new, sexier models outperform the older, more reliable
but closer to MTTF, 4 year old models, masks the true

At least you aren't comparing apples.



check out the paper at on "aligning
database block and stripe size boundaries".
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