Re: To RAID or not to RAID ??

[newsgroups trimmed]
Sudheer Marisetti <marisett_at_bellatlantic.net> wrote:

]We are designing and building a data warehouse about the size of 40-60
]GB on Oracle 7.3.2.

 %-< %-<
]I would really appreciate if any of you could share your experiences
]with RAID-1 or RAID-5 or RAID-0+1 while building or using data
]warehouses or any database. Here is the set up we have:
]
]- HP9000/K260 Server
]- PA 8000 180 MHz processor (2 of them)
]- HP-UX 10.2
]- 384 MB memory
]- Database: Oracle 7.3.2

My experience is with Sun Solaris, Sun 1000e Server, Sun Sparc Storage Array 100 and Veritas Volume Manager.

We use a combination of RAID 5 and Striped Mirrors. People say that you either use RAID 5 or Mirrors, why not combine both? We put rollback segs and on-line redo logs on high performance mirrors, and archived logs and databases on cheaper RAID5. With the internal cacheing in the SSA, RAID 5 writes take 44ms (this is a 10Gig DB with 160 concurrent users using Mincom's MIMS3 app). We found that RAID 5 writes in an SSA were faster than the same disks in a Sun Disk Tower, which is just a box full of flat conventional disks.

Before we moved to the SSA and RAID 5 the box was definitely I/O bound, it is now CPU bound. I wounder how much of Sun/Veritas RAID 5 is realy hardware RAID?? I will be asking some others who have followed up to this, why they assume you can mix RAID levels, create some file systems with RAID5 and other striped mirrors, sharing disks and controllers, all for best performace.

One other point; I would be concerned about that 384 Meg RAM; If you don't have many users on the DB it might be enough, but it looks low to me.

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