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Re: [Q]: Raid 0 or Raid 5 for DATA tablespaces : Which is best ?

From: George Dau <gedau_at_mim.com.au>
Date: 1997/08/12
Message-ID: <33f5c3d5.1913233263@isafin1>#1/1

Jerome Grandjanny <grandjanny_at_ldg.bruyeres.cea.fr> wrote:

]I need to decide wether I use RAID 0 (stripping) or RAID 5 for
]the tablespaces containing the data and the indexes.
]
]The database must run 24/24-7/7.
]
]In some books about Oracle, I read that using RAID 5 is not always a
]good choice for data (possible performance problems during write
]operations).

Simple striping will not give you the uptime you need. You need some redundant disk to achieve that. Realistically this means you are looking at simple mirrors, striped mirrors, or RAID5.

Both forms of mirroring will provide faster writes than RAID5.

RAID5 uses less disk (more disk space per dollar).

RAID5 is plenty fast enough for our operations here. The example is from a 10 Gig Oracle 7.1 database running Mincom's MIMS app with 140 concurrent users, about 50 of them "active" at one time according to the TP system.

Redo log file system, (striped mirror)

                        OPERATIONS           BLOCKS        AVG TIME(ms)
TYP NAME              READ     WRITE      READ     WRITE   READ  WRITE 
vol u09              21597    123347    830646   1236128   14.0    3.8 


rollback file system, (striped mirror)
                        OPERATIONS           BLOCKS        AVG TIME(ms)
TYP NAME              READ     WRITE      READ     WRITE   READ  WRITE 
vol u10              29926     93743    400794    785344   17.5    9.3 

Data file system (RAID 5)
                        OPERATIONS           BLOCKS        AVG TIME(ms)
TYP NAME              READ     WRITE      READ     WRITE   READ  WRITE 
vol u05             810136    307031  21472020   2912800   16.6   30.6 

My thoughts when setting this up was to buy enough disks to mirror redo and rollback, but RAID5 the archive re-do logs and the data/indexes. I left contingencies in the work order to buy more disks if the RAID5 write performace penalty was too much.

I turned out that the RAID5 is fine in our case. This is on a Sun 1000e host with a SSA110 attached and running Veritas Volume Manager.

Regards,
George.

-- 
   ,-,_|\   George Dau,
  /    * \  Unix (Solaris, DEC Unix, Linux), NT, Oracle, Internet.
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Received on Tue Aug 12 1997 - 00:00:00 CDT

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