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Thread: RAID Technologies and ORACLE 8i

  1. #1
    Join Date
    Oct 2000
    Hi.. I do not have a complete understanding of these RAID technologies, but now I need them. We are presently using RAID5 with a pool of disks. I was reading through some stuff to become aware that people are discussing a lot about RAID5 vs 0+1. Which is good and better and so on??
    Can we use both at the same time.. Meaning that can we use RAID1 Mirroring (couple of disks) for logfiles, controlfiles and temporary tablespace. The maximum space I can use from this disk is about 3 GB I suppose and these disks are 50GB each.. So, the rest (Datafiles) as RAID5.. Is there any disadvantage if I propose this. How hard it is or how practical it is for Sysadmins to maintain 2 or 3 different RAID systems on one bay or so..

    What is the disadvantage of having Redologs, CTL files, Temp TS on a RAID5 system. I know they are accessed sequentially and datafiles are accessed randomly, but I am unable to understand the true impact that people fear about.

    What is Software based RAID and Hardware based RAID?

    What is a Controller and what does it do?

    Thanks, ST

  2. #2
    Join Date
    Nov 2000
    A good place to start learning about RAID is at

    A RAID 0+1 (Striping + Mirroring) filesystem is by far the fastest filesystem for Oracle Databases. However, the cost is usually prohibitive except for the most critical databases.

    A RAID 5 (Parity Striping) filesystem is good for Oracle databases, but suffers during writes. This is a good compromise for read-heavy and write-lite applications.

    It is perfectly reasonable to mix and match RAID types in one system. In fact, I believe it is the best way to maximize your investment in the hardware.

    Software RAID is where a program running on the host controls the RAID. This is typically the slowest RAID system. A hardware RAID system has a dedicated controller (hardware device) that calculates parity and controls the Disks. Hardware RAID devices usually have Cache associated with them whereas Software RAID usually does not.

    Having Redo Logs, Controlfiles, TEMP on a RAID 5 device, IMHO anyway, is better than having them on a single disk with no redundancy. Having them on a 0+1 filesystem is even better.
    Jeff Hunter
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