Although I agree with these recommendations, I don't agree that "Oracle
is such an I/O hog". Oracle was designed to perform I/O efficiently
and generally does so. Poorly-written SQL can create an I/O
bottleneck, but it's not the fault of the RDBMS.
- lembark_at_wrkhors.com wrote:
> You are almost always better off with more spindles to
> spread the load over. With fewer disks you get the same
> total storage but less flexability in how the I/O is
> partitioned between devices. Since Oracle is such an I/O
> hog the added flexability can be a real lifesaver.
>
> Hitachi's claim that there isn't any benefit to spreading
> out the I/O may be valid with huge amounts of cache. The
> technology for disk I/O manglement is always improving,
> so is the quantity of... er... "hooey" available from
> sales reps; the answer to your question is probably "both" :-)
>
> Personally I'd go with more disks using RAID5 w/ a stripe
> size equal to the O/S page (e.g., 4x1K or 8x1b for a 4KB
> file i/o page or 8x1k for an 8K system page). This avoids
> extra overhead from the RAID5 parity writes (you have to
> hit all the disks every time anyway) and gives you back
> a lot of extra storage over mirroring. Using the RAID5
> w/ a reasonable stripe also allows you to spread the I/O
> over multiple RAID's to balance the load -- sine the RAID
> set is the "PV" managed by your LVM system. The extra disks
> come in handy at this point because you can create more
> RAID sets for balancing the load.
>
> In theory if you have enough cache none of the disk parameters
> matter at all. Then it depends largely on your budget for
> cache and how well the current Hitachi controllers manage it.
> If you don't have infinte faith in their cache management
> system then more disks is the better bet.
>
>
>
> --
> Steven Lembark 2930 W. Palmer
> Workhorse Computing Chicago, IL 60647
> +1 800 762 1582
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Received on Tue Dec 18 2001 - 18:05:51 CST
