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Re: Is Raid 5 really that bad for Oracle?

From: Paul Drake <bdbafh_at_gmail.com>
Date: 3 Aug 2004 14:47:17 -0700
Message-ID: <910046b4.0408031347.69b0d183@posting.google.com>


Daniel Morgan <damorgan_at_x.washington.edu> wrote in message news:<1091542918.68711_at_yasure>...
> Connor McDonald wrote:
>
> > Niall Litchfield wrote:
> >
> >>"Cary Millsap" <cary.millsap .at. hotsos .dot. com> wrote in message news:<10gu902j8cmcs7b_at_corp.supernews.com>...
> >>
> >>>2. But mirroring is expensive per byte of storage. Hence RAID levels 2, 3,
> >>>4, 5, and 6 were proposed. Their design goals were to lessen the
> >>>expense-per-byte of storage of RAID level 1 (mirroring). For example, with
> >>>G=5 RAID level 5, the price of resilience per byte of storage is 5/4 of a
> >>>4-disk array instead of 8/4.
> >>
> >>I meant to make a similar point originally, but didn't. Namely that
> >>RAID5 tends to make sense from a COST/GB point of view and SAME tends
> >>to make sense from a COST/IO point of view. Often these two views are
> >>where the disagreement lies. If my sysadmins ask me how much storage I
> >>want, they do not want to be told (say) 100gb and 2500 IO/sec. They
> >>just want the former figure.
> >>
> >>Niall
> >
> >
> > True story...
> >
> > Company X moving from JBOD to SAN. JBOD totals around 800G so the SAN
> > is populated to 800G as well...Of course, in the JBOD, each 18G disk
> > ends up being around 17.5G available to the OS. In the SAN, each 36G
> > disk ends up being around 30G to the OS
> >
> > Result:
> > - They've halved the number of spindles
> > - They've not enough disk space
> > but hey...at least we've got a SAN
> >
> > :-)
>
> Good point. But is the database really writing to those spindles or is
> it, more likely, writing to a very large RAM cache rendering the loss
> irrelevant?

this just in:
http://www.intelfanboy.com/forum/showthread.php?p=1654#post1654

"The new Intel IOP332 Storage I/O Processor is aimed at cost-effectively enhancing RAID storage performance to help improve data reliability and reduce downtime. The IOP332 processor takes advantage of DDR2 400 memory and the fastest IntelŽ XScaleŽ core at 800 MHz to increase the speed of RAID5 data storage and recovery. The use of PCI Express technology eliminates the latency previously incurred by PCI-X bridges."

Inductively speaking ...
Improving the speed of RAID 5 must have been important.

or not.

-bdbafh Received on Tue Aug 03 2004 - 16:47:17 CDT

Original text of this message

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