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Re: Fwd: RE: RAID or NOT to RAID?

From: Joe Testa <teci_at_the-testas.net>
Date: Thu, 09 Aug 2001 11:55:24 -0700
Message-ID: <F001.003658F0.20010809084449@fatcity.com>

Paul, and that RH is not certified for 9i last i checked, :( although that doesnt stop some of us :)

joe
Paul Drake wrote:
>
> Hi all.
> I've been disconnected for awhile - found myself out in Nebraska.
> Installing 81715/Win2000 on a new Dell PowerEdge 2500.
> Only had 6 drives on 1 IO channel configured as 3 "containers" - RAID 1.
> The front grille reminds me of an electric shaver.
> It was the kinda trip that ended with me pulling a hamstring while
> unplugging a power cord for my notebook. Gotta stay hydrated and get
> that daily banana for potassium.
>
> repeat after me ...
>
> RAID 10 != RAID 0+1
> RAID 0+1 != RAID 10
>
> Even with only 4 drives, when they might seem the same,
> RAID 0+1 is stripe first, then mirror.
> RAID 10 is mirror first, then stripe.
> As someone once said, the best way to tell how its configured, is to
> pull a drive out of a hot swap bay, put it back in and see how many
> drives re-silver.
> A corollary would be - pull one drive - and then pull another
> non-adjacent drive (e.g. in the other cage). If its RAID 01 - you're
> completely hosed.
> So much for non-destructive testing. :)
>
> oh yeah, and "it depends".
>
> If you only need 8KB or 64 KB blocks at one time, go for neither, and
> just separate files onto different RAID 1 volumes of 2 disks each. If
> you're daring, don't even bother to use hardware RAID for the online
> redo logs - and just duplex them with multiple log members of a redo log
> group.
>
> After you locate what your point of contention is - either move the hot
> spots out to dedicated drives, or add more drives to the volume that has
> the most I/O.
>
> If you need massive amounts of data from full table scans - go for
> deeper stripes.
> Even numbers of drives in a volume are preferable for RAID 0 stripes,
> odd for RAID 3,5.
> This makes it easy to calculate the stripe depths as a multple of the
> db_block_size and OS io_size in your head.
>
> Gaja wrote a great section on this topic in the Performance Tuning 101
> Book.
>
> And you can "fix" the RAID configuration by simply deleting the existing
> RAID config - and starting from scratch. I had a site where a Dell Tech
> took a perfectly good 4 x RAID 1 (8 drives) config and turn it into a
> single RAID 0+1 config. <Ctrl-A> at boot gets you into where you can
> wipe it clean and start from scratch - assuming that you can wipe the
> slate clean.
>
> And I'll beat Joe T to the punch - since you're going to have to
> re-install the OS - Dell boxes run Linux pretty well.
> Just that Dell still sucks badly for calling RedHat Linux "Linux 7" on
> their store website.
> That still pisses me off.
>
> Linux != RedHat.
>
> Paul
>
> tday6_at_csc.com wrote:
> >
> > In a previous job I had to deal with this issue. WinNT 4.0 on a dual
> > processor Dell box with 24G of RAID. I had specified RAID 0 + 1 but
> > "someone" knew better and got it with RAID 5 (5 is obviously better than
> > 0). The SA wouldn't or couldn't reconfigure and the job needed to get
> > done.
> >
> > It was for a decision support system (basically read-only) and it may be
> > that sort of a system is less impacted. I abandoned any thought of OFA.
> > Just stick all the datafiles out on one directory branch (makes cold
> > backups easier) and let the RAID sort out the contention.
> >
> > I didn't like it because I was basically trusting to someone else's
> > decisions but performance was adequate and the task was successful. I'm
> > not sure that this would be true with an OLTP system.
> >
> > I've seen the notation RAID 10 (which is RAID 0 + 1). Perhaps we should
> > standardize on that. Obviously RAID 10 has to be twice as good as RAID 5.
> > Right?
> >
> >
> > "Denmark Weatherburne"
> > <denmark_weatherburne_at_ho To: Multiple recipients of
>list ORACLE-L
> > tmail.com> <ORACLE-L_at_fatcity.com>
> > Sent by: cc:
> > root_at_fatcity.com Subject: Fwd: RE: RAID or
>NOT to RAID?
> >
> >
> > 08/08/2001 02:47 PM
> > Please respond to
> > ORACLE-L
> >
> >
> >
> > Hi DBA's,
> >
> > I hope I'm not opening a can of worms, but I'd like your feedback on the
> > issue of using RAID 5 on NT 4.0 with Oracle 8.0.5.
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: Paul Drake
> INET: paled_at_home.com
>
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-- 
Joe Testa  
Performing Remote DBA Services, need some backup DBA support?
For Sale: Oracle-dba.com domain, its not going cheap but feel free to
ask :)
-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Joe Testa
  INET: teci_at_the-testas.net

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Received on Thu Aug 09 2001 - 13:55:24 CDT

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