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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Raid 1 vs Raid 5 for tablespaces
Yes, it isn't quite the same as actually growing a RAID device, but it
kind
of looks like that in the end.
It certainly requires some good management skills, or you can create quite a mess.
With power comes complexity.
Jared
"Matthew Zito" <mzito_at_gridapp.com>
Sent by: ml-errors_at_fatcity.com
08/13/2003 05:14 PM
Please respond to ORACLE-L
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
cc:
Subject: RE: Raid 1 vs Raid 5 for tablespaces
Yes and no - its a semantical issue. If you want to grow a Veritas volume with the RAID under hardware control, either you need to have free space on the exposed RAID device the volume is using as a subdisk (to use Veritas parlance), in which case you're just using more free space on the existing RAID group, or you need to expand the volume onto another exposed RAID device. Either way, you're not actually "growing" the RAIDed device - just expanding the volume onto additional pre-existing space.
Certainly, all LVMs allow you to resize volumes - when they include a software RAID component, you gain an additional level of flexibility over what most hardware RAID arrays offer. Veritas, in my mind, is the gold standard. I haven't seen another LVM+RAID come close to the featureset and elegance that they offer.
Thanks,
Matt
-- Matthew Zito GridApp Systems Email: mzito_at_gridapp.com Cell: 646-220-3551 Phone: 212-358-8211 x 359 http://www.gridapp.com -----Original Message----- Sent: Wednesday, August 13, 2003 7:03 PM To: ORACLE-L_at_fatcity.com Cc: mzito_at_gridapp.com Importance: High You can grow volumes though without putting the RAID under software control. Veritas Volume Mgr allows you to do that. Jared "Matthew Zito" <mzito_at_gridapp.com> Sent by: ml-errors_at_fatcity.com 08/13/2003 09:14 AM Please respond to ORACLE-L To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> cc: Subject: RE: Raid 1 vs Raid 5 for tablespaces The _only_ even theoretical advantage to software RAID-0 is that software RAID implementations tend to have more flexibility than the hardware ones. For example, there are a number of software RAID implementations that allow you to grow RAID-0 volumes, something that is generally not allowed in hardware RAID, and most of those allow you to do it online. Some of the better software RAID implementations even allow for online volume type conversion - from RAID-1 to RAID-5 when adding a third disk to a mirrored pair, as a random example. Beyond that, there's no reason to have software RAID. Any other extraneous advantages can be gleaned by using a traditional VM on top of hardware RAID-ed devices. And even some of that stuff is better in hardware. :) Thanks, Matt -- Matthew Zito GridApp Systems Email: mzito_at_gridapp.com Cell: 646-220-3551 Phone: 212-358-8211 x 359 http://www.gridapp.comReceived on Wed Aug 13 2003 - 19:49:23 CDT
> -----Original Message-----
> From: ml-errors_at_fatcity.com [mailto:ml-errors_at_fatcity.com] On
> Behalf Of Jared Still
> Sent: Wednesday, August 13, 2003 11:54 AM
> To: Multiple recipients of list ORACLE-L
> Subject: Re: Raid 1 vs Raid 5 for tablespaces
>
>
>
> Tim,
>
> Are you suggesting that HW RAID 1 with SW RAID 0 is a better
> combination than HW RAID 1 and HW RAID 0?
>
> If so, why?
>
> Jared
>
> On Tue, 2003-08-12 at 21:59, Tim Gorman wrote:
> > Software RAID-1 can mirror across controllers, channels,
> and storage
> > arrays, should any of those be considered a
> single-point-of-failure...
> >
> > The combination of HW RAID-1 and SW RAID-0 is optimal for
> performance,
> > if the HW supports it...
> >
> >
> > on 8/12/03 9:04 PM, Matthew Zito at mzito_at_gridapp.com wrote:
> >
> > >
> > > Actually, as of AIX 4.3.3, it does support 0+1 for LVs, but that
> > > wasn't the scenario I was imagining. I was envisioning
> creating a
> > > set of RAID-1 raid groups on the storage array and then striping
> > > across them using the LVM. RAID-1 is one of those things
> that I feel
> > > is generally better to let your storage array handle - software
> > > RAID-1 requires your host to generate double the I/Os and
> should one
> > > side of the pair fail, hardware arrays tend to recover more
> > > gracefully than software raid. RAID-0, by comparison, is
> very easy.
> > >
> > > Thanks,
> > > Matt
> > >
> > >
> > > ----- Original Message -----
> > > To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> > > Sent: Tuesday, August 12, 2003 9:44 PM
> > >
> > >
> > >> The AIX LVM supports RAID-0 and RAID-1, but not together, as you
> > >> state.
> > >>
> > >> However, a rude form of RAID-0 can be achieved by specifying "max
> > > allocation
> > >> policy", which will cause round-robin distribution of physical
> > >> extents
> > > (PEs)
> > >> across a list of physical volumes (PVs), thereby approximately
> > >> RAID-0 at a large granularity (i.e. 4M, 8M, 16M per "stripe").
> > >> Still, it beats the
> > > heck
> > >> out of RAID5...
> > >>
> > >>
> > >> on 8/12/03 12:24 PM, Schauss, Peter at
> peter.schauss_at_ngc.com wrote:
> > >>
> > >>> Our hardware people tell me that our disk array will
> not support
> > >>> Raid
> > > 10.
> > >>> Given a choice between Raid 1 or 5 for my tablespaces,
> which one
> > >>> is best? This is Oracle 8.1.7 on AIX 4.3.3. The
> application will
> > >>> have a mix of read and write activity.
> > >>>
> > >>> Thanks,
> > >>> Peter Schauss
> > >>
> > >> --
> > >> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> > >> --
> > >> Author: Tim Gorman
> > >> INET: tim_at_sagelogix.com
> > >>
> > >> Fat City Network Services -- 858-538-5051
> http://www.fatcity.com
> > >> San Diego, California -- Mailing list and web
> hosting services
> > >>
> -------------------------------------------------------------------
> > >> --
> > >> To REMOVE yourself from this mailing list, send an E-Mail message
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> > >> also send the HELP command for other information (like
> subscribing).
> > >>
> >
> > --
> > Please see the official ORACLE-L FAQ: http://www.orafaq.net
> > --
> > Author: Tim Gorman
> > INET: tim_at_sagelogix.com
> >
> > Fat City Network Services -- 858-538-5051 http://www.fatcity.com
> > San Diego, California -- Mailing list and web
> hosting services
> >
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>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: Jared Still
> INET: jkstill_at_cybcon.com
>
> Fat City Network Services -- 858-538-5051 http://www.fatcity.com
> San Diego, California -- Mailing list and web hosting services
> ---------------------------------------------------------------------
> To REMOVE yourself from this mailing list, send an E-Mail message
> to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru')
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-- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Matthew Zito INET: mzito_at_gridapp.com Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: INET: Jared.Still_at_radisys.com Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
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