IDS Forum

Re: Disk setup

Posted By: Art Kagel
Date: Wednesday, 30 October 2013, at 7:05 p.m.

In Response To: RE: Disk setup (LARRY SORENSEN)

I responded to Larry directly yesterday. There seems to have been a
problem with the IIUG Forums or the email gateway to them over the last 24
hours or so because I just saw about 15 posts from yesterday like this one
show up in my mailbox.

Anyway, the short answer to Larry was that RAID3 is OK and better than
RAID5 for write IO but no safer. Best to use RAID1 pairs for everything
for both performance and safety maximization carefully placing data on the
6 mirrored pairs to take advantage of all 12 spindles as much as possible.

Art

Art S. Kagel, Principal Consultant

Advanced DataTools (www.advancedatatools.com)
Blog: http://informix-myview.blogspot.com/

Disclaimer: Please keep in mind that my own opinions are my own opinions
and do not reflect on my employer, Advanced DataTools, the IIUG, nor any
other organization with which I am associated either explicitly,
implicitly, or by inference. Neither do those opinions reflect those of
other individuals affiliated with any entity with which I am affiliated nor
those of the entities themselves.

On Tue, Oct 29, 2013 at 2:47 PM, LARRY SORENSEN <lsorensen25@msn.com> wrote:

> I need to revisit this for our new server. We are setting up a cabinet
> with 12
> drives. The cabinet only supports RAID 0-5, so we can't do RAID 10 as
> hoped.
> What is the recommendation for the configuration, since you were so
> insistent
> on not using RAID 5? Thank you again.
>
> Larry
>
> > To: ids@iiug.org
> > From: art.kagel@gmail.com
> > Subject: Re: Disk setup [31753]
> > Date: Fri, 18 Oct 2013 09:50:10 -0400
> >
> > The default page size on all platforms except Windows, AIX, and MacOSx is
> > 2K (4K on those platforms). However, since version 10.00 any dbspace
> > except the rootdb dbspace and those holding logical or physical logs can
> be
> > any multiple of the default page size for the platform up to 16K.
> Informix
> > typically writes either a single page or up to 8 pages in a single IO, so
> > depending on the dbspace's page size, on Solaris, that would be from 2K
> to
> > 128K. If all of your dbspaces use 2K pages, then a block size of 32K
> works
> > very well and performance seems to start dropping off above 128K. Chunks
> > in dbspaces that use 16K pages, however, might do just as well with block
> > sizes from 256K to 1MB. But with a finite number of spindles, you may not
> > be able to build multiple RAID10 arrays with different block sizes for
> > different dbspaces. Like everything else we do as DBAs, this is a bunch
> of
> > tradeoffs.
> >
> > The thing to remember is that the RAID subsystem can only write a
> complete
> > stripe block to any drive, so even a 2K write must write out the entire
> > block (though not the entire stripe). Multiple contiguous writes from
> > Informix closely spaced in time can be coalesced by the system into a
> > single write, that's not guaranteed and unless you are in the midst of a
> > bulk load or during checkpoint chunk writes just doesn't happen very
> often.
> > LRU writes by the engine look mostly random to the RAID subsystem and
> > occur in fits and spurts so far less coalescing happens, so if the stripe
> > blocks are too big, you end up rewriting each block many times. We seek a
> > Zen-like balance. ;-)
> >
> > Art
> >
> > Art S. Kagel, Principal Consultant
> >
> > Advanced DataTools (www.advancedatatools.com)
> > Blog: http://informix-myview.blogspot.com/
> >
> > Disclaimer: Please keep in mind that my own opinions are my own opinions
> > and do not reflect on my employer, Advanced DataTools, the IIUG, nor any
> > other organization with which I am associated either explicitly,
> > implicitly, or by inference. Neither do those opinions reflect those of
> > other individuals affiliated with any entity with which I am affiliated
> nor
> > those of the entities themselves.
> >
> > On Fri, Oct 18, 2013 at 9:11 AM, Informix DBA <in4mixdba@gmail.com>
> wrote:
> >
> > > Do you know what block size informix uses on Solaris 11? Currently
> > > running 11.70.FC7W2.
> > >
> > > --David
> > > in4mixdba
> > >
> > > On Thu, Oct 17, 2013 at 11:45 PM, Art Kagel <art.kagel@gmail.com>
> wrote:
> > >
> > > > RAID10! Small stripe block sizes (32K to 1MB at most). SAN techs
> love to
> > > > configure arrays with huge block sizes from 256MB to 1GB which works
> well
> > > > for filesystems but is VERY VERY BAD for databases.
> > > >
> > > > Build multiple arrays of mirrored pairs so that you can isolate hot
> > > tables
> > > > and indexes from each other and from the logical and physical logs.
> > > > Ideally, if your logical log and physical log volume is below the
> > > > bandwidth available from a single drive then make a singleton RAID1
> > > > mirrored pair for the logs alone (or one for each logical and
> physical
> > > logs
> > > > if you need a bit more bandwidth) to keep the logs completely
> independent
> > > > of your mainline data and gather the remaining disks into a single
> big
> > > > RAID10 for your data and indexes.
> > > >
> > > > More spindles is better than fewer. If you can get more drives,
> double
> > > the
> > > > number and create the VG's for the database to use only the middle
> 30-50%
> > > > of the disk (ie not the outer or inner cylinders) and either leave
> the
> > > rest
> > > > of the drive's space unused or allocated to dbspaces for very low
> access
> > > > rate tables like historical or archival data tables.
> > > >
> > > > If space is tight, then build the biggest widest RAID10 array you
> can to
> > > > spread the IOs out.
> > > >
> > > > NO RAID5!!! NO RAID5!!! NO RAID5!!! NO RAID5!!! NO RAID5!!! NO
> > > > RAID5!!! NO RAID5!!! NO RAID5!!! NO RAID5!!! NO RAID5!!! NO
> > > > RAID5!!! NO RAID5!!! NO RAID5!!! NO RAID5!!! NO RAID5!!! NO
> > > > RAID5!!! NO RAID5!!! NO RAID5!!! NO RAID5!!! NO RAID5!!! NO
> > > > RAID5!!! NO RAID5!!! NO RAID5!!! NO RAID5!!! NO RAID5!!!
> > > >
> > > > RAID5 is not a safe place for your data! Period!
> > > >
> > > > See my presentation from the 2012 IIUG Conference entitled "Doing
> Storage
> > > > Right!" for details on why and the latest research on the subject.
> Also
> > > > look for my RAID5 Rant on the BAARF website (www.baarf.com) in the
> left
> > > > margin of the main page for a more complete explanation of why NO
> > > RAID5!!!
> > > >
> > > > Art
> > > >
> > > > Art S. Kagel, Principal Consultant
> > > >
> > > > Advanced DataTools (www.advancedatatools.com)
> > > > Blog: http://informix-myview.blogspot.com/
> > > >
> > > > Disclaimer: Please keep in mind that my own opinions are my own
> opinions
> > > > and do not reflect on my employer, Advanced DataTools, the IIUG, nor
> any
> > > > other organization with which I am associated either explicitly,
> > > > implicitly, or by inference. Neither do those opinions reflect those
> of
> > > > other individuals affiliated with any entity with which I am
> affiliated
> > > nor
> > > > those of the entities themselves.
> > > >
> > > > On Thu, Oct 17, 2013 at 10:51 PM, LARRY SORENSEN <
> lsorensen25@msn.com
> > > > >wrote:
> > > >
> > > > > Solaris 10
> > > > > IDS 11.5.FC7 - Growth
> > > > >
> > > > > I remember similar questions being asked in the past, but I can't
> > > > remember
> > > > > what the concenseous was. I am being given a cabinet with 12-146GB
> > > disks
> > > > > to be
> > > > > used as raw storage for a database. The SA is asking how I want it
> > > > > presented....RAID 0, RAID 5...etc. What is the best option.
> > > > >
> > > > > Thanks
> > > > >
> > > > >
> > > > >
> > > > >
> > > >
> > > >
> > >
> > >
> >
>
> *******************************************************************************
> > > > > Forum Note: Use "Reply" to post a response in the discussion forum.
> > > > >
> > > > >
> > > >
> > > > --001a11c233ea8d346304e8fbc410
> > > >
> > > >
> > > >
> > > >
> > >
> > >
> >
>
> *******************************************************************************
> > > > Forum Note: Use "Reply" to post a response in the discussion forum.
> > > >
> > > >
> > >
> > > --001a11c34f5c1cf7ca04e903aa8e
> > >
> > >
> > >
> > >
> >
>
> *******************************************************************************
> > > Forum Note: Use "Reply" to post a response in the discussion forum.
> > >
> > >
> >
> > --089e013d1866e05bb404e904358f
> >
> >
> >
>
> *******************************************************************************
> > Forum Note: Use "Reply" to post a response in the discussion forum.
> >
>
>
>
> *******************************************************************************
> Forum Note: Use "Reply" to post a response in the discussion forum.
>
>

--001a11c26e149af55604e9fd5d00

Messages In This Thread

• RE: Disk setup
  LARRY SORENSEN -- Thursday, 17 October 2013, at 10:51 p.m.
  • Re: Disk setup
    Art Kagel -- Thursday, 17 October 2013, at 11:45 p.m.
    • Re: Disk setup
      Informix DBA -- Friday, 18 October 2013, at 9:11 a.m.
      • Re: Disk setup
        Art Kagel -- Friday, 18 October 2013, at 9:50 a.m.
        • Re: Disk setup
          Informix DBA -- Friday, 18 October 2013, at 10:56 a.m.
          • RE: Disk setup
            LARRY SORENSEN -- Friday, 18 October 2013, at 1:57 p.m.
        • RE: Disk setup
          LARRY SORENSEN -- Tuesday, 29 October 2013, at 2:15 p.m.
        • RE: Disk setup
          LARRY SORENSEN -- Tuesday, 29 October 2013, at 2:47 p.m.
          • Re: Disk setup
            Art Kagel -- Wednesday, 30 October 2013, at 7:05 p.m.

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