IDS Forum

Re: Are there issues when using RAW dbspaces o....

Posted By: Fernando Nunes
Date: Wednesday, 28 July 2010, at 4:18 a.m.

In Response To: Re: Are there issues when using RAW dbspaces on ID (Art Kagel)

I think nobody explains it better than Art, but I'd like to stress out two
points:

1- Every sysadmin talks about the advantages of journaling, but it's amazing
how these people forget about reality. Let's start with this Wikipedia
article:
http://en.wikipedia.org/wiki/Journaling_file_system
They split the journaling system into two: Physical and Logical. The first
logs all blocks (data blocks also) and the second only file metadata.
Let's dig into this: Physical has a lot of performance impact (which is
obvious) and it's ABSOLUTELY useless for databases, since the databases MUST
do this.
The logical journaling only stores metadata changes. PLEASE, can anybody ask
the sysadmin what kind of metadata is changes in a filesystem where only
Informix chunks are stored?! We don't (currently at least) change the size
of chunks...

2- The backup argument is alarming. And it does because this is not sysadmin
task or responsability, and the DBA must make sure this is his
responsability. Surely no one is thinking about doing filesystem backups of
database chunks with a live database...

Regards.

On Tue, Jul 27, 2010 at 10:59 PM, Art Kagel <art.kagel@gmail.com> wrote:

> YOW! Cooked spaces, Journaled filesystems (bet they want to use EXT4 to
> boot), AND VM images. You've got the triple crown there Jim! Lord God in
> Heaven, tell me they're not also saddling you with RAID5, RAID6, or RAIDZ
> on
> top of all that!
>
> 1) ESX doesn't care about RAW spaces AFAIK and VMs and RAW disk work about
> as well as VMs and any other form of storage, which is to say VERY BADLY!
> My testing for a major developer of highly embedded systems show that IO
> under a VM performs 10x SLOWER than IO performance on the underlying
> hardware/OS. I would seriously consider running your server on a commodity
> Linux box instead.
>
> 2) You are correct, of course. Any backup of Informix chunks made at the
> operating system level, especially if they are made, as seems to be the
> intent of your SAs, at the level of the underlying host OS, will be
> completely useless for restoring the database unless you put the engine
> into
> external back up mode and block transactions for the duration of the
> backup. Otherwise only an ontape or onbar backup will be usable to restore
> the engine.
>
> 3) That "little bit" is 10-20% performance increase of RAW device versus
> COOKED device, and an additional 5-10% for non-journaled filesystem chunks
> versus COOKED devices. That is without O_DIRECT enabled, but the cuts the
> cost down to about 5-10% RAW over COOKED and another 2-5% for filesystems,
> which while it is MUCH better, is not trivial. Add to that the extra cost
> of journaling (at least 5% but usually more like 15%) and the cost of doing
> all of this on a VM versus raw hardware (about 90% in my testing).
>
> 4) The journaling, as I've already stated is redundant and therefore a
> performance hit that buys you NOTHING! Informix's logical and physical
> logging is FAR more efficient at recovering the database after a crash and
> adding the filesystem recovery to that will only delay the beginning of the
> engine's fast recovery mechanism.
>
> 5) Run! Run fast and run far. You do NOT want to be associated with this
> system once it's rolled out.
>
> Art
>
> Art S. Kagel
> Advanced DataTools (www.advancedatatools.com)
> IIUG Board of Directors (art@iiug.org)
>
> 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, Jul 27, 2010 at 3:14 PM, Jim Cramer <jim-cramer@uiowa.edu> wrote:
>
> > HELP!
> >
> > Here is another angle to the recent questions, and explanations
> > by Art, et. al, regarding using RAW instead of COOKED dbspaces
> > on IDS 11.5 running on Linux.
> >
> > For reasons cited by Art and the others, I (the DBA) wish to use
> > RAW dbspaces when I move my instances to Linux (SUSE 11 SLES)
> > Virtual Machines on an ESX Server running VMWare.
> >
> > But my Sys Admins here are refusing to allow RAW spaces and citing
> > all kinds of vague, generalized reasons why, such as:
> >
> > 1) the "host administration utilities" will not fly right
> > with Raw Spaces but will not be specific about what would
> > go wrong. In general, my sense is that they feel that
> > the Management Console and Tools for the ESX host might
> > see the Raw Dbspace and, because it does not contain not a formatted
> > filesystem, allocate it to something on the box.
> >
> > 2) using raw space will not allow the VMs containing the IDS
> > dbspaces to be backed up or fit into their backup strategy
> > and backup utility.
> >
> > They cannot seem to understand that a normal backup utility
> > would not know how to deal with the dbspaces even if they
> > were Cooked.
> >
> > 3) that the "little bit" of performance that they claim I might
> > get with Raw will not pay back for the increased Sys Admin
> > overhead.
> >
> > 4) that they will use a Journaled File System (along with Cooked
> > dbspaces) because it is more robust, fault-tolerant, comes
> > back up quicker after a crash, etc.
> >
> > Can anybody provide me with any concrete information/experience
> > that is related to the above points, particularly (1) .
> >
> > Does anyone know if raw dbspaces can cause problems in a Virtual
> > Machine on a VMWare ESX Server.
> >
> > If you have some info and have time to send it soon, that would
> > be appreciated because I am about to do battle over this with
> > our Sys Admins.
> >
> > Thanks much in advance,
> >
> > Jim Cramer
> > Database Administrator and
> > Applications Developer III
> > University of Iowa
> > College of Engineering
> > Engineering Computer Systems Support
> > 1256 SC
> > Iowa City, Iowa 52245
> > (319)-335-5757
> > jim-cramer@uiowa.edu
> > jcramer@engineering.uiowa.edu
> > http://css.engineering.uiowa.edu
> > http://www.engineering.uiowa.edu
> > http://www.uiowa.edu
> >
> >
> >
> >
>
> *******************************************************************************
> > Forum Note: Use "Reply" to post a response in the discussion forum.
> >
> >
>
> --0016e659f7fea2c12b048c659cf6
>
>
>
> *******************************************************************************
> Forum Note: Use "Reply" to post a response in the discussion forum.
>
>

--
Fernando Nunes
Portugal

http://informix-technology.blogspot.com
My email works... but I don't check it frequently...

--0016364585e4393f9a048c6e4358

Messages In This Thread

• Are there issues when using RAW dbspaces on IDS 11
  Jim Cramer -- Tuesday, 27 July 2010, at 3:14 p.m.
  • RE: Are there issues when using RAW dbspaces on ID
    Wyza, Jonathon -- Tuesday, 27 July 2010, at 3:22 p.m.
    • RE: Are there issues when using RAW dbspaces o....
      jim-cramer@uiowa.edu -- Wednesday, 28 July 2010, at 11:15 a.m.
      • RE: Are there issues when using RAW dbspaces o....
        Wyza, Jonathon -- Wednesday, 28 July 2010, at 11:20 a.m.
        • RE: Are there issues when using RAW dbspaces o....
          jim-cramer@uiowa.edu -- Wednesday, 28 July 2010, at 11:48 a.m.
        • RE: Are there issues when using RAW dbspaces o....
          jim-cramer@uiowa.edu -- Thursday, 29 July 2010, at 9:55 a.m.
          • RE: Are there issues when using RAW dbspaces o....
            Wyza, Jonathon -- Thursday, 29 July 2010, at 10:34 a.m.
            • RE: Are there issues when using RAW dbspaces o....
              jim-cramer@uiowa.edu -- Thursday, 29 July 2010, at 10:56 a.m.
  • Re: Are there issues when using RAW dbspaces on ID
    Alexandre Marini -- Tuesday, 27 July 2010, at 3:30 p.m.
    • RE: Are there issues when using RAW dbspaces o....
      jim-cramer@uiowa.edu -- Wednesday, 28 July 2010, at 11:15 a.m.
  • Re: Are there issues when using RAW dbspaces on ID
    Art Kagel -- Tuesday, 27 July 2010, at 5:59 p.m.
    • Re: Are there issues when using RAW dbspaces o....
      Fernando Nunes -- Wednesday, 28 July 2010, at 4:18 a.m.
      • Re: Are there issues when using RAW dbspaces o....
        Art Kagel -- Wednesday, 28 July 2010, at 8:48 a.m.
        • RE: Are there issues when using RAW dbspaces o....
          jim-cramer@uiowa.edu -- Wednesday, 28 July 2010, at 11:40 a.m.
          • Re: Are there issues when using RAW dbspaces o....
            Art Kagel -- Wednesday, 28 July 2010, at 5:11 p.m.
      • RE: Are there issues when using RAW dbspaces o....
        jim-cramer@uiowa.edu -- Wednesday, 28 July 2010, at 11:31 a.m.
  • RE: Are there issues when using RAW dbspaces on ID
    Andrew Lennard -- Wednesday, 28 July 2010, at 12:19 p.m.

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