IDS Forum

RE: Implementation of Informix on 3 hdd

Posted By: Paul Watson
Date: Monday, 29 October 2012, at 12:15 p.m.

In Response To: Re: Implementation of Informix on 3 hdd (Art Kagel)

Does the HW raid not suppor extended RAID10 - if it does then you could
raid all three drives

Cheers
Paul

-----Original Message-----
From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of Art
Kagel
Sent: Monday, October 29, 2012 11:12 AM
To: ids@iiug.org
Subject: Re: Implementation of Informix on 3 hdd [28664]

Marc:

I would agree with Andrew on most points:

- Try to get a fourth drive to mirror your #3 drive for safety.

- If your data is not on a mirrored drive it is not safe, even if the

logs are on mirrored drives.

- If you do mirror #3, then your plan should be:

1. Place OS, database logical and physical logs on the mirror formed

from drives #1 & #2

2. Place data on the mirror formed from drives #3 & #4

- If you do not mirror #3, then follow Andrew's plan:

1. Place important OS filesystems (like root and boot) on the

mirrored pair (#1 & #2) along with all database chunks except
temp dbspaces

2. Place temp dbspaces and non-critical filesystems on drive #3

To answer your question about mirroring, the mirror writes in a RAID1 or
RAID10 configuration are simultaneous but not synchronous. In the old days
mirrored drives were spindle locked. They connected to each other so that
their spindles spun at the identical speed with the same sector on each
drive under the read-write heads at the same time by sharing a timing pulse
so that writes were purely synchronous. That is no longer done for many
reasons. One of the most important of those is that without the
synchronization, the firmware or software can read different sectors from
each drive in the mirror in parallel effectively doubling the read
throughput from the pair for short periods of time. This means that even
though the two writes are issued to the controller simultaneously, the
physical writes to the two drives many not happen at the same instant
because of the different head positions and platter rotational positions.

Art

Art S. Kagel
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 Mon, Oct 29, 2012 at 11:27 AM, MARC SAETTEL
<m.saettel@greenivory.com>wrote:

> Hi guys,
>
> I'm looking for your view about a physical implementation of Informix.
>
> I want to implement Informix 11.50 on 3 hdd for a better performances ,
> but my
> aim is also to have a crashproof system with solid performances.
> The goal is to maintain the instance working even if a hdd crash
> (physically)
> without any looses.
>
> hdd1 (OS) : System RAID
> hdd2 (OS) : System RAID logical logs + mirroring
> hdd3 (datas) : dbs_data
>
> For doing this i will mount 2 hdd for OS in RAID, so if one of both crash
> we
> can directly change it on the fly.
> If the dbs_data hdd crash then the mirror can be use even if the
> performance
> will be poor because everything is on the same hdd.
>
> Is this a clean infrastructure ?
>
> The bonus question is the documentation the mirroring is describe a one
> request and 2 simultaneous write on both disks but is this a full
> synchronous
> mecanism.
>
>
>
>
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Messages In This Thread

• Implementation of Informix on 3 hdd
  MARC SAETTEL -- Monday, 29 October 2012, at 11:27 a.m.
  • Re: Implementation of Informix on 3 hdd
    ANDREW FORD -- Monday, 29 October 2012, at 11:48 a.m.
  • Re: Implementation of Informix on 3 hdd
    Art Kagel -- Monday, 29 October 2012, at 12:12 p.m.
    • RE: Implementation of Informix on 3 hdd
      Paul Watson -- Monday, 29 October 2012, at 12:15 p.m.
    • Re: Implementation of Informix on 3 hdd
      MARC SAETTEL -- Tuesday, 30 October 2012, at 4:20 a.m.
      • Re: Implementation of Informix on 3 hdd
        ANDREW FORD -- Tuesday, 30 October 2012, at 9:40 a.m.
      • Re: Implementation of Informix on 3 hdd
        Art Kagel -- Tuesday, 30 October 2012, at 3:54 p.m.

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