We have mirrored db spaces on our production OLTP system - rootdbs,
physical log dbs and logical logs dbs. I can see the value for doing
this on rootdbs but am unsure of the other two so much. The reason our
system is as such is more out of years of habit from past DBA's,
sysadmins, etc. I am now reviewing whether this is the wisest course
and why we would or would not keep things like this - especially for
any future new hardware systems. Any feedback, input, comments or
suggestions is appreciated
Thanks!

If you do not mirror llog and plog then there is no point in mirroring
rootdbs
since if you loose one of them, the engine goes down.

Superboer


On 11 mei, 23:03, Tom Lehr <tomc... (AT) gmail (DOT) com> wrote:

What is the underlying disk structure? If the chunks are mirrored (say
RAID1 or RAID10) on disk then the Informix mirrors are redundant and are
costing you throughput. If on the other hand, your disks are not mirrored
(no RAID, RAID0, or <ick> RAID5) there is some benefit to mirroring them.

Art

Art S. Kagel
Advanced DataTools (www.advancedatatools.com)
IIUG Board of Directors (art (AT) iiug (DOT) org)

See you at the 2010 IIUG Informix Conference
April 25-28, 2010
Overland Park (Kansas City), KS
www.iiug.org/conf

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, May 11, 2010 at 5:03 PM, Tom Lehr <tomcaml (AT) gmail (DOT) com> wrote:

On May 12, 9:50*am, Art Kagel <art.ka... (AT) gmail (DOT) com> wrote:
"We" always said "always mirror your critical dbspaces somehow...",
whether it be Informix mirroring or hardware mirroring. As stated in
this thread, the engines "critical dbspaces are one such as the
rootdbs, any dbspace with logical or physical log files, etc YOU get
to determine which other dbspaces you consider critical.

I definitely prefer hardware mirroring now for multiple reasons.
Recovery of a dbspace mirrored within IDS ("informix mirroring") can
take quite some time depending on the size of the dbspace and the time
it's primary chunk(s) have been down. Hardware level mirroring is
typically much faster, although that of course depends on a number of
things. I defer to Art's comments on any RAID issues as he stated so
well.

Thanks -
Mark Scranton
www.markscranton.com