Hemant, Group,
Could not resist: here is my 0.02 Euro.
(0.05 by the time I re-read it)
Start with a Disclaimer:
Limited SAN experience:
HP-(ex cmpq) storageworks (EVA3000?) and
Dell/EMC/Clarion only.
Here is How I try to approach SAN:
Me, the DBA, wants;
- focus on mountpoints
- equal-everything
- no surprises (re-size?)
- no lock-in on disk, vendor or server.
Elaboration:
- Just Mountpoints,
I just want directories to place my stuff.
I don't want to be bothered too much with
the stuff below the mountpoints,
just make sure it is Raid10, striped, mirrored,
triple-powered, and no SPOF anywhere.
Make sure raid-groups are large enough so
throughput of N-disks is enough to keep up
with controllers, regardless of cache.
Sizes should be known, and fixed,
no surprises about hard/soft size-limits.
- equal everything.
- The least possible nr of components, and
- The least possible nr of Different components:
- Identical raid groups, if possible.
- 1 or two types of mountpoints only
- Preferably all of same "properties"
- Predictable (equal) performance on all
- e.g. all raid groups 4+4 disks of
140G each would result in mountpoints
of +/- 560G with equal properties.
- Few, Large mountpoints, if nothing else suffers
My perferred system would only grow
with (raid-groups/VG's of ) 8 disks at a time.
- I will re-insist on a equal playing field
for all disks again, because at some point,
I will have to compromise by putting a file
in a location where I did not plan it @1st.
- Snapshotting: per mountpoint or per directory,
which enbles me to copy/backup whole db at once.
Hence my reluctancy to dig deeper then mountpoints.
When LVM's distribute my mountpoints over >1 LUN
and snaphot happens at the LUN-level or deeper: BAD.
I often found I could not snapshot exactly the
subset of mountpoints(files) that I wanted.
- space for ORACLE_HOME preferably on a CFS,
so I only have to install once.
I tend to set oracle-home on the Shard-disks,
so I can mount or copy to multiple servers.
my internal server-disks are near-empty.
NB: like HP-UX style mirrored system disks,
you can take one out and get next server going
even faster then with ignite ;-).
(I would support OpenSSI.org, if I could,
I long back to the VMS style clustering).
Dislikes:
- Drivers not available for my unix/linux versions.
- LUN's or VG's unable to extend without rebuild
- LUN's or VG's with "different" characterisics.
- VG's filling up miraculously because of "soft" limits.
- snapshots not moutable on same machine (I'll give
the a different dir-name!)
- Snapshots-log full.
- Snapshot-logs on same raid-group as my redo-logs.
What I do not like (I'll repeat):
- mountpoints (or vol-groups, or Luns)
that are "faster" or "slower",
or behave differently from the others.
Any perceived "difference" will limit me
in my possibilities (or exposes me to
accusations: thou hast placed thy archives
on the slower disk!...)
If I have to separate :
- separate for safety : each vg should allow complete recovery:
vg1 : archs + 1-set-redo + 1 ctlfile
vg2 : datafiles + 1-set-redo + ctlfile
vg3 : depends...
- separate for perfomance : avoid hotspot in throughput:
vg1 : redos (on fastest disk, If there is one)
vg2 : data
vg3 : sort-space, archives, depends...
vg4 : depends... Keep monitoring !
btw: tuning the app or the data-model will gain more
then tuning the disks, quotes:
- The Brain is more intelligent then the Controller
- Less hardware is good for Innovation
- More Hardware should give you Less Status, not more :-)
Disclaimers ;
- 10G may upset all of this again.
- YMMV
Regards,
PdV
Oracle DBA - Certified
(you figure it out)
--
Please see the official ORACLE-L FAQ: http://www.orafaq.net
--
Author: Piet de Visser
INET: piet.de.visser_at_logicacmg.com
Fat City Network Services -- 858-538-5051 http://www.fatcity.com
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Received on Wed Oct 01 2003 - 02:44:29 CDT
