Many thanks to the few who answered to my original posting :
Jean Dubois j_dubois_at_mtl.digital.ca
Helgi Viggosson helgi_at_ott.is
Lee Askew Lee.Askew_at_jcu.edu.au
o My original posting was :
+++++++++++++++++++++++++
>I would like to get comments and experiences on installing an Oracle database
>over ADVFS, instead of staying with the 'we know it works fine' rule of thumb
>which recommend raw devices.
>Does anybody have values and remarks on the performance degradation inherent
>to using the O/S File System?
>For those who decided to install Oracle databases on top of Advfs, do you make
>use of the nice features of Advfs :
>- do you clone the File System whilst Oracle is running (hot backup purpose) ?
>- do you HOT migrate and defragment ?
>- did you stripe the datafiles over n axis thanks to ADVFS, or did you only
>consider the general advises provided by Oracle (different tablespaces split
>over existing axis)
>Of course, I will summarize your answers
>Jean-Claude.Petiot_at_iea.fr
>International Energy Agency - Paris
o My attempt to summarize :
+++++++++++++++++++++++++
Even if I didn't got the precise information I was expecting (thought somebody
from Oracle familiar with Advanced tools over Digital Unix would answer), I
get the feeling that ADVFS brings enough resizing and on line administration
facilities to be considered as a must. On the performance side, my understanding
is that using the file striping can provide a comparable performance level than
using basic raw devices, but no formal statement has been established.
Some of you do recommend to stripe datafiles, other to manually distribute the
datafiles among the existing disks. Seems also that Advfs performances are
improved with 3.2.
Helgi uses on-line defragmentation, and reduces database shutdown to a very
short period once a week thanks to a clone file set.
Lee strongly argues for a RAID 5 configuration, I consider we have a
configuration at least as good on the paper in terms of performance and
availability (probably much more expensive !), with LSM + ADvfs Utilities.
This allows to setup a Raid 0+1 configuration (mirroring disks with LSM, and
stripping the files with ADVFS)
Jean-Claude
o Answers :
+++++++++
Jean Dubois :
-----------
Salut Jean-Claude,
While I was still a DEC, I ran an Oracle benchmark using datafiles on
ADVFS. The purpose was to stripe the datafiles. This was not done
without trouble, but the results were impressive. I don't remember all
the details, but here are the general lines:
1) You create AdvFS partitions for your datafiles
2) Install Oracle the standard way, and create the database
3) Once this is done, shutdown Oracle and do the following:
a) Create another data file right beside the original one
b) Turn on stripping on this new file (stripe(8) )
c) copy the contents of the original datafile to the striped one
d) Using Oracle DBA change the location of your datafile to point to
the new one
Et voila! You have your self X time the IO performance for this datafile
(X being your volume count).
Hope this helps
Helgi Viggosson :
---------------
I use AdvFS on top of LSM for all my file systems, including for Oracle
database files. So far my experience is all on the positive side.
Performance wise, I've compared it with UFS, only to find out it is very
similar, although I did notice an improvement in AdvFS performance after
upgrading from 3.0 to 3.2.
I've uitlized most of the advanced features of the file system, including
on-line (HOT) migration, defragmentation (scheduled once a week during night)
and striping. To take a cold backup of the database, I use the following
sequence:
1) dbshut
2) create and mount the clone
3) dbstart
4) vdump the file set
This means the database goes offline for only fraction of the time it would
otherwise, but still guarantees database integrity.
Currently I use archive mode for hot-bacups of Oracle databases, but I plan to
purchase the Oracle Application Specific Module for Polycenter NSR (Networker)
when it becomes available from Digital.
I've tried striping vs distributing the files among the disks, and my intermediate
conclusion is that the latter gives better performance. But I've to note that
my testing wasn't very thorough, with only 5-user simulated load over 3-disks.
By having multi-volume AdvFS domain (and manually migrate the files among the
volumes for optimum performance) vs multiple domains each with one disk gives
I think very comparable result. Point of note, I mirror all my volumes with
LSM.
Regards,
Helgi.
Lee Askew :
-----------
Jean-Claud,
We are running Oracle 7.2.2 on an Alpha 2100 dual processor, with ADVFS
under RAID 5.
And I Like it...
ADVFS IMHO is excellent, the ability to resize partitions on the fly, for
me is worth it by itself.
The RAID whilsh IO is DEFINITELY slower for some applications BUT faster
for others is definitely worth it as well. We Have already had a disk
fail in a raid set and processing continued albeit a little slower.
Anyways back to the ADVFS, we found it simple to setup, format partitions
etc etc. As for performance ADVFS against the normal unix format, IMHO I
cannot see much difference at all, infact negligable(sp?).
> Does anybody have values and remarks on the performance degradation
> inherent to using the O/S File System?
> For those who decided to install Oracle databases on top of Advfs, do
> you make use of the nice features of Advfs :
> - do you clone the File System whilst Oracle is running (hot backup
> purpose) ?
I havent done this yet.
> - do you HOT migrate and defragment ?
we have defragmented online without problems.
> - did you stripe the datafiles over n axis thanks to ADVFS, or did you
> only consider the general advises provided by Oracle (different
> tablespaces split over existing axis)
As previously mentioned we use RAID 5 for redundancy and I would
recommend RAID 5 to anyone.
There is no doubt that IO is definitely quicker by either using raw
partitions or just ADVFS without RAID; infact from what I can gather and
with speaking to other systems guys they have indicated about a 15-20% io
performance drop. And it would appear that this is true depending on the
application.
RAID 5 is very suited for large non-volatile files.
ie. RAID likes VERY large files.
RAID's performance appears to degrade when you have thousands of very hot
files being accessed, since you will end up with disk contention; in this
case i would recommend a mirrored set.
What we did was mirror our system disk, which also includes oracle
sources etc. And placed our database - datafiles/rollbacks/temporary
tables etc etc on the raid set. There was no need to split the database
into seperate tablespaces since RAID is splitting the file over multiple
spindles anyway (another bonus IMHO).
Anyways not much else to say, BUT I would definitely recommend ADFVS and
RAID 5 if you require it. We havent had a problem with either the ADVFS
or the RAID/Mirror sets..
Please let me know if I can help you in any way. I hope that I have
answered some of your questions.
Thanks Lee.
Received on Tue Nov 07 1995 - 13:09:26 NZDT