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Home -> Community -> Mailing Lists -> Oracle-L -> Re: Recommendation for "cheap" HA solution
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Recommendation for "cheap" HA solutionHi!
When not having any cluster manager, there's 3 main issues what you have = to deal with:
If you do have lot's of storage space or do not have sharable storage, = then go with standby databases (can be done with standard ed. too) and = forget about issues in point 2.
So, you got to do some planning and scripting for that, but cheap HA for = simple systems is very possible. I personally like these simple = solutions over expensive software packages, guards, agents, which often = bring an additional layer of complexity to sysadmins jobs and don't = always work as expected themselves. But of course, these home-made = one-weekend solutions aren't appropriate everywhere...
Tanel.
Hi!=20
We are looking into establishing some sort of high availability = solution here. We are running 9.2.0 on Sun Fire 280 (2 processors).
Since we are on a tight budget, we are looking into various solutions = for HA.=20
One option would be to use Sun Cluster Server or Veritas Cluster = Server. If one box fails, the db just fails over to the other node. The = problem is that we don't have a cluster guy here...
The other Option would be to use RAC, but this is the most expensive = solution, I guess...=20
Does anybody use any other HA solution that is affordable? Failover = time should be less than 15 minutes, although "frequent" outages (i.e. = once a month or so) are tolerable.
Don't blame me for these requirements; it was not my idea...=20
This is 9.2.0 on Sun Solaris.=20
Thanks,=20
Helmut=20
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<DIV><FONT face=3DArial size=3D2>Hi!</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>When not having any cluster manager, =
there's 3 main=20
issues what you have to deal with:</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>1) hearbeat - verifying whether primary =
node (or=20
other nodes) are alive</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>2) storage - making failed node's =
storage=20
accessible to backup node</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>
<DIV><FONT face=3DArial size=3D2>3) connectivity - allowing clients to =
transparently=20
connect to another node (usually IP address transfer)</FONT></DIV>
<DIV> </DIV></FONT></DIV>
<DIV><FONT face=3DArial size=3D2>1) If you got max 15 min switchover =
time, it could=20
be done with a script on secondary or monitoring node, which actually =
verifies=20
whether your Oracle database is running (the easiest is=20
just connect and select * from dual in a script every minute). If =
either=20
connect or select fails, you take appropriate steps described =
below</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>2) storage - both of your servers have =
to see=20
the disks of course. If you got SAN over fibre, it's no problem to =
share=20
disks between several servers. With some external SCSI arrays it =
shouldn't be a=20
problem either to share between 2 servers. </FONT></DIV>
<DIV><FONT face=3DArial size=3D2>When your heartbeat mechanism detects =
that your=20
primary Oracle service isn't running, it first tries to kill Oracle and =
unmount=20
file systems on primary server - two nodes writing to the same data =
without=20
coordination will cause a mess. The kill & unmount could be done by=20
secondary or monitoring server using rsh, ssh or whatever remote exec =
mechanism.=20
If remote exec doesn't work, then we rely on ping, to see whether the =
primary=20
host is alive. When it isn't alive, we are free to mount file system on=20
secondary node and start the instance (of course the primary node should =
not=20
have automatic instance startup scripts in it's rc.d). The problematic =
issue is,=20
when ping show primary instance as alive, but remote exec to=20
shutdown&unmount fails. This is the place, where cluster managers =
should be=20
better than home-made high-availability solutions.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>3) For connectivity to be directed to =
backup node=20
you either try to transfer the IP in a script (I don't know solaris =
commands by=20
heart, you could just have two sets of network config files as well). =
Other=20
solution would be to play around with tnsnames.ora entries, which always =
have=20
primary host IP first in address list and secondary host as second. Also =
you got=20
to set fail_over or smth like that parameter in tnsnames.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>If you do have lot's of storage space =
or do not=20
have sharable storage, then go with standby databases (can be done with =
standard=20
ed. too) and forget about issues in point 2.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>So, you got to do some planning and =
scripting for=20
that, but cheap HA for simple systems is very possible. I =
personally=20
like these simple solutions over expensive software packages, guards, =
agents,=20
which often bring an additional layer of complexity to sysadmins jobs =
and don't=20
always work as expected themselves. But of course, these home-made =
one-weekend=20
solutions aren't appropriate everywhere...</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Tanel.</FONT></DIV>
<BLOCKQUOTE dir=3Dltr=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A title=3DHelmut.Daiminger_at_KirchGruppe.de=20
href=3D"mailto:Helmut.Daiminger_at_KirchGruppe.de">Daiminger, Helmut</A> =
</DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3DORACLE-L_at_fatcity.com=20
href=3D"mailto:ORACLE-L_at_fatcity.com">Multiple recipients of list =
ORACLE-L</A>=20
</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Thursday, July 24, 2003 =
5:49=20
PM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> Recommendation for =
"cheap" HA=20
solution</DIV>
<DIV><FONT face=3DArial size=3D2></FONT><FONT face=3DArial =
size=3D2></FONT><BR></DIV> <P><FONT size=3D2>Hi!</FONT> </P> <P><FONT size=3D2>We are looking into establishing some sort of high=20availability solution here. We are running 9.2.0 on Sun Fire 280 (2=20 processors).</FONT></P>
idea...</FONT> </P> Received on Thu Jul 24 2003 - 09:56:02 CDT
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