UKOUG RAC & HA SIG 11 February 2009

Cold journey downwards to Slough, and somehow I managed to completely tear to shreds the back of my shirt  just by stretching too much, a bit like the Incredible Hulk. Oh dear, at least I did not turn green.

Astonishingly quiet attendance at the first RAC sig of the year. Not sure whether it is a sign of economic doom and gloom, or a reflection on the agenda, which seemed a bit light, and far too much vendor led.

Julian Dyke outgoing chairman gave a valedictory speech as he has to stand down as chairman of the RAC SIG, now that he has been elected to the UKOUG board.

The days agenda has a theme around replication – not a bad idea having a theme, as I say just a shame it was so vendor led.

Survey of who is using what still going:

#nodes in cluster:  vast majority of 2 a sprinkling of 3 and 4.

vast majority running on Linux almost 50/50 32bit and 64bit, majority on RHEL. none on oracle enterprise linux.

sprinkling on windows, a little bit more on Solaris Sparc, and a couple on HP-UX.

A few on 9.2, a couple on 10.1, vast majoirty on 10gR2, no one has got 11.1 RAC in production.

No one using RAC with iSCSI, a couple on NAS, and most on FC.

EMC largest storage vendor, a few HP’s, IBMs, Netapp.

A good number using ASM, a few with OCFS1/2

I think these survey numbers have been fairly constant for a while now.

Oracle Support Update – Phil Davies.

Usual support update from Phil.

Of note is that will be the terminal release, for 10gR2.

Looks like an interesting bug in Rolling upgrade to ASM fails MetaLink Note: 742647.1 There is a patch for this issue.

Streams Based Replication – Martin Bach

Martin is one of the most knowledgeable guys around, and in December he obtained the Oracle Certified Master qualification.

This was a nice presentation giving a grounding in how Oracle Streams works.

Streams primer:

  • Captiure
  • Propagation
  • Apply

Streams is versitile but complex, the Oracle documentation runs to 3 manuals just for streams. As streams is not really a well used database feature there can be a lot of bugs with it. Note 413353.1

There was also a good discussion of some issues Martin has encountered while running streams.

Minimising downtime when upgrading/migrating Oracle with Goldengate – Ian Richardson

Goldengate does replication including bi-directional replication

The architecture of goldengate seems quite similar to oracle streams, has a capture, paropagate, and deliver (or apply) process. It’s completely platform independent can use it to go from 1 type of platform to another, or indeed 1 oracle version to another. It does seem like a great way of minimising downtime during migrations/upgrades.

Lessons From a 2 year stretch with an extended RAC Cluster – Pavel Rabel

Extended RAC is having RAC nodes separated by quite a distance. This is lessons from BT.

In 11g docs Extended RAC is becoming an accepted architecture. ASM with normal redundancy can be used to spread the data across multiple disk arrays in the separate datacenters.

30KM between the two datacenters, I think he said 0.2ms ping round trip time.

Used ASM to migrate from original storage to new storage

Could not add/remove css votedisk while nodes were up, cluster downtime was required. Fixed 11g

ouch! They run dd on the incorrect disk

Created 3rd failgroup which meant some extents got mirrored within a datacenter

ASMLib using emcpower device, but after restart single path devices used after restart.

Found accessing local devices were 10-20% times faster than accessing the remote disks.

11g ASM benefits for extended RAC

ASM_PREFFERED_READ_FAILURE_GROUPS allows you to specify only local access to diskgroups – allowing secondary extents to be read as well, rather than just always primary extents

FAST Mirror Resync changes are tracked

Contiuent Replication & Oracle – Eter Pani

I did not like this talk. I’m afraid it semed a little shambolic.

Oh my god, he has just said it’s “almost working” does replication master-slave, and master-master might work someday. originally built with mysql. Might work with oracle.

Continuent is cheap, that seems to be the main selling point.

Continuent seems to work by extracting sql from the redo logs and firing these sql statements at the target database. No parallel applier.

I don’t think you would want to use this product for serious Oracle deployments.

Next meeting RAC & HA SIG meeting is 16th June in London, see you there!


8 thoughts on “UKOUG RAC & HA SIG 11 February 2009

  1. Hi Jason, thanks for sharing this!
    I wonder how golden gate compares to streams in ‘real life’, that is on stability issues (aka bugs) as well as performance.

  2. Hi Luca,

    Thanks for reading!

    That is a good question, I do know that Oracle employees have used goldengate on projects here in the UK, so knowing how many problems streams can have, that might give you an idea!

    Of course goldengate is a high cost option, on top of Oracle whereas streams is not.


  3. Hi Jason

    Thanks for the summary and comments on the RAC & HA SIG event. I take your point about the agenda being a little thin (I hold my hands up about this – I was under time pressure for getting the agenda together)- the day really needed one more session. I’m also not convinced of the value of theme based meetings; they seem to tend to put people off from attending if the theme is not relevant to them. Rest assured that the June session will have much more (in depth) content and will be more broadly based. Many thanks again, for your feedback on the session.

    Kind regards,

  4. Hi Dave,

    Thanks for dropping by and commenting, and congratulations on your election!

    Look forwards to the june event, see you there.

  5. Jason – thanks for the write-up. I couldn’t make it to this event but regarding the Continuent session I saw a similar session (by one of the US-based Continuent guys) at UKOUG 2008 in Birmingham. That presentation was quite good (no demo though) and explained what they were doing pretty well. I do find it quite cheeky for them to call it “Open Source replication” at Oracle-only events though when you have to buy their Oracle redo log extraction component! However, as you say, cost is their main differentiator (afterall, I don’t think Oracle to MySQL is a requirement for most people), mainly as you can replicate between, say, Standard Edition databases.

  6. Hi Simon,

    Yeah, I think quite a few people found “Open Source replication” pushing it a bit far.

    Unfortunately the guy presenting was not helping make the case for it.


  7. Hi Dave,
    I agree that “almost working” is not the best recommendation for the product.
    But it is realistic. I have said these words deliberately.
    It was not marketing presentation and I am not the sales person to show unreliable product as good one.


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