Hello All:
I have a requirement to design High Availability for
an Application that is using a robust MySQL DataStore.
I am thinking of the following configuration. My
previous configuration for HA got exposed for being a
leaky boat on this list (Subject: Advise on High
Availability configuration).
CONFIGURATION:
- Two machines, Primary and Secondary. Each machine
has the __capability__ to run an instance of our
Application and an instance of MySQL Server.
- A Heartbeat Manager runs on both boxes providing
the status of the machines, UP or DOWN.
- Additionally, I will setup a SCSII controller in
the Primary and Secondary Application machines so that
the actual data store (disk drive) runs on another
physical machine in a disk-array (RAID).
- With this setup the MySQL Servers on both the
machines will write/read data to/from this disk array.
INITIAL STATE:
- The Heartbeat Managers are running on both the
machines.
- The Application and the MySQL process on the
Primary are Active, performing database operations at
any given time.
- The Application and the MySQL process on the
Secondary are __not started__.
OPERATION:
- The Primary machine goes down. The Heartbeat Mgr
on the Secondary becomes aware of this and performs
the following operations on the Secondary.
* Stop (Kill) the Application running on the
Primary.
* Stop (Kill) the MySQL process on the Primary.
* Run tools programmatically to ensure the data
integrity of the DataStore.
* Start the MySQL process on the Secondary.
* Start the Application on the Secondary.
- The Secondary is now ACTIVE and will start
servicing requests.
- I am guaranteeing that only one MySQL Server will
be accessing the DataStore at any given time.
CAVEATS:
I have been made aware of the following caveat in the
above configuration.
- The DataStore is the single point of failure.
Does the step of trying to run table repair and
data recovery operations on the DataStore when the
Secondary takes over alleviate this issue?
QUESTIONS:
- Have any of you seen such a configuration being
deployed?
- Do you see any big gotcha's in this configuration?
- Will Stopping (Killing) the Primary MySQL Server
release all the locks it was holding on the DataStore?
- Is it possible to run the Table Repair and data
recovery tools programmatically (non-manually)?
I look forward to your feedback and comments. Thank
you.
Gowtham.
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