Re: postgresql cluster on SAN

How about i have one SAN storage for the slony master node and another
SAN to be share by slave nodes that only do SELECT?

Can Dell|EMC AX100i iscsi san with sata drive serve as storage for
postgresql server, will there be problem in I/O performance?

Chris Travers wrote:

> Spiegelberg, Greg wrote:
>
>> This is possible.  Below is a brief recipe.
>>
>> 1. Use Veritas Storage Foundation HA with Cluster File System.
>> 2. Have a volume with cfs available to 2 or more systems via SAN.
>> 3. Install PostgreSQL and be sure PGDATA is on the cfs mount
>> 4. Create a Storage Checkpoint of cfs mount (read-write virtual copy)
>> 5. Bring up PostgreSQL on node1
>> 6. Mount storage checkpoint on node2
>> 7. Start PostgreSQL on node2
>>
>> Drawbacks?  Heck yes.  There are many and you should understand the
>> nature of Veritas Storage Checkpoints before using.
>>
> Drawback #1-- only works read-only on all but one node.  And I am not
> even sure what will happen when you start writing on that one node...
>
>>  I have tested it
>> though in conjunction with dblink() and some other proprietary API's we
>> use for load balancing and the potential is there to manage many large
>> SELECT's.
>>
>>
> Ok, but what happens when you start doing inserts, updates, and deletes.
>
> Somehow I think that PostgreSQL's dependance on shmem and semaphores
> will cause corruption in your database as soon as you start writing to
> it on both nodes.  And I don't know enough about PostgreSQL's internal
> structure to know if writing on only one node is safe.
>
> Best Wishes,
> Chris Travers
> Metatron Technology Consulting
>
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