Suspected Postgres Datacorruption

From: Sumeet Jauhar <sumeet(dot)jauhar(at)gmail(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Suspected Postgres Datacorruption
Date: 2011-08-03 07:35:29
Message-ID: CAKN1XtpsdHSJskgqFcNQGSFSLznKmE8D=SvM8wMr82GHmk6s0Q@mail.gmail.com
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Hi All ,

Can you please help me out with the following questions .

Our application is running on Postgres 7.4.X . I agree that this is a very
old version of Postgres and we should have upgraded . The issue that we
faced is that

1 . There was a system crash due to a hardware failure .

2 . When the system came up , we tried to insert a few records into the
database . However at this point in time we saw that Postgres was taking a
lot of CPU & memory .

Around 42% CPU consumption . This was a cause of concern .

3 . We re-indexed the database and it helped reduce the cpu & memory
consumption .

My question is

A ) Isn’t Postgres database resilient enough to handle hardware system
failure ? or it sometime results in a corrupt index for its tables ? I read
on the Postgres site that hardware failure can cause corrupt indexes .
Besides this are there any other scenario which may result in such
corruption .

B) If there has been improvement / enhancements done by Postgres regarding
the way it handles corrupt indexes can you please pass me more information
about the bug Id or some documentation on it ? Our application does not do
any REINDEXING . I am in a dilemma if we should seriously incorporate it in
our application .

I ideally want to push to a higher version of Postgres . If I can prove that
there will be significant performance benefits and that crashes won’t occur
then I will be able to present a strong case .

Since my question is related to Performance & Data corruption i saw on the
Postgres site that i should provide the following information

Addition Info :

CPU manufacturer and model : Intel's Itanium Processor

Do you use a RAID controller? yes

PCIe SAS SmartArray P410i RAID Controller

PCIe SAS SmartArray P411 RAID Controller

Is is Write back caching enabled ?

Total Cache Size (MB)............... 144
Read Cache........................ N/A

Write Cache....................... N/A

No of disks : 4

Have you *ever* set fsync=off in the postgresql config file?

#fsync = true # turns forced synchronization on or off

I never changed it .

Have you had any unexpected power loss lately? Replaced a failed RAID disk?
Had an operating system crash? Yes system crashed had occured .

Hope this information helps .

Regards,

Sumeet

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