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Data corruption - more possible in VM environment?

Posted on 2011-10-17
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the staff in this client place here say they had seen data corruption in physical machines only once in the last 12 years. but in the last 6 months, since VMs (wmware 3) were introduced, 3 times 3 different VM machine and a database in the instance got corrupted.. in all 3 times, some data was lost..

is this just coincidence or any real relation between the environment and the corruptions?
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Question by:25112
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Andrew Hancock (VMware vExpert / EE MVE^2) earned 1500 total points
ID: 36979634
Could you provide some more information about thje VMs, how the data was lost, error messages.

We've been involved and use virtualisation technologies for many years without incident, and we would say Disaster Recovery is far easier than physical!
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by:25112
ID: 36980278
the last time it happened, One day the apps just complained and we found that the date fields in the database had been corrupted and could not be reached.

again, this can happen in physical machines also, but it just so happens it is vmware3 in this case..

i am looking at all angles, but hence i am asking this question also..

an article came across that says some tech info:
http://www.sqlsolutions.com/articles/articles/SQL_Server_and_VMware-A_Potentially_Fatal_Combination.htm
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by:Andrew Hancock (VMware vExpert / EE MVE^2)
Andrew Hancock (VMware vExpert / EE MVE^2) earned 1500 total points
ID: 36980294
Well anything is possible, but without specific information, it's difficult to form a conclusion, I'm afraid.
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by:25112
ID: 36981409
hanccocka, below is the error from sql: does this help..

the link i gave you has an issue where vmware corrupts the data, but perhaps that is fixed with the latest version of vmware?
•	Table error: Page (1:879) allocated to object ID 314236343, index ID 0 was not seen.  Page may be invalid or have incorrect object ID information in its header.
•	Table error: Page (1:879) with object ID 314236343, index ID 2 in its header is allocated by another object.
•	Table error: Object ID 314236343, index ID 2. Page (1:879) is missing references from parent (unknown) and previous (page (1:878)) nodes. Possible bad root entry in sysindexes.
•	Table error: Object ID 314236343, index ID 2, page (1:879), row 486. Record check ((Record (i) == INDEX_RECORD || (Record (i) == GHOST_INDEX_RECORD && level == 0)) && Page->GetType == INDEX_PAGE) fail
•	Table error: Object ID 314236343, index ID 2, page (1:879), row 487. Record check ((Record (i) == INDEX_RECORD || (Record (i) == GHOST_INDEX_RECORD && level == 0)) && Page->GetType == INDEX_PAGE) fail
•	Table error: Object ID 314236343, index ID 2, page (1:879), row 488. Record check ((Record (i) == INDEX_RECORD || (Record (i) == GHOST_INDEX_RECORD && level == 0)) && Page->GetType == INDEX_PAGE) fail
•	Table error: Object ID 314236343, index ID 2. The next pointer of (1:879) refers to page (1:880). Neither (1:880) nor its parent were encountered. Possible bad chain linkage.
•	Row 32625 An error occurred while executing batch. Error message is: SqlDateTime overflow. Must be between 1/1/1753 12:00:00 AM and 12/31/9999 11:59:59 PM.

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by:Andrew Hancock (VMware vExpert / EE MVE^2)
Andrew Hancock (VMware vExpert / EE MVE^2) earned 1500 total points
ID: 36981644
No it does not help, you would need to supply a FULL break down of the environment, configuration, performance statistics, event logs on ESX, VMs and Storage.

How often does it happen, configuration of the SQL server, does the same thing occur, when the server is physical, SQL server updates, Patches on Windows server.

Or we could draw random conclusions, that it was caused because a  "penguin jumped off an iceberg"!

I do not have enough information, to formulate a diagnosis.
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by:andyalder
andyalder earned 500 total points
ID: 36986623
According to kb.vmware.com/kb/1008542 the article above is wrong, ESX doesn't cache writes.

The author is rather cagey about what hardware they have (You will not even find the configuration of the computer used for these experiments because it is rather unimportant.) but we know that they were using VMplayer under MS Vista. Vista is a workstation OS so by default turns the disk write cache on. If they used Windows server on the same hardware for the real machine test then by default that turns the disk write cache off.

It's quite likely that it is that that caused their data corruption (and the improved performance) when using VMware on Vista than when using a physical host; pity they don't say what OS was on the host for the non-VMware test.

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by:25112
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andy, thanks for the corrective post..
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