October 9, 2009 at 10:10 am
Krasavita (10/9/2009)
By looking at my results by DBCC page how do you see there is a problem????
Someone who knows the page structure really, really well (like Paul does) can look at the raw structure and see if things aren't as they should be. It really requires a massive knowledge of the page structure, so it's not something that most people could do.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
October 9, 2009 at 10:14 am
I need to explain at work, that this is not SQl, it is I/O, Paul can you please help me. Thank you
October 10, 2009 at 10:59 am
The explanation is: in all the cases where I've seen your error occur, and then disappeared again, it was the I/O subsystem. I've seen hundreds of such cases.
I can't give you anything better than that - you just have to trust me.
Paul Randal
CEO, SQLskills.com: Check out SQLskills online training!
Blog:www.SQLskills.com/blogs/paul Twitter: @PaulRandal
SQL MVP, Microsoft RD, Contributing Editor of TechNet Magazine
Author of DBCC CHECKDB/repair (and other Storage Engine) code of SQL Server 2005
October 12, 2009 at 5:42 am
Thank you fo ryour help, but By what errors you go by knowing there is a problem.
October 12, 2009 at 5:53 am
I'm not sure what you don't understand. You got I/O errors. They disappeared. The page with the I/O error was still allocated to the table in the error message. This means the I/O error was transient, which is your I/O subsystem going wrong. Possibly a stale read from a drive controller. I can't really explain it any more simply than that.
Thanks
Paul Randal
CEO, SQLskills.com: Check out SQLskills online training!
Blog:www.SQLskills.com/blogs/paul Twitter: @PaulRandal
SQL MVP, Microsoft RD, Contributing Editor of TechNet Magazine
Author of DBCC CHECKDB/repair (and other Storage Engine) code of SQL Server 2005
October 12, 2009 at 8:46 am
I don't understand what kind of I/O it is. Is it disk, cpu.. and What kind of subsystem diagnostics I need to check. Thank you
October 12, 2009 at 9:30 am
Krasavita (10/12/2009)
I don't understand what kind of I/O it is. Is it disk, cpu.. and What kind of subsystem diagnostics I need to check. Thank you
OK, let me try and explain.
I/O is disk.
so if you have I/O issues, it is down to the I/O System, whether is down to a local drive, SAN or network.
It is nothing to do with CPU...
The word that Paul used is 'transient' which means temporary. It was an ad-hoc error which indicates that there was a problem which happened and you cannot reproduce it. Paul knows this subject inside out, and his explanation is simple enough.
If you need to explain what has happened, it was a transient I/O error whcih caused this problem and you have had that confirmed/explained by someone who knows what they are talking about.
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October 12, 2009 at 9:48 am
Thank you,
Paul, one more question,you said
Our I/O subsystem isn't reading pages correctly. All the information I posted shows that page (1:38), which SQL Server complained was corrupt, isn't actually corrupt.
What do you mean by isn't actually corrupt. The way I understand and you can correct me:
after showing from DBCC my db was not corrupted, I/O is not working properly. My network admin, needs to know what kind of test to run. Thank you again
October 12, 2009 at 10:32 am
Krasavita (10/12/2009)
Our I/O subsystem isn't reading pages correctly. All the information I posted shows that page (1:38), which SQL Server complained was corrupt, isn't actually corrupt.What do you mean by isn't actually corrupt. The way I understand and you can correct me
The initial errors showed that a particular page was corrupt, i.e. damaged. That means that the page did not have the structure that it should have had. A later examination showed that the page was actually correct, ie undamaged, ie having the correct structure.
This means that your IO subsystem (that is, disks) is sometimes not returning the data it is supposed to. This is the same as if you opened a word document, and got an excel spreadsheet back. Sometimes the IO subsystem, when asked for a certain part of a file is returning a different part or is returning an old version.
Your network admin is not the right person. You need to speak to whoever is in charge of the IO subsystem. The server admin or the storage admin. This has nothing to do with networks. It has to do with disks, if you're using a SAN then it has to do with the SAN.
He needs to do tests on the entire IO system to ensure that it is performing correctly. If the storage admin/server admin knows his job, then he will know what kind of tests to run. If he does not, then he needs to contact the vendor that has provided the storage and get them to assist.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
October 12, 2009 at 3:53 pm
Krasavita - we're not trying to be obtuse when we're explaining things, but these really are very simple concepts that an administrator should understand. It may be that you're an 'involuntary DBA', in which case it makes sense that you're not following the explanations. You need to get someone to help you (actually there with you, not through the forums) who is familiar with this terminology, otherwise you're not going to be able to explain the issue to your management, as you've stated you need to do.
Thanks
Paul Randal
CEO, SQLskills.com: Check out SQLskills online training!
Blog:www.SQLskills.com/blogs/paul Twitter: @PaulRandal
SQL MVP, Microsoft RD, Contributing Editor of TechNet Magazine
Author of DBCC CHECKDB/repair (and other Storage Engine) code of SQL Server 2005
October 13, 2009 at 6:32 am
Thank you
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