Can torn page detection fire from existing corruption?

Does torn page detection only show new errors or errors during restore or
can it error due to a torn page that may have been in the database for a
while.
Thanks
Paul
AFAIK, torn page detection is done every tome a page is accessed from disk. This mean that it
doesn't matter when the page was torn.
Tibor Karaszi, SQL Server MVP
http://www.karaszi.com/sqlserver/default.asp
http://www.solidqualitylearning.com/
Blog: http://solidqualitylearning.com/blogs/tibor/
"Paul Cahill" <xyzpaul.xyzcahill@.dsl.pipex.com> wrote in message
news:O4XO3C8iFHA.3012@.TK2MSFTNGP12.phx.gbl...
> Does torn page detection only show new errors or errors during restore or can it error due to a
> torn page that may have been in the database for a while.
> Thanks
> Paul
>
|||Thanks Tibor.
Paul
"Tibor Karaszi" <tibor_please.no.email_karaszi@.hotmail.nomail.com> wrote in
message news:OMf$BV8iFHA.2644@.TK2MSFTNGP09.phx.gbl...
> AFAIK, torn page detection is done every tome a page is accessed from
> disk. This mean that it doesn't matter when the page was torn.
> --
> Tibor Karaszi, SQL Server MVP
> http://www.karaszi.com/sqlserver/default.asp
> http://www.solidqualitylearning.com/
> Blog: http://solidqualitylearning.com/blogs/tibor/
>
> "Paul Cahill" <xyzpaul.xyzcahill@.dsl.pipex.com> wrote in message
> news:O4XO3C8iFHA.3012@.TK2MSFTNGP12.phx.gbl...
>
|||I believe it is only when the page is written assuming you have torn page
detection turned on at the time of the write.
Andrew J. Kelly SQL MVP
"Tibor Karaszi" <tibor_please.no.email_karaszi@.hotmail.nomail.com> wrote in
message news:OMf$BV8iFHA.2644@.TK2MSFTNGP09.phx.gbl...
> AFAIK, torn page detection is done every tome a page is accessed from
> disk. This mean that it doesn't matter when the page was torn.
> --
> Tibor Karaszi, SQL Server MVP
> http://www.karaszi.com/sqlserver/default.asp
> http://www.solidqualitylearning.com/
> Blog: http://solidqualitylearning.com/blogs/tibor/
>
> "Paul Cahill" <xyzpaul.xyzcahill@.dsl.pipex.com> wrote in message
> news:O4XO3C8iFHA.3012@.TK2MSFTNGP12.phx.gbl...
>
|||Yes, the bits are flipped at write time (assuming db option is on). But detection (all 0 or all 1)
are at read time. At least that is how I read
http://www.microsoft.com/technet/pro...lIObasics.mspx (search for "torn")
and BOL
(mk:@.MSITStore:C:\Program%20Files\Microsoft%20SQL% 20Server\80\Tools\Books\createdb.chm::/cm_8_des_03_6ohf.htm).
I'm not 100% positive whether checking of inconsistent bits are always performed or only when db
option is set, though...
Tibor Karaszi, SQL Server MVP
http://www.karaszi.com/sqlserver/default.asp
http://www.solidqualitylearning.com/
Blog: http://solidqualitylearning.com/blogs/tibor/
"Andrew J. Kelly" <sqlmvpnooospam@.shadhawk.com> wrote in message
news:OTUksY9iFHA.1968@.TK2MSFTNGP14.phx.gbl...
>I believe it is only when the page is written assuming you have torn page detection turned on at
>the time of the write.
> --
> Andrew J. Kelly SQL MVP
>
> "Tibor Karaszi" <tibor_please.no.email_karaszi@.hotmail.nomail.com> wrote in message
> news:OMf$BV8iFHA.2644@.TK2MSFTNGP09.phx.gbl...
>
|||The check is only performed when the dboption is set, and only for pages
that have been written out since the option was set.
Paul Randal
Dev Lead, Microsoft SQL Server Storage Engine
This posting is provided "AS IS" with no warranties, and confers no rights.
"Tibor Karaszi" <tibor_please.no.email_karaszi@.hotmail.nomail.com> wrote in
message news:%23WoaD2DjFHA.1232@.TK2MSFTNGP15.phx.gbl...
> Yes, the bits are flipped at write time (assuming db option is on). But
> detection (all 0 or all 1) are at read time. At least that is how I read
> http://www.microsoft.com/technet/pro...lIObasics.mspx
> (search for "torn") and BOL
> (mk:@.MSITStore:C:\Program%20Files\Microsoft%20SQL% 20Server\80\Tools\Books\createdb.chm::/cm_8_des_03_6ohf.htm).
> I'm not 100% positive whether checking of inconsistent bits are always
> performed or only when db option is set, though...
> --
> Tibor Karaszi, SQL Server MVP
> http://www.karaszi.com/sqlserver/default.asp
> http://www.solidqualitylearning.com/
> Blog: http://solidqualitylearning.com/blogs/tibor/
>
> "Andrew J. Kelly" <sqlmvpnooospam@.shadhawk.com> wrote in message
> news:OTUksY9iFHA.1968@.TK2MSFTNGP14.phx.gbl...
>
|||Ahh, thanks. I assume there must be some flag in the page header saying something like "torn pages
flagged/flipped" (i.e. the page was written while detection was on) by which the code can determine
whether to check for tp or not?
Tibor Karaszi, SQL Server MVP
http://www.karaszi.com/sqlserver/default.asp
http://www.solidqualitylearning.com/
Blog: http://solidqualitylearning.com/blogs/tibor/
"Paul S Randal [MS]" <prandal@.online.microsoft.com> wrote in message
news:ujX3$2IjFHA.2180@.TK2MSFTNGP15.phx.gbl...
> The check is only performed when the dboption is set, and only for pages that have been written
> out since the option was set.
> --
> Paul Randal
> Dev Lead, Microsoft SQL Server Storage Engine
> This posting is provided "AS IS" with no warranties, and confers no rights.
> "Tibor Karaszi" <tibor_please.no.email_karaszi@.hotmail.nomail.com> wrote in message
> news:%23WoaD2DjFHA.1232@.TK2MSFTNGP15.phx.gbl...
>
|||So torn page detection wil activate only for fresh corruption.
That helps ie our problems are current.
We are in one of those situations where the db is corrupting but our disks
and controllers say all is well. We have turned off caching (batt backed)
etc.
No luck. We have installed sp4 and -T818. No errors from that.
We have run the new sqliostress. No lost writes, stale reads etc but still
the corruptions continue.
System, dell pe 8450 raid 10, had been stable for over 2 years.
We've built another box today and will move tonight.
Wish us luck!
Paul
"Tibor Karaszi" <tibor_please.no.email_karaszi@.hotmail.nomail.com> wrote in
message news:uK7U$GJjFHA.2852@.TK2MSFTNGP15.phx.gbl...
> Ahh, thanks. I assume there must be some flag in the page header saying
> something like "torn pages flagged/flipped" (i.e. the page was written
> while detection was on) by which the code can determine whether to check
> for tp or not?
> --
> Tibor Karaszi, SQL Server MVP
> http://www.karaszi.com/sqlserver/default.asp
> http://www.solidqualitylearning.com/
> Blog: http://solidqualitylearning.com/blogs/tibor/
>
> "Paul S Randal [MS]" <prandal@.online.microsoft.com> wrote in message
> news:ujX3$2IjFHA.2180@.TK2MSFTNGP15.phx.gbl...
>