January 24, 2006 at 11:32 am
Info: We are testing a server imaging product (Symantec's LiveState Advanced Server) that, in essence, let's us take a real-time image of a server (incremental images also supported). There is no need to reboot the server into a DOS-like mode (like GHOST). Furthermore, the LiveState images can be stamped down to dissimilar hardware than the original box (good for Disaster Recovery.)
According to Symantec, for a Sql Server incremental image, they "quickly" stop SQL server on the machine (to insure the integrity of the databases in the image), then restart sql server again!
My question is this: what happens if someone is accessing\updating the sql database at the moment they stop sql server? Do the standard MS MDAC components (ODBC, etc) automatically retry the operation when a failure is detected? Suppose the sql server is stopped and then an application tries to access/update the database. Does the ODBC driver, again, retry?
TIA,
Bill
P.S. I'm asking these questions because I don't think our applicaitons are coded to handle these types of retires.
January 24, 2006 at 2:19 pm
I believe it uses the volume shadow copy service and it doesn't actually stop the server it freezes it momentarily while taking a snapshot then unfreezes it. Since sp3 i belive volume shadow copy has worked fine and all symantec and all the other back up vendors are doing is taking advanatge of the vss service that micorsoft have provided. The applications should be totally unaware of what has happened.
We use this on our accounts server at work and our accounts applocations would not with stand any sort of glitch at all.
On an aside although live state does work we find that on certain servers the agent just dies (always the same servers the rest are fine) and the only way to fix it is to reboot the machine we have no idea why and symantec are typically unhelpful.
I personally would recommend that you try for at least a month before you buy it and if you find that some of the servers just stop backing up rest assured its not uncommon also once you get enough servers their admin app just locks up as you go from one server to another.
There are other vendors who provide similat capability and they pretty much all use vss service that's part of windows and so work in a similar mannner i would look at sonasafe or double take. If you get live state happy rebooting.
hth
David
January 24, 2006 at 7:32 pm
David,
Great response but I need a point clairifed.
>>we find that on certain servers the agent just dies.. >>
Are you referring to the sql server agent?
Also,
>>>if you find that some of the servers just stop backing up rest assured >>
Again, are you referring to Sql server's backup or LiveState?
TIA,
Bill
January 25, 2006 at 7:50 am
Live state agents and browser
January 31, 2006 at 8:50 am
I spoke with Symantec about LiveState 6.0. These said they use VSS to copy databases BUT for best results I should STOP/start the sql server engine before/after the image process. (That rules out daytime incremental images at our place). They claim they have seen cases, even with sql 2005, where sql ignored the requests of VSS to quiesce if sql was working on "a lot of data."
I don't know what to believe! Many backup programs have "open file" and sql "agents" that don't seem to make the same "hedge" (otherwise who would buy the product).
Any ideas on this matter much appreciated.
TIA,
Bill
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