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DBADave
Constraint Violating Yak Guru
366 Posts |
 Posted - 2005-10-26 : 15:23:07
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| I've read several oppinions on controller cache settings and the answers appear split. Some people say to configure 100% Write / 0% Read, while others indicate 100% Read and 0% Write. If 100% Write is the desired setting, what is the risk of losing data due to a power outage.Dave |
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SQLServerDBA_Dan
Aged Yak Warrior
752 Posts |
Posted - 2005-10-26 : 15:55:12
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quote:
Originally posted by DBADave
I've read several oppinions on controller cache settings and the answers appear split. Some people say to configure 100% Write / 0% Read, while others indicate 100% Read and 0% Write. If 100% Write is the desired setting, what is the risk of losing data due to a power outage.Dave
Generator for the building + UPS for the servers = 0 dataloss due to power outage.  Daniel, MCP, A+SQL Server DBAwww.dallasteam.com |
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Michael Valentine Jones
Yak DBA Kernel (pronounced Colonel)
7020 Posts |
Posted - 2005-10-26 : 16:19:23
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| "Generator for the building + UPS for the servers = 0 dataloss due to power outage."So you feel that all of the the following would be impossible if you have a building generator and UPS?1. Someone turns off the power switch.2. Someone accidentally disconnects the power cord.3. A circuit breaker fails4. Someone turns off the circuit breaker.5. The servers internal power supply fails.As a general rule, risk is never zero.CODO ERGO SUM |
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MichaelP
Jedi Yak
2489 Posts |
Posted - 2005-10-26 : 17:21:51
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| Make sure that your controller cache is battery backed up. Usually, there's a little battery on the SCSI controller or a big battery backup for SAN devices in the disk controller unit. In the bigger boxes there's usually redundant batteries as well.So, you have shore power --> UPS --> Disk Controller Battery --> loss of disk IOMichael<Yoda>Use the Search page you must. Find the answer you will. Cursors, path to the Dark Side they are. Avoid them, you must. Use Order By NewID() to get a random record you will.</Yoda> |
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MichaelP
Jedi Yak
2489 Posts |
Posted - 2005-10-26 : 17:26:09
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| As far as your cache settings, it depends on what sort of IO your are doing, and what sort of disk array and controllers you have. Talk to the people you bought it from for the best configuration for your partiuclar combination. Generally, the defaults are a really safe bet. 100% either way is probably the wrong choice.Michael<Yoda>Use the Search page you must. Find the answer you will. Cursors, path to the Dark Side they are. Avoid them, you must. Use Order By NewID() to get a random record you will.</Yoda> |
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Recommended Setting for Controller Cache?