| From: | Greg Smith <greg(at)2ndquadrant(dot)com> |
|---|---|
| To: | AI Rumman <rummandba(at)gmail(dot)com> |
| Cc: | pgsql-general General <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: question regarding full_page_write |
| Date: | 2011-02-17 04:31:06 |
| Message-ID: | 4D5CA48A.4050608@2ndquadrant.com |
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| Thread: | |
| Lists: | pgsql-general |
AI Rumman wrote:
> I can't clearly understand what FULL_PAGE_WRITE parameter is stand for.
> Documentation suggest that If I make it OFF, then I have the chance
> for DB crash.
> Can anyone please tell me how it could be happened?
The database writes to disk in 8K blocks. If you can be sure that your
disk drives and operating system will always write in 8K blocks, you can
get a performance improvement from turning full_page_writes off. But if
you do that, and it turns out that when the power is interrupted your
disk setup will actually do partial writes of less than 8K, your
database can get corrupted. Your system needs to ensure that when a
write happens, either the whole thing goes to disk, or none of it does.
--
Greg Smith 2ndQuadrant US greg(at)2ndQuadrant(dot)com Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.us
"PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books
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