On Mon, May 18, 2009 at 7:56 PM, Quanah Gibson-Mount <[email protected]>wrote:
> --On Monday, May 18, 2009 7:55 AM -0700 Bill MacAllister <[email protected]> > wrote: > > However, on BDB 4.7 it seems the default behavior on Linux is also to >>> do synchronous flushes of the cache. As such, one approach to getting >>> consistent performance is to configure the backend to use shared >>> memory for the BDB cache instead of mmap'd files. That way incidental >>> page updates don't sync to anything, and the BDB library has full >>> control over when pages get flushed back to disk. >>> >> >> We can confirm that setting shm_key on 4.7 dramatically affects the load >> time. In our initial tests of 4.7 we just pulled our old 4.2 BDB >> parameters forward. We never saw the slapadd of a 4.6 gbyte database >> complete. We killed it after 4 hours. After changing the shm_key >> setting the load time dropped to the more normal 30 minutes. >> > > > To expand on this slightly. BDB has no difference in perf for small > databases between disk and shm. It's only once your database is past some > 6GB in size that shm vs disk starts to make a difference on Linux. Could someone elaborate on the setting (shared memory instead of mmap) that is best suited for each major OS? Like Linux, FreeBSD, Solaris? > > > --Quanah > > -- > > Quanah Gibson-Mount > Principal Software Engineer > Zimbra, Inc > -------------------- > Zimbra :: the leader in open source messaging and collaboration >
