[DRBD-user] Raid controller cache module gives DRBD problems

Mark Hunting mark at netexpo.nl
Fri Dec 14 11:09:09 CET 2007


    

>> man fsync
>> man fdatasync
>> man sync
>>
>> wikipedia page_cache
>>   
>>     
> Yes I understand that the page cache can speed things up a lot. But how
> is it possible that when I copy a new file to the DRBD disk the copying
> is much faster than the DRBD link of 100MB/second. To be clear, with
> 'new' file I mean a file that I have never used on the DRBD disk before.
> So it can not be in the cache of the secondary server. Therefore the
> copying should go with a rate of 100MB/second, not faster like it does
> now. Or am I missing something here?
>
> Mark
Oh well I understand the point now. Some operations on the master are
only performed on the page cache, and DRBD is informed later. Is it
possible to turn of the page cache for the DRBD device? My RAID
controllers have their own (battery back-upped) cache, so I'd rather not
use the page cache.

Mark



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