Donny Cooper wrote:>
> It''s my understanding that Lustre is NOT buffer nor page cached on
the
> Client, which makes perfect sense for a distributed shared resource.
> But is Lustre buffer and page cached in the MDS & OST memory,
> respectively?
You will be surprised to learn that it''s the other way around.
Lustre makes extensive use of the page cache on client nodes, which is
required for high I/O rates. Only by keeping enough I/O in progress at
all times are we able to keep the pipelines (network, software, disk)
full. Our distributed lock manager protects the state of these caches,
which guarantees that applications will never see out-of-date or invalid
data.
On the object storage server, we take great pains to avoid using the
page cache, because it only slows us down and causes headaches. Lustre
uses ext3 in the backend for the disk file system, which will make some
use of the buffer cache on the MDS and OSS.
Hope that helps--
-Phil