Re: read-ahead in NFS server

[Jeff Garzik <jeff@garzik.org>]

saeed bishara wrote:
>> (linux-nfs added to cc)
>>
>> I cannot speak for the NFS server code specifically, but 32kb sounds
>> like a network read (or write) data size limit.
> yes
>> Are you using TCP?  Are you using NFSv4, or an older version?
> I'm using NFSv3/UDP.

IMO, you definitely want TCP and NFSv4.  Much better network behavior, 
with some of the silly UDP limits (plus greatly improved caching 
behavior, due to v4 delegations).


> I found that the actual requests size was 16KB, after doing some hacks
> in server&client I managed to make it 60KB, now I see better
> performance, and I see that the average request size is ~130KB which
> means that there is actually read-ahead. but why it's only 130KB? how
> can I make it larger?
> when I run local dd with bs=4K, I can see that the average IO size is
> more than 300KB.

Read-ahead is easier in NFSv4, because the client probably has the file 
delegated locally, and has far less need to constantly revalidate file 
mapping(s).

	Jeff