Hi Artem!

Artem Trunov wrote:
> Hi, all
> How does xrootd interact with underlying file system? Are there
> tunable parameters? Like blocksize for i/o requests?

  I guess that those tweaks are to be found in the OS. Afaik in xrootd you 
can only tune the size of the subchunks in which a bigger block is to be 
split, but I believe that it's not used in your use cases.

> When a client
> sets readahead parameter, is it effectively a single disk read
> operation? What about writing?

  In single tcp stream mode the client generally does not split blocks, so 
the server gets a ingle request, when you enable the multiple tcp sterams 
instead nearly all the blocks are splitted in various subchunks, so it's not.

  For writes xrdcp/XrdClient applies the same algorithm.

> Also xrdcp - the same questions - is it possible to tune disk i/o?

  When writing to the local disk? No, it writes what the server sends in 
4M/8M blocks, trying to make them sequential. The only parameters are those 
in the OS filesystem config.


> cheers
> Artem.