Elena, I was just replying to myself when your email came in. I knocked up a quick wrapper to enable testing of the cache eviction stuff so I'm happy (ish).
However : I'm seeing puzzling behaviour with chunking. Using collective IO, (tweaking various params) I see transfer rates from 1GB/s to 3GB/s depending on stripe size, number of cb_nodes, etc. However, when using chunking with independent IO, I set stripe size to 6MB, chunk dims to match the 6MB, each node is writing 6MB, alignment is set to 6MB intervals and I've followed all the tips I can find. I see (for 512 nodes writing 6MB each = 4GB total) a max throughput of around 150MB/s. This is shockingly slow compared to collective IO and I'm quite surprised. I've been playing with this for a few days now and my general impression is that chunking = rubbish collective = nice I did not expect chunking to be so bad compared to collective (which is a shame as I was hoping to use it for compression etc). Can anyone suggest further tweaks that I should be looking out for to change. (one thing for example that seems to make no difference is the H5Pset_istore_k(fcpl, btree_ik); stuff. I still don't quite know what the correct value for btree_ik is. Ive read the man page, but I'm puzzled as to the correct meaning. if I know there will be 512 chunks, what is the 'right' value of btree_ik? Any clues gratefully received for optimizing chunking. I hoped the thread about 30,000 processes would carry on as I found it interesting to follow. ttfn JB -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Elena Pourmal Sent: 05 April 2011 17:01 To: HDF Users Discussion List Subject: Re: [Hdf-forum] Question re: Howison et al Lustre mdc_config tuning recommendations Hi John, On Apr 5, 2011, at 4:21 AM, Biddiscombe, John A. wrote: >>>> H5AC_cache_config_t mdc_config; >>>> hid_t file_id; >>>> file_id = H5Fopen("file.h5", H5ACC_RDWR, H5P_DEFAULT); >>>> mdc_config.version = H5AC__CURR_CACHE_CONFIG_VERSION; >>>> H5Pget_mdc_config(file_id, &mdc_config) >>>> mdc_config.evictions_enabled = 0 /* FALSE */; >>>> mdc_config.incr_mode = H5C_incr__off; >>>> mdc_config.decr_mode = H5C_decr__off; >>>> H5Pset_mdc_config(file_id, &mdc_config); > > I couldn't find fortran bindings for these. Do they exist in any recent > releases or svn branches. > Fortran wrappers for do not exist. Please let us know which Fortran wrappers do you need and we will add them to our to-do list. Elena > thanks > > JB > > _______________________________________________ > Hdf-forum is for HDF software users discussion. > [email protected] > http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org _______________________________________________ Hdf-forum is for HDF software users discussion. [email protected] http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org _______________________________________________ Hdf-forum is for HDF software users discussion. [email protected] http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org
