On 11/09/16 10:56, Alan Brown wrote: > On 09/11/16 14:17, Ralf Brinkmann wrote: >> I just checked the use of the multicore compression program "gzip" on >> one file-daemon side. It did use 32 cores out of 48 possible. >> >> I think even for LTO tape drives the use of a multicore compression tool >> could be a win on time and storage space. > Be sure that that your "48 cores" really are physical cores - > hyperthreading is of no use when running gzip processes and using more > pigz threads than there are physical CPUs will result in performance loss. > > Pigz -9 will normally get you 5% extra over the onboard hardware > compression on a LTO drive, with a massive computational cost - and you > have the extra cost of getting the data in from a PCIe bus, processed > through the CPU(s), and out through another PCIe bus, with the overall > penalties meaning it's simply not worth doing it.
Also consider that LTO drive hardware compression is smart. When it receives a block to be written to the tape, it makes a compressed copy of the block, compares the size of the compressed and uncompressed blocks, and writes *whichever is smaller* to tape. Software compression on the host does not do this. Really, LTO compression is so good that there is no defensible reason not to use it. -- Phil Stracchino Babylon Communications ph...@caerllewys.net p...@co.ordinate.org Landline: 603.293.8485 ------------------------------------------------------------------------------ Developer Access Program for Intel Xeon Phi Processors Access to Intel Xeon Phi processor-based developer platforms. With one year of Intel Parallel Studio XE. Training and support from Colfax. Order your platform today. http://sdm.link/xeonphi _______________________________________________ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
