2009/1/7 Ralf Gross <ralf-li...@ralfgross.de>: > Sergio Belkin schrieb: >> 2009/1/7 Ralf Gross <ralf-li...@ralfgross.de>: >> > T. Horsnell schrieb: >> >> Ralf Gross wrote: >> >> > Ferdinando Pasqualetti schrieb: >> >> >> I think you should use /dev/random, not /dev/zero unless hardware >> >> >> compression is disabled in order to have more realistic figures. >> >> > >> >> > This wouldn't be a good idea, /dev/random or /dev/urandom are just too >> >> > slow in generating random data. To test the nativ speed of the drive >> >> > creating a file from /dev/urandom and writing this file then from >> >> > tmpfs or a fast disk to the drive would be much better. >> >> > >> >> > >> >> > Ralf >> >> >> >> Personally, I'd use /dev/zero with compression turned off. >> >> Then there's *nothing* between the data-source and the tapedrive. >> > >> > Yes, but most people use hardware compresion with LTO drives. Sooner >> > or later he has to test the drive with compression. >> > > > Please always respond to the list...
OK, sorry, I am subscribed to many lists, I don't understand why it not working reply... > >> Please look at the output, I've used urandom instead random, why so >> poor performance? >> >> dd if=/dev/urandom of=/dev/nst0 bs=1M count=1000 >> 1000+0 records in >> 1000+0 records out >> 1048576000 bytes (1.0 GB) copied, 231.398 seconds, 4.5 MB/s > > > It's what I wrote above. /dev/urandom is just too slow. You are > measuring the speed of /dev/urandom not the drive. > > Try 'dd if=/dev/urandom of=/dev/zero bs=1M count=1000' and see what > you get if you write to /dev/zero and not /dev/nst0. I bet it will be > about the same speed because /dev/urandom is too slow for this. > > Ralf > You are right: dd if=/dev/urandom of=/dev/zero bs=1M count=1000 1000+0 records in 1000+0 records out 1048576000 bytes (1.0 GB) copied, 227.275 seconds, 4.6 MB/s I want to tell you that I am not using software compression, and I think as I posted earlier based on tapeinfo that tape drive is not using hardware compression. Why tape drive has such a poor performance? -- -- Open Kairos http://www.openkairos.com Watch More TV http://sebelk.blogspot.com Sergio Belkin - ------------------------------------------------------------------------------ Check out the new SourceForge.net Marketplace. It is the best place to buy or sell services for just about anything Open Source. http://p.sf.net/sfu/Xq1LFB _______________________________________________ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
