On Tue, Nov 17, 2009 at 03:34:59PM +0000, Steve wrote: > Alex Betis wrote: > >I don't record much, so I don't worry about speed. > > While there's no denying that RAID5 *at best* has a write speed > equivalent to about 1.3x a single disk and if you're not careful with > stride/block settings can be a lot slower, that's no worse for our > purposes that, erm, having a single disk in the first place. And reading > is *always* faster... > > Example. I'm not bothered about write speed (only having 3 tuners) so I > didn't get too carried away setting up my 3-active disk 3TB RAID5 array, > accepting all the default values. > > Rough speed test: > #dd if=/dev/zero of=/srv/test/delete.me bs=1M count=1024 > 1073741824 bytes (1.1 GB) copied, 13.6778 s, 78.5 MB/s >
You should use oflag=direct to make it actually write the file to disk.. > #dd if=/srv/test/delete.me of=/dev/null bs=1M count=1024 > 1073741824 bytes (1.1 GB) copied, 1.65427 s, 649 MB/s > And now most probably the file will come from linux kernel cache. Use iflag=direct to read it actually from the disk. -- Pasi > Don't know about anyone else's setup, but if I were to record all > streams from all tuners, there would still be I/O bandwidth left. > Highest DVB-T channel bandwidth possible appears to be 31.668Mb/s, so > for my 3 tuners equates to about 95Mb/s - that's less than 12 MB/s. The > 78MB/s of my RAID5 doesn't seem to be much of an issue then. > > Steve > > > > _______________________________________________ > vdr mailing list > vdr@linuxtv.org > http://www.linuxtv.org/cgi-bin/mailman/listinfo/vdr _______________________________________________ vdr mailing list vdr@linuxtv.org http://www.linuxtv.org/cgi-bin/mailman/listinfo/vdr
