Date: Fri, 31 Oct 1997 20:31:20 -0800 (PST) From: Doug White <dwhite@gdi.uoregon.edu> To: Palle Girgensohn <girgen@partitur.se> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: rdump and blocksize? Message-ID: <Pine.BSF.3.96.971031202827.19820Q-100000@gdi.uoregon.edu> In-Reply-To: <34593BC3.41335BA2@partitur.se>
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On Fri, 31 Oct 1997, Palle Girgensohn wrote: > I've been browsing though the mail archive looking for tips on setting a > good blocksize for rdump. My problem is the same as for many others: > rdump is slow, around 48KB/s. > I have checked the network cards, and troughput is very good otherwise > (using for example rcp). Some recommended raising the blocksize, which > seems like the right thing to do. Only, 64 KB is the limit. I don't see > it help very much. Often 10KB or 32 KB were recommended as good values. > > So here's my main quiestion: > Do I have to fine tune the blocksize to some magic value where it's > synced with network & tape drive, or is bigger blocks == faster? I tried > 10 KB, and didn't see any difference. Finding the blocksize is a bit of a black art since it depends on several factors: 1. Disk speed 2. Disk subsystem overhead 3. I/O bus bandwidth 4. Network bandwidth 5. Dump device speed ..... You get the idea. The best thing to do is to try different values and use what works best on your system. > And the -B, is it only for calculating tape usage? Yes. Along with the -b option it specifies the size of the tape. If you're on 2.2.2 or later, you can use the -a option instead to have dump use the tape until it hits the end. > The tape is a Seagate using Travan TR-4, cartridge and compression, so > density is not very interresting, I presume. Its not just interesting, it's irrelevant! :-) Doug White | University of Oregon Internet: dwhite@resnet.uoregon.edu | Residence Networking Assistant http://gladstone.uoregon.edu/~dwhite | Computer Science Major
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