das@cirl.UUCP (Dave Steffens) (03/24/86)
We are running Ultrix version 1.1 on a uVAX II with TK50 cartridge tape drive.
When dumping our main filesystem to TK50 tape, we noticed that each cartridge
appears to hold only about 40Mb instead of its rated capacity of 95Mb.
What's going on here?
P.S. The TK50 is **very** slow -- it takes almost 3 hours to put 40Mb of dump
on the TK50 whereas it takes only about 45 minutes to put 40Mb of dump
on our ancient PDP11/34 magtape (Digidata 800bpi 45ips).
--
{harvard,mit-eddie,think}!eplunix!earvax!das David Allan Steffens
243 Charles St., Boston, MA 02114 Eaton-Peabody Laboratory
(617) 523-7900 x2748 Mass. Eye & Ear Infirmarygoldman@ucsfcca.UUCP (Eric Goldman) (03/28/86)
[] In article <257@cirl.UUCP> das@cirl.UUCP (Dave Steffens) writes: >We are running Ultrix version 1.1 on a uVAX II with TK50 cartridge tape drive. >When dumping our main filesystem to TK50 tape, we noticed that each cartridge >appears to hold only about 40Mb instead of its rated capacity of 95Mb. >What's going on here? > >P.S. The TK50 is **very** slow -- it takes almost 3 hours to put 40Mb of dump >on the TK50 whereas it takes only about 45 minutes to put 40Mb of dump >on our ancient PDP11/34 magtape (Digidata 800bpi 45ips). >-- >{harvard,mit-eddie,think}!eplunix!earvax!das David Allan Steffens >243 Charles St., Boston, MA 02114 Eaton-Peabody Laboratory >(617) 523-7900 x2748 Mass. Eye & Ear Infirmary Your problem is that your are dumping tapes using the default blocking factor (10) , and the default tape size (2300). An undocumented "feature" of dump is that you can specify another blocking factor. We have a uVAX II running Ultrix 1.1, and we dump and restore using the maximum blocking factor, 126, and a "large" tape length of 4800. We have crammed > 80 MB onto a TK50, as follows: dump 0ubs 126 4800 /usr There is one major "gotcha," however: restore, as provided in standard 4.2bsd and Ultrix, does not know how to read these 126-blocking-factor tapes! It has a blocking factor of 10 hardwired into the code. Sun has fixed this in their distribution, but we VAX users have to modify the restore source and create a version of restore which can work with these tapes. I took the quick-and- dirty approach and created restore126, which has two lines added to the file, tape.c, (renamed tape126.c), as follows: *** tape.c Wed Oct 16 10:38:24 1985 --- tape126.c Wed Oct 16 10:38:24 1985 *************** *** 12,17 #include <setjmp.h> #include <sys/stat.h> static long fssize; static int mt = -1; static int pipein = 0; --- 12,20 ----- #include <setjmp.h> #include <sys/stat.h> + #undef NTREC + #define NTREC 126 + static long fssize; static int mt = -1; static int pipein = 0; As you can see, I simply changed the hardwired blocking factor, NTREC, from 10 (as defined in the include file, /usr/include/dumprestor.h) to 126. A more elegant solution would read the command line for the b flag, as does dump, and allocate memory appropriately for the blocking factor. Since my quick fix has worked perfectly for several months now (dumps go > 3 times faster, and restores have been quick and error-free), I have not been inclined to do a nicer fix. If you do not have source, I will mail you a uuencoded version of the restore126 binary. Dump, as mentioned, needs no modification, since the b flag is there, albeit undocumented. BTW, you should also use the 126 blocking factor for tar, and you'll really see the TK50 stream: tar cb 126 whatever tar xpb 126 whatever --Eric S. Goldman, M.D. UCSF School of Medicine ARPA: cope.ucsf!goldman@ucsf-cgl.ARPA UUCP: ucbvax!ucsfcgl!cope.ucsf!goldman
jsdy@hadron.UUCP (Joseph S. D. Yao) (03/28/86)
In article <257@cirl.UUCP> das@cirl.UUCP (Dave Steffens) writes: >We are running Ultrix version 1.1 on a uVAX II with TK50 cartridge tape drive. >When dumping our main filesystem to TK50 tape, we noticed that each cartridge >appears to hold only about 40Mb instead of its rated capacity of 95Mb. >What's going on here? The default for dump is to assume size 2300', 1600 bpi, blocking of 10 (*1024), 9-track magnetic tape. This gives us 27600" of tape, with 10240 bytes/tape block, or 6.4" + 0.7" IRG (InterRecord Gap). 27600/7.1 ~= 3887.324 10K blocks, or ~38.87 Mb. Several ways out include (documented) key B to tell it how many K long the tape really is; or (undocumented) key 'c', which sets all the parameters correctly for a cartridge. (Another undocumented key is 'b', to change the blocking factor. Use 'c'.) Let me know whether 'c' also increases your speed/efficiency. [The above formulae assume 1600 bpi 9t => 1 byte/linear bit space.] This is under Ultrix 1.1 on a VAX; I'm assuming similar code for your uVAX II. The kernel code is the same. -- Joe Yao hadron!jsdy@seismo.{CSS.GOV,ARPA,UUCP}