mb@rex.cs.tulane.edu (Mark Benard) (03/18/91)
We are using over-the-counter 8mm tapes, name brands labelled for video use, for backups on a Exabyte-based drive. What is a reasonable upper limit for the number of times these tapes should be used for (1) daily incrementals which are kept only one week and (2) weekly backups which are kept 4 to 5 weeks? -- Mark Benard Department of Computer Science INTERNET & BITNET: mb@rex.cs.tulane.edu Tulane University USENET: rex!mb New Orleans, LA 70118
ghg@en.ecn.purdue.edu (George Goble) (03/19/91)
In article <6700@rex.cs.tulane.edu> mb@rex.cs.tulane.edu (Mark Benard) writes: >We are using over-the-counter 8mm tapes, name brands labelled for >video use, for backups on a Exabyte-based drive. What is a reasonable >upper limit for the number of times these tapes should be used for >(1) daily incrementals which are kept only one week and (2) weekly backups >which are kept 4 to 5 weeks? about 800 passes. --ghg
brogers@auspex.auspex.com (Bob Rogers) (03/21/91)
800 passed exceeds the number that Exabyte recommends by 300 passes. This
number is recommended if they are whole tape passes. If you are using
short passes on the tape this number decreases significantly. We see degradation
in the tape error rates with as few as 20 short passes.
I would be very careful with using the tape this long. Another critical item
is cleaning the tapes every week. If you are using the consumer tape cleaning
cartridge you risk accelerating your head wear.
--
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USPS: Bob Rogers/ Auspex Systems/ 2952 Bunker Hill Lane/ Santa Clara, CA 95054yuping@auspex.auspex.com (YuPing Cheng) (03/22/91)
>number is recommended if they are whole tape passes. If you are using >short passes on the tape this number decreases significantly. We see degradation >in the tape error rates with as few as 20 short passes. > I used a brand new tape, wrote and read 24MB of data, and collected the media ECC retry counts: (Exabyte drive tells you the ECC correction count in its sense data. You should read the data before rewinding the tape.) Passes 0 1 2 3 4 5 6 7 8 9 Write 67 48 54 47 44 45 41 41 45 46 Read 38 35 38 35 33 32 33 29 33 37 Passes 10 11 12 13 14 15 16 17 18 19 Write 35 37 40 48 56 52 63 68 78 76 Read 28 34 31 42 40 39 50 56 61 54 Passes 20 21 22 23 24 25 26 27 28 29 Write 82 104 109 109 105 102 128 111 107 110 Read 70 82 74 84 72 93 78 73 83 93 Passes 30 31 32 33 34 35 36 37 38 39 Write 114 142 141 154 168 166 183 182 206 190 Read 87 110 115 118 140 136 144 142 148 161 Passes 40 41 42 43 44 45 46 47 48 49 Write 224 217 219 235 236 250 261 278 267 283 Read 179 159 172 194 189 190 193 202 200 215 Passes 50 51 52 53 54 55 56 57 58 59 Wrtie 300 325 328 355 367 395 369 388 399 379 Read 223 243 242 263 263 302 268 248 283 274 Notice the number of ECC checks decreases initially to pass #10 and increases steadly thereafter. I wouldn't use the tape more than 50 passes. Yu-Ping Cheng, Auspex Systems Inc. ycheng@auspex.com