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September 21, 2018

Fine Tune: Storing in Parallel and to Tapes

Does the MPE/iX Store-to-Disc option allow for a ‘parallel store,’ analogous to a parallel store to tape? For example, when a parallel store to tape is performed, the store writes to two or more tape drives at the same time. Is there a parallel store-to-disc option that allows for the store to write to two or more disc files at the same time (as opposed to running multiple store-to-disc jobs)?

Gavin Scott and Joe Taylor reply

Yes, the same syntax for parallel stores works for disk files as well as tape files. I really don’t know if you would get any benefit from this, but if you went to the trouble of building your STD files on specific disks, then it might be worthwhile.

What is the recommended life or max usage of DLT tapes?

Half a million passes is the commonly used number for DLT III. One thing to remember is that when they talk about the number of passes (500,000 passes), it does not mean number of tape mounts.

For SuperDLT tapes, the tape is divided into 448 physical tracks of 8 channels each giving 56 logical tracks. This means that when you write a SuperDLT tape completely you will have just completed 56 passes. If you read the tape completely, you will have done another 56 passes.

The DLTIV tapes (DLT7000/8000) have a smaller number of physical and logical tracks, but the principle is the same. The number of passes for DLTIIIXT and DLT IV tapes is 1,000,000. The shelf life is 30 years for the DLT III XT and DLT IV tapes and 20 for the DLT III.

Our DDS drive gets cleaned regularly. Our tapes in rotation are fairly old, too. However, we are receiving this error even when we use brand new tapes. 

STORE ENCOUNTERED MEDIA WRITE ERROR ON LDEV 7 (S/R 1454)

The new tapes are Fuji media, not HP like our old ones.

John Burke replies:

Replace that drive. DDS drives are notorious for failing. Also, the drive cannot tell whether or not you are using branded tapes. I’ve used Fuji DDS tapes and have found them to be just as good as HP-branded tapes (note that HP did not actually manufacture the tapes). I have also gotten into the habit of replacing DDS tapes after about 25 uses. When compared to the value of a backup, this is a small expense to pay.

07:52 PM in Hidden Value, Homesteading | Permalink

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