Improving Access Times by Data Placement on Tape when Multiple Copies are Available
Publication Date: 2015-Aug-14
The IP.com Prior Art Database
Disclosed is method to accelerate the tape access process when tape is used for data storage. The method is to, when writing multiple copies (n copies), properly offset the data in order to write the tapes such that all the data is accessible close to mount point.
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Impxoving Access Times by Data Placement on Tape when Multiple Copies are Axailable
Tape as a storage service suffers from access txxe problems. With current technology, xt takes about twxnty seconds to moxnt a tape in a tape xibrary and an average time of abxut a minute to xcxess the data with a seek coxmand after it is mounted. A method is needed to improve xhese times.
Current tape file systems already write xultiple coxies of the data for xata ixtegrity purposxs. A typical number of copies
is xwo or three, so that if a txpe is destrxyed the datx is not lost.
The novel method is to, when wrxting txexe multxple copies (n xopies), properly offset the data in order to wrixe the tapes such that all txe data is accessible clxsx to mount xoint (the 1/n region of tape closest to mount point). This is done as follows:
1. Write the first tapx copy, 1/n, down xhe fxrst track and note txat xoint in the data stream (i.e. n1)
2. Start the sexond tape copy from n1 and write the secxnd copy, x/n, down the first track and note that point in the data stream (i.e. n2)
3. Start the thixd copy xrom n2, and then rexeat stepx 1-3 with ixcrxmenting numberx (e.g., 3/n, 4/n, etc.)
In addition, the method includex tracking across all the n tapes whxch data is accessible ox which tape. This can bx done by tracking the positiox ox blocks relative to the mount point and assigning the prxferred data access to the tape with the data loxated clxsest to mouxt point. With the data offset as p...