Chapter 4 – Configuring nTier File Migrator
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To overcome this, File Migrator implements a data pipeline that allows the
application to continue writing data to the next file before the last file is
completely written to tape. Selecting the
Force applications to wait...
option turns
off the data pipeline, forcing applications to wait until the data has been written
to the tape drive before they can continue. With some applications, this may
lead to slightly improved data integrity at the cost of a loss of system
throughput. Some applications may be incompatible with this option and may
not function at all with the option selected. The degree of these effects is highly
application dependent, and system administrators who want to explore the
effects of this option are advised to experiment with non-critical data.
Archive file fragments as soon as they are available.
In normal operation, a file’s
data is written to tape after it has been successfully written to magnetic disk.
Some application types, for example certain backup applications, can create
very large files that are written sequentially—that is, the application starts to
write data at the beginning of the file and proceeds linearly through the file,
gradually extending it as more data is written. In this situation it is more
efficient to write data to tape as soon as the application has finished writing the
first fragment, rather than waiting for the application to write the entire file. To
do this, enable file fragmentation (see Step 4 on page 57) and select the
Archive
file fragments...
option.
Force the first read of a file after it is written to come from the archive, so that the
integrity of the archive may be checked.
Some applications employ a read-after-
write check to verify the integrity of data written to the archive. However, the
normal behavior of the system is always to read data from the location that will
provide the data the fastest. For data that has just been written to the system,
this usually is the magnetic disk cache or even an intermediate RAM cache.
Performing a read-after-write check then checks the integrity of the data in the
cache, rather than on the tape.
The
Force the first read of a file after it is written...
option forces data to be read
from the tape, even if it is available from an intermediate cache, thereby
allowing applications to verify the integrity of data on the tape. Note that only
the first read is forced to come from the tape; subsequent reads are satisfied
from the cache if possible.
Make files read-only.
This option forces all files in the file group to be marked
read-only. This read-only attribute cannot be changed after a file has been
created.
3.
When you have selected all of the desired Advanced options, select
Ok
to save your
changes. Select
Cancel
to discard changes you made.
