No additional shared memory is needed when making multiple copies.
The ITC part of the process occurs AFTER the data has gone through the
data buffers.
To visualize, consider the process diagram in Appx A of the
Troubleshooting Guide. Draw in another tape drive and another arrow
(labelled Backup Image) from the bptm parent process to the new tape
drive. Notice, no new shared memory.
Actually, if you start using ITC but don't increase the number of
drives or MPX level, you'd actually use LESS shm. This is simply
because you'd be able to run fewer streams at the same time. Of
course, you'd probably use less shm but for a longer period of time in
this case.
I believe that in the formula you mention below 'drives * MPX' is
really just another representation of 'max concurrent streams' - which
is probably a more accurate figure in an ITC environment. But, this
is pretty much academic since the formula is really to calculate the
maximum possible shm you might need, so it remains accurate when when
consider that copies could equal one.
HTH,
L
Fabbro, Andrew P writes:
> My understanding from NB notes I've read is that 4.5 supports in-line
> backup copies. e.g., you backup a client and write the backup to two
> tapes at the same time. The NB release notes say you can do up to 9
> copies at the same time.
>
[text deleted]
>
> - What about shared memory usage? The calculation for NB 3.4 is number
> of data buffers x size of data buffers x number of drives x MPX per
> drive. For a box driving DLT (64512 data buffer size recommended, maybe
> 64 data buffers), it's not a major factor - usually not over 128Mb (say,
> 8 drives at 4 MPX each). With more recent technologies, you want fatter
> buffers, more buffers, and more MPX - easily 512Mb of shared memory,
> maybe more. But I can't imagine all of that is just to drive the tape -
> some of it is network buffering, right? So if I need X kilobytes of
> shared memory for a tape drive, do I need X times 2 for two drives doing
> the same backup in an in-line backup? Or is it more like X times 1.5
> (or whatever)?
>
> Thanks,
>
>
> -drew
> fabbro.andrew AT cnf DOT com <mailto:fabbro.andrew AT cnf DOT com>
>
>
> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
> <HTML><HEAD>
>
>
>
> <META content="MSHTML 5.50.4912.300" name=GENERATOR>
> <STYLE></STYLE>
> </HEAD>
> <BODY bgColor=#ffffff>
> <DIV><FONT face=Arial size=2><SPAN class=569531405-09072002>My understanding
> from NB notes I've read is that 4.5 supports in-line backup copies.
> e.g.,
> you backup a client and write the backup to two tapes at the same time.
> The NB release notes say you can do up to 9 copies at the same
> time.</SPAN></FONT></DIV>
> <DIV><FONT face=Arial size=2><SPAN
> class=569531405-09072002></SPAN></FONT> </DIV>
> <DIV><FONT face=Arial size=2><SPAN class=569531405-09072002>Putting
> additional
> drives needed, etc. aside for a moment, it seems like it could be a good way
> to
> make offsite/disaster recovery backups without the hassle of either
> duplicating
> tapes (which doesn't scale well) or running another full
> backup</SPAN></FONT></DIV>
> <DIV><FONT face=Arial size=2><SPAN class=569531405-09072002>for offsite/DR
> purposes. I assume one could use Pool A for one copy and Pool B for
> another and send Pool B offsite.</SPAN></FONT></DIV>
> <DIV><FONT face=Arial size=2><SPAN
> class=569531405-09072002></SPAN></FONT> </DIV>
> <DIV><FONT face=Arial size=2><SPAN class=569531405-09072002>Some
> questions:</SPAN></FONT></DIV>
> <DIV><FONT face=Arial size=2><SPAN
> class=569531405-09072002></SPAN></FONT> </DIV><SPAN
> class=569531405-09072002>
> <DIV><FONT face=Arial size=2><SPAN class=569531405-09072002>- Has anyone used
> inline copying? How well does it work? </SPAN></FONT></DIV>
> <DIV><FONT face=Arial size=2><SPAN
> class=569531405-09072002></SPAN></FONT> </DIV>
> <DIV><FONT face=Arial><FONT size=2><SPAN class=569531405-09072002>- </SPAN>In
> NB
> 3.4.x, to use a duplicate of a tape, you need to flip it to the primary
> copy. It's easy enough to script - does NB 4.5 work the same
> way?</FONT></FONT></DIV>
> <DIV><FONT face=Arial size=2></FONT> </DIV>
> <DIV></SPAN><SPAN class=569531405-09072002><FONT face=Arial size=2>- What
> about
> shared memory usage? The calculation for NB 3.4 is number of data
> buffers
> x size of data buffers x number of drives x MPX per drive. For a box
> driving DLT (64512 data buffer size recommended, maybe 64 data buffers), it's
> not a major factor - usually not over 128Mb (say, 8 drives at 4 MPX
> each).
> With more recent technologies, you want fatter buffers, more buffers, and
> more
> MPX - easily 512Mb of shared memory, maybe more. But I can't imagine
> all
> of that is just to drive the tape - some of it is network buffering,
> right? So if I need X kilobytes of shared memory for a tape drive, do I
> need X times 2 for two drives doing the same backup in an in-line
> backup?
> Or is it more like X times 1.5 (or whatever)?</FONT></SPAN></DIV>
> <DIV><SPAN class=569531405-09072002><FONT face=Arial
> size=2></FONT></SPAN> </DIV>
> <DIV><SPAN class=569531405-09072002><FONT face=Arial
> size=2>Thanks,</FONT></SPAN></DIV>
> <DIV><SPAN class=569531405-09072002><FONT face=Arial
> size=2></FONT></SPAN> </DIV>
> <DIV><SPAN class=569531405-09072002><FONT face=Arial
> size=2></FONT></SPAN> </DIV>
> <DIV><SPAN class=569531405-09072002><FONT face=Arial
> size=2>-drew</FONT></SPAN></DIV>
> <DIV><SPAN class=569531405-09072002><FONT face=Arial size=2><FONT
> color=#0000ff> </FONT><A
> href="mailto:fabbro.andrew AT cnf DOT com">fabbro.andrew AT cnf DOT
> com</A></FONT></SPAN></DIV>
> <DIV><FONT face=Arial size=2><SPAN
> class=569531405-09072002></SPAN></FONT> </DIV>
> <DIV><FONT face=Arial size=2><SPAN class=569531405-09072002>
> <DIV><FONT face=Arial color=#0000ff size=2><SPAN
> class=569531405-09072002></SPAN></FONT> </DIV></SPAN></FONT></DIV></BODY></HTML>
--
Larry Kingery
You miss 100% of the shots you don't take
|
