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Re: [Networker] Why cant I change the browse time on this CFI?
2011-09-21 16:25:07
On 2011-09-21 15:39, Tim Mooney wrote:
In regard to: Re: [Networker] Why cant I change the browse time on this...:
2. I'm unclear on why indexing being turned off for the pool would
preclude you from scanning the tape and adding that information to the
index? Is it the case that if the data was never indexed before then you
can't add it to the index later? Or are you instead referring to using
scanner to recover an index that was never written to tape? That
obviously would not be possible since it was never sent to tape.
The default option 'Store index entries' actually has 2 tasks:
- it generates the CFI metadata and embeds it within the save stream
already at the client.
- it send this info to the CFI at the server in real time.
By disabling it, you already switch of the CFI info generation - it
is logical that there will be nothing to retrieve when you run
'scanner' later. Try it yourself.
What you say makes perfect sense now that I think about it. After all,
how can you recreate index metadata information if you can't determine
what that should be? And having the file(s) on tape doesn't give you
that. Yes, you have the file(s), but what about the user, group,
permissions, etc? All of that original metadata would have to be saved
to the tape, too, which it would not be with the 'Store index entries'
disabled for the pool.
Are you seriously saying that "Store index entries" for a pool conflates
with "don't save any metadata?". That would mean that saveset recoveries
would be pretty useless too, wouldn't it?
Well, if you perform a save set recover then NW should restore the files
with their original time stamps (mod time), user, group, etc., so yes, I
see what you're saying. That information, therefore, would have to be
recorded when the data is written to tape regardless of whether or not
"store index entries" was turned on of off for the pool. So is that
information obtained by NW when it reads the files during save set
recovery, or does it get that information from some other location on
the tape that's separate from the file data itself?
If indexing is turned off then certainly the client file index will not
be updated, but will scanner still be able to build index entries using
the '-i' option? If so, does it actually read the data to get that
information like it might when doing an actual save set recover, or does
it get it in a more efficient way by somehow reading the information
from the end of the save set so it doesn't have to do the time
equivalent of a data recovery by reading every file?
I'm unclear on how the metadata information is stored on the tape, and
if "Store index entries" (yes or no) affects how it's stored on the tape
or where it's stored and whether that would make a difference in whether
or not scanner could rebuild the index and how fast or whether there
would be any difference in speed.
I think the man page on scanner where it talks about the '-i' option is
throwing me off where it says: "Rebuilds". To me that suggests
rebuilding what used to be there, not building what never was?
BUT could NW determine at least the names from the data as it scans the
tape and then build/update the index that would at least have those file
names? Or is it the case that it can't determine the names from the data
on the tape and depends solely on that CFI information having been
written to the tape?
To paraphrase from "The Princess Bride", "I do not think it means what you
think it means."
I've never tried either of the index-related entries you two are
discussing, so perhaps it does mean exactly what you think it means, but
that just boggles my mind.
Tim
--
George Sinclair
Voice: (301) 713-3284 x210
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