Tim Jones
Forum Replies Created
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There’s a difference between spanning tapes and breaking the data stream up to fit on tapes. The key being that the LTFS platforms that support automatic multi-tape operations do the data splitting for you.
Since you are concerned about BRU’s checksumming wasting tape, this type of data splitting also wastes tape since with few exceptions, the data is split into segments based on the “approximate” expected storage size of the tape used. It doesn’t (and really can’t) take into account any compression that occurs while writing to the tape.
Tim
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Tim Jones
CTO – TOLIS Group, Inc.
https://www.tolisgroup.com
BRU … because it’s the RESTORE that matters! -
Simply put, your statement that “the only way to know for sure” is completely restore and then reverify all of the checksums for each file may be fine if you’re dealing with 500GB, but try suggesting that to someone with 57 TB of data.
That’s the part that makes me so concerned with the statement that you made. And calling my concern for our users’ data parochial and outdated was a bit flippant in light of the real volume and time involved in production backup and archival. My perspective is neither parochial nor outdated. On the other hand, the fact that you believe that no verification is required because people that you have spoken with haven’t run into problems, is definitely not a safe position.
Regardless of how new the technology, the device is still mechanical, and mechanical items fail. How many tape devices did you work on during design phases? How many software implementations did you work through from initial spec to finished product firmware to get the drive working just right? How many tape formats did you actually design and deliver? Me? I’ve done all of these things from the original QIC-27 drives to the later side of the LTO designs including numerous QIC, DAT, DLT, AIT, and VXA devices.
And don’t get me started about the number of your alma mater’s product’s tapes that we recovered for customers that had no verification when they were made – there were just no errors reported when they made the backup, so it must have been good, right?
With LTO-6 tapes in the $65 per tape range and no need to worry about over-filling a tape – unlike tar and LTFS, BRU’s 18% overhead is a small price to pay for backups that can be verified with no need to restore the data.
Tim
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Tim Jones
CTO – TOLIS Group, Inc.
https://www.tolisgroup.com
BRU … because it’s the RESTORE that matters! -
[Tom Goldberg] “LTO is very robust – if you archived without errors, the chances are extremely high (one in 10^17th) that your data is all there. The only way to know for sure however is to restore every file and compare checksums.
“This statement just makes me sad…
I invite you all to examine this white paper in relationship to Tom’s error rate figure and the need to restore to verify:
Tim
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Tim Jones
CTO – TOLIS Group, Inc.
https://www.tolisgroup.com
BRU … because it’s the RESTORE that matters! -
Why worry about the size. Let BRU handle the tape swaps and you don’t need to worry about it. Files spanning tapes with BRU is not the same as it was with older backup formats (or LTFS where you CAN’T span). BRU has checks and rewrites to protect both sides of the split.
If you’re worried about losing a file from one side of the split to the other because you’ve physically lost a tape, just keep in mind that losing a tape will lose the file on the lost tape anyway…
Tim
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Tim Jones
CTO – TOLIS Group, Inc.
https://www.tolisgroup.com
BRU … because it’s the RESTORE that matters! -
Goce, which version of BRU PE are you using as this was fixed previously?
Also, your tapes are properly written (even with the version that had exhibited the stall on the second drive’s verification pass). You can always manually run a verification pass on any BRU formatted tape at any time.
And comparing that to LTFS, how are you verifying them at all using StoreOpen?
As for the missing catalogs, are you referring to a catalog for a tape on which the verification pass stalled? That was associated with what was causing the stall. You can always regenerate a missing catalog by importing the tape.
Tim
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Tim Jones
CTO – TOLIS Group, Inc.
https://www.tolisgroup.com
BRU … because it’s the RESTORE that matters! -
One more thought – how did you originally format the tape? By default, compression is enabled, so if your files are (data) compressible at all, you will see the system reporting less data written to the tape.
If you do an
ls -lRon the folder that you copied the files into on the LTFS volume, does the reporting information match the numbers for the same files on your disk?Tim
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Tim Jones
CTO – TOLIS Group, Inc.
https://www.tolisgroup.com
BRU … because it’s the RESTORE that matters! -
From the LTFS Caveats list – item 11:
Do not depend on OS X or Windows system disk tools for information about an LTFS volume. Because system tools like Finder’s “Get Info…”, “du”, and “df” do not have logic for dealing with the compression on an LTO drive or the space lost to file rewrites on an LTFS volume, the values returned will be estimates that will become less accurate as you write more data to an LTFS volume or replace existing files with new versions. While the available space numbers will be correct, if added to the used space in such situations, the resulting value will be less than the actual stated capacity for a tape.
The whole list is available here:
Tim
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Tim Jones
CTO – TOLIS Group, Inc.
https://www.tolisgroup.com
BRU … because it’s the RESTORE that matters! -
You should definitely open a support ticket at https://support.bru.com. The team will get you sorted very quickly.
Tim
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Tim Jones
CTO – TOLIS Group, Inc.
https://www.tolisgroup.com
BRU … because it’s the RESTORE that matters! -
Here’s the link:
Expand the Software Accordion entry.
Tim
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Tim Jones
CTO – TOLIS Group, Inc.
https://www.tolisgroup.com
BRU … because it’s the RESTORE that matters! -
The simplest mechanism would be to create a new Library and then move the old events into that library, removing them from your working library. Next, simply right click and close that library.
Tim
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Tim Jones
CTO – TOLIS Group, Inc.
https://www.tolisgroup.com
BRU … because it’s the RESTORE that matters!