Hi there
In my organisation we have a solaris network with /home being automounted from /export/home on a central file server (usual stuff) however, the guy who originally set this up only allocated 3gb to /export/home and now we are really struggling for space. I have a new 18gb disk installed... (3 Replies)
Hi, Im trying to take a database backup. one of the files is 26 GB. I am using cp -pr to create a backup copy of the database. after the copying is complete, if i do du -hrs on the folders i saw a difference of 2GB.
The weird fact is that the BACKUP folder was 2 GB more than the original one!
... (1 Reply)
Dear All,
Could you please help me to split a file contain around 240,000,000 line to 4 files all equally likely , note that we need to maintain that the end of each file should started by start flage (MSISDN) and ended by end flag (End), also the number of the line between the... (10 Replies)
We have 3 Unix servers all running SVR4 Unix 1.4. I have no problems copying files to and from 2 of the servers using either the rcp command or ftp but when i come to transfer large files to the third server the copy gives up part way through and crashes this server. Copying smaller files using RCP... (7 Replies)
Hi,
I have a process which duplicates files for different environments. As the files arrive, my script (korn shell) makes copies of them (giving a unique name) and then renames the original file so that my process won't get triggered again.
I don't like it either, but it's what we were told to... (4 Replies)
I have a large file that I append entries to the end of every few seconds. Its grown to >150MB. Its basically a log file but a perl script is writing to it. I need to make a copy of it to a new directory. I realize the latest entries occuring while the copy is taking place will not be recorded... (1 Reply)
Hi Forum.
I was trying to search the following scenario on the forum but was not able to.
Let's say that I have a very large file that has some bad data in it (for ex: 0.0015 in the 12th column) and I would like to find the line number and remove that particular line.
What's the easiest... (3 Replies)
Hello, I need to copy a 700GB tape-image file over a network. I want to start the copy process before the tape-image has finished being restored from the tape. The tape restore speed is about 78 Mbps and the file transfer speed over the network is about 45 Mbps I don't want to use a pipe, since... (7 Replies)
Hi,
I have a data file that contains 61 columns. I want to delete all the columns except columns, 3,6 and 8. The columns are tab de-limited. How would I achieve this on the terminal?
Thanks (2 Replies)
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Discussion started by: john2022
1 Replies
LEARN ABOUT DEBIAN
bup-margin
bup-margin(1) General Commands Manual bup-margin(1)NAME
bup-margin - figure out your deduplication safety margin
SYNOPSIS
bup margin [options...]
DESCRIPTION
bup margin iterates through all objects in your bup repository, calculating the largest number of prefix bits shared between any two
entries. This number, n, identifies the longest subset of SHA-1 you could use and still encounter a collision between your object ids.
For example, one system that was tested had a collection of 11 million objects (70 GB), and bup margin returned 45. That means a 46-bit
hash would be sufficient to avoid all collisions among that set of objects; each object in that repository could be uniquely identified by
its first 46 bits.
The number of bits needed seems to increase by about 1 or 2 for every doubling of the number of objects. Since SHA-1 hashes have 160 bits,
that leaves 115 bits of margin. Of course, because SHA-1 hashes are essentially random, it's theoretically possible to use many more bits
with far fewer objects.
If you're paranoid about the possibility of SHA-1 collisions, you can monitor your repository by running bup margin occasionally to see if
you're getting dangerously close to 160 bits.
OPTIONS --predict
Guess the offset into each index file where a particular object will appear, and report the maximum deviation of the correct answer
from the guess. This is potentially useful for tuning an interpolation search algorithm.
--ignore-midx
don't use .midx files, use only .idx files. This is only really useful when used with --predict.
EXAMPLE
$ bup margin
Reading indexes: 100.00% (1612581/1612581), done.
40
40 matching prefix bits
1.94 bits per doubling
120 bits (61.86 doublings) remaining
4.19338e+18 times larger is possible
Everyone on earth could have 625878182 data sets
like yours, all in one repository, and we would
expect 1 object collision.
$ bup margin --predict
PackIdxList: using 1 index.
Reading indexes: 100.00% (1612581/1612581), done.
915 of 1612581 (0.057%)
SEE ALSO bup-midx(1), bup-save(1)BUP
Part of the bup(1) suite.
AUTHORS
Avery Pennarun <apenwarr@gmail.com>.
Bup unknown-bup-margin(1)