explain xkcd - User contributions [en]

Talk:1718: Backups

2016-08-12T09:50:27Z

Epaminaidos:

I think this makes more sense if only a small portion of all files from the laptop complete the ENTIRE loop. if the total percentage of files which complete the entire loop is 0.0004% , and he backups once a month, that should give him exponential growth slightly smaller than Moore's Law. At 18 months, his total file size would be about 168% of the original. [[Special:Contributions/172.68.58.245|172.68.58.245]] 22:03, 10 August 2016 (UTC)
: "Cueball: Wait. My laptop is backing up some folders to this server..." Because of that I agree with you. It's saying "Some" folders are being backed up. The wording heavily implies it's not everything in the computer being backed up just a part. [[Special:Contributions/141.101.98.61|141.101.98.61]]

Also, the title text my refer to that often when you lose a project and have to start over from scratch, the project become so much better. [[Special:Contributions/162.158.133.102|162.158.133.102]] 01:55, 11 August 2016 (UTC)



This happens. It can really surprise you when the exponential curve is flat enough. We had a case where we kept a log of the backups on a server that was backed up. This went fine for years, until at some point when we ran out of backup space we found that backups of the logs of backups consumed over 99% of our diskspace.[[Special:Contributions/162.158.87.11|162.158.87.11]] 10:04, 11 August 2016 (UTC)
:Tee hee! This is why the first thing I exclude from backup is the log directory, or the whole /var tree (with a few selected exceptions, like /var/spool/cron/crontabs - this is a royally misplaced location, it should go under /etc). The logs that need to be kept are sent to a log server, online, by the logger daemon itself. If there's no log server (small systems) at least send the logs to backup place during log rotation. -- [[Special:Contributions/162.158.203.151|162.158.203.151]] 18:59, 11 August 2016 (UTC)
:I once managed to backup / to the backup disk at /media/Backup Disk. D'oh. Backupception. --[[Special:Contributions/162.158.150.228|162.158.150.228]] 12:17, 11 August 2016 (UTC)

I think there should be an explanation, why this setup leads to exponential growth. IMO, it is linear or polynomial of degree 2 at most. Let's assume, the notebook does only contain one file: /A.txt. After one backup-cycle there are two files: /A.txt and /backups/A.txt. After the next one, there are three: /A.txt, /backups/A.txt and /backups/backups/A.txt. Thus the amount of files does only grow in a linear way. Only the path-information is growing faster: The amount of additional directories in the file's path is growing with the square of the amount cycles (it's the sum of all integers from 1 to the cycle-count).
Can anybody explain the exponential growth? [[User:Epaminaidos|Epaminaidos]] ([[User talk:Epaminaidos|talk]]) 06:44, 12 August 2016 (UTC)

: The number of files grows exponentially, if not a certain amount of data but a percentage of the data is backed up in each cycle. --[[Special:Contributions/162.158.83.228|162.158.83.228]] 07:31, 12 August 2016 (UTC)
:: Can you elaborate this? I don't get it. [[User:Epaminaidos|Epaminaidos]] ([[User talk:Epaminaidos|talk]]) 09:50, 12 August 2016 (UTC)

: I guess most backup systems keep older backups. First, there's /A.txt. Next, there's /A.txt and /backup/2016-08-12/A.txt. Third, there's /A.txt, /backup/2016-08-12/A.txt, /backup/2016-08-13/A.txt and /backup/2016-08-13/backup/2016-08-12/A.txt. --[[User:SlashMe|SlashMe]] ([[User talk:SlashMe|talk]]) 09:38, 12 August 2016 (UTC)
:: Cueball is talking about "syncing folders", not about a backup-system that keeps old versions. [[User:Epaminaidos|Epaminaidos]] ([[User talk:Epaminaidos|talk]]) 09:50, 12 August 2016 (UTC)

Talk:1718: Backups

2016-08-12T06:44:15Z

Epaminaidos:

Talk:1522: Astronomy

2015-05-08T09:58:10Z

Epaminaidos:

For a telescope you can be far away, for a magnifying glass or microscope you need a ladder to be nearer to the stars. Microscopes are for biology, telescopes for astronomy.
They have got a similar purpose, but look and are applied differently. Sebastian --[[Special:Contributions/108.162.254.122|108.162.254.122]] 07:09, 8 May 2015 (UTC)

Seemed like another example of Beret guy contradicting how things work, like how he blows into the power cord and inflated a computer, or how he plugged a cord into a power outlet labeled "COFFEE" and coffee came out. [[Special:Contributions/108.162.238.168|108.162.238.168]] 07:19, 8 May 2015 (UTC)
:Yes obviously this approach works for Berret Guy because this is what he does. Explanation lacks this fact. --[[User:Kynde|Kynde]] ([[User talk:Kynde|talk]]) 07:44, 8 May 2015 (UTC)
:Soup, wasn't it? But yes, for some reason he can actually use a stepladder to get a closer look (and a better one, thanks t the magnifying glass) on the "curtain of the night", which for him ''is'' actually within reach. As if it is just like a stage back-cloth with some form of star-effect (holes and backlight or sewn-in LEDs) as far as he is concerned.
:But what I was actually coming here to say was regarding Astrobiology being a portmanteu (as currently in the explanation). I'm not sure I'd call it that. It's really a perfectly normal compound description of a study area, like many others in science, used to clarify what ''subset'' of biology it is (e.g. paleobiology being the biology of historic organisms, more or less, coming roughly from the greek for "old life study"). Although it does rather hint at it's "the biology of stars themselves", as opposed to the perhaps more accurate exobiology ("outside life study") when it comes to off-Earth life not in (or being) actual stars; or xenobiology ("strange life study"), although that does tend to include oddments of obscure Earth biology and artificial life as well and really doesn't mean the study of extra-terrestrial organisms... [[Special:Contributions/141.101.98.186|141.101.98.186]] 08:00, 8 May 2015 (UTC)
:: Astrobiology is a perfectly normal word. http://en.wikipedia.org/wiki/Astrobiology. [[Special:Contributions/173.245.54.151|173.245.54.151]] 08:49, 8 May 2015 (UTC)

A minor comment on the incorrect use of the word ''portmanteau'' in the explanation so far: it is defined as [http://www.thefreedictionary.com/portmanteau a word formed by merging the sounds and meanings of two different words], [[wikipedia:portmanteau]]; however, [http://dictionary.reference.com/browse/astro- astro-] is a combining form of the the greek word ''aster'' meaning ''star'', used to form compound words, such as ''astro-bio-logy'' (aster-bios-logos: star-life-word). See [[1485]] for an example of the correct use of ''portmanteau''. (someone beat me to it while i was editing this ;-))
[[Special:Contributions/141.101.104.161|141.101.104.161]] 08:07, 8 May 2015 (UTC)
:Thank you. --{{User:17jiangz1/signature|09:14, 08 May 2015}}

You could view the comic as a theatrical production, Megan's telescope as a prop, and Beret guy is just inspecting the backdrop. The ladder is for comic and aesthetic effect {{unsigned ip|141.101.99.53}}

Aaaaa. Astronomers do not touch telescopes while observing. [[Special:Contributions/173.245.52.185|173.245.52.185]] 09:23, 8 May 2015 (UTC) Cameron

My first association was the Hubble Space Telescope: Even though there are huge telescopes on earth, most (all?) of them are inferior to the relatively small telescope a few km above earth's surface. Beret Guy could have tried to achive the same effect by climbing a ladder. [[User:Epaminaidos|Epaminaidos]] ([[User talk:Epaminaidos|talk]]) 09:58, 8 May 2015 (UTC)