Time Machine, how it works?

Discussion in 'Mac Basics and Help' started by Makboy, Mar 2, 2017.

  1. Makboy macrumors newbie

    Mar 2, 2017
    Hi, I have an iMac 27" with 1Tb HDD, and one WD 1Tb external USB drive using about 600gb, I need to back up those 600gb that are on the external drive, today I purchased another WD 1Tb external USD drive to use for backing up those files only, but looking on the internet it looks that TM doesn't back up files from an External HDD to another External HDD? how can't it be? is TM that bad?

    So I've 2 options:

    Option 1) using the new external HDD to back up the files that are on the used External HDD using another app instead of TM? (if so, which one could do this?)

    Option 2) returning the new 1Tb HDD I bought and get a 2Tb of capacity and use it for back up the internal iMac HHD plus the External HDD, can I use TM for this?

    Please help, I really need to back up those 600gb that are on my External HDD to another External HDD, much appreciated any suggestions!

    I'm amateur with back up, it would be the very first time doing this, and I'm Mac user for about 20 years!!! I know, bizarrreeeeeee.! :)

    I appreciate to get an answer asap please in order I have time to return and change the 1Tb HDD to 2Tb if it worth backing up everything!! thanks!
  2. Mikael H macrumors 6502a

    Sep 3, 2014
    Open the Time Machine preferences, click Options and remove the external drive you want to backup from the exclusion list.
    It's not a bad idea to backup your internal drive too, so get the bigger drive anyway, but for your purpose there's really nothing wrong with TM.
  3. Makboy thread starter macrumors newbie

    Mar 2, 2017
    Thanks Mikael, I see, just a couple of more questions:

    1) this is the very first time doing this, so how does the back up work? Every time I save a new file on my external drive (ie. a big PSD photoshop file) does TM copy that file immediately into my new external drive? does it slow my machine? or you can set the back up time for example at evening when I'm not using the computer?

    2) creating the back up encrypted has any cons? I mean does it slow the machine or if I want to move, recovery or delete files will take a longer process?

    3) does TM keeps EVERYTHING? I mean everything, for example if I delete some heavy PSD files or files I don't use, will TM delete those files as well? is it like a mirror? or does TM will keep those files anyway.
    Just asking this because I could reduce space first by deleting the files I don't use anymore and then create the back up if you know what I mean...so I should be deleting files first? then back up the drive...

    thanks again, it is very important for me. :)
  4. satcomer macrumors 603


    Feb 19, 2008
    The Finger Lakes Region
    The first time you make a Time Machine backup it backs up the WHOLE drive and that takes time! That's why some experienced Mac users say the first backup should be a wired backup and after that is done go wireless. After that Time Machine will just make incremental changes.

    I use it to get old files using the Time Machine software that I need and use that software to 'restore' the files.

    If you want more granular control of Time Machine look at the free software Time Machine Editor.
  5. Ebenezum macrumors 6502a

    Mar 31, 2015
    If the iMac has Core i5 or i7 processor it probably won't slow the machine because the processor supports encryption but keep in mind that if you forget the password or recovery key you can kiss your data good-bye...

    Time Machine only keeps the files if they exist in the original disk. I wouldn't recommend using it for archival purposes because you could surprised nastily in one day...

    I'm not saying that you can't use Time Machine but it has had its share of the bugs in the past. If your data is very important I would recommend making another backup with some other software to another drive. By doing so you will minimise the risk of data loss (Time Machine bug won't effect another backup software).
  6. ApfelKuchen macrumors 68030

    Aug 28, 2012
    Between the coasts
    Yes, Time Machine keeps EVERYTHING.

    Yes, you can save space in the first Time Machine backup you make by cleaning house prior to making that first backup. However, once that first backup has been made, it keeps EVERYTHING added or deleted from that day forward.

    Time Machine keeps a snapshot of the current state of the machine each time it backs up. This is what allows you to go back in time - you can go back to any stored snapshot and you'll see things just as they were. Let's say you started making Time Machine backups last week. Then, you delete one of those PSD files today. It will not be present in the Today snapshot. However, it will be present in yesterday's snapshot. If you edited that file yesterday, and you also edited it the day before yesterday, you'll have access to both versions of the edit by going back to the desired date.

    Now, those snapshots are just records of the condition of the system. In addition to the snapshots, Time Machine, of course, saves the files. It keeps only one copy of each version of the file - so, say you made your first backup last week, and you haven't changed a particular file since then. There will be just one copy of that file in the backup, but it will be listed in every snapshot, and you can retrieve it from any snapshot.
  7. Mikael H macrumors 6502a

    Sep 3, 2014
    1. As @ApfelKuchen wrote, the first time you create a backup, everything gets backed up. After that, you get periodic backups of the changes since the last backup, just as it says in the Time Machine preferences window: Hourly backups for a day, daily backups for a month, and weekly backups for as long as you have room on the backup disk, at which point TM deletes the oldest data.
    Since it creates only backups of the changes, they aren't very resource-intensive, and you probably won't notice them a lot. If you do need all the I/O capacity of your Mac for a short while, you can just disconnect the backup drive while you do, and then reconnect it, and it will resume backups automatically.

    2. Creating encrypted backups requires a bit more of your machine, but may definitely be worth it if you are afraid of data theft.

    3. TM keeps what you haven't put in your exclusion list for as long as it has room for it. TM is NOT an archive software - things you delete from your computer will eventually disappear from your backups as your backup disk fills up! If you have data you no longer use but want to retain, you'll need to archive it in a safe way. If you have scrap data you don't need backups of, put it in a directory you add to the exclusion list.
  8. ApfelKuchen macrumors 68030

    Aug 28, 2012
    Between the coasts
    Mikael H's points are spot on, but the longevity issue can easily be addressed - Time Machine only deletes the oldest backups if it runs out of disk space. It's completely possible to migrate to a larger backup drive if you need to.
  9. Mikael H macrumors 6502a

    Sep 3, 2014
    One thing I haven't looked up is whether it's possible to migrate an encrypted backup. It may be that moving those files will break some cryptographic checksum. I don't know whether this is the case, but I just wanted to state this word of caution.
    If migrating an existing backup is not possible, it's always possible to retain the old drive and get a new one.

    However I stand by my earlier statement: Backups are great, but don't ever confuse backups with an archive, especially if you have only a single backup medium. Disks will fail sooner or later if you use them continuously, and they will fail if you don't use them for extended periods of time. Having multiple backups plus archive solutions is usually overkill for someone not living off their data, but if something is truly important to you, invest in archive grade tape, storing one copy with someone you truly trust, or pay a professional archive company to keep that data safe.
  10. Makboy, Mar 3, 2017
    Last edited: Mar 3, 2017

    Makboy thread starter macrumors newbie

    Mar 2, 2017
    WWOOOOOOWWW thank you very much!!! I have now to think a lot about it, I didn't realise the fact that TM is not an archive software!
    --- Post Merged, Mar 3, 2017 ---
    Thanks a lot, but does it mean if I save a PSD in 3 different days I would have same PSD file X3? so this action will be using the drive space capacity? is there any chance, for example, to keep the back up for the last 2 months forward, so it means if I was dealing with a heavy PSD several times after 2 months I will keep the final one and the rest will be erased? is that how it works?
  11. Mikael H macrumors 6502a

    Sep 3, 2014
    No, sorry. TM makes backups of anything not in the exclude list, and keeps them for as long as possible. That's it.

    What you need to do is to ensure that a disk you use as a backup medium has enough space to store data for as long as it may be relevant. This is usually not very expensive unless you work with video.

    The example you gave would be a possible use case for some external disk solution or file server, if you lack space on your Mac. That quickly becomes expensive, though, because it needs to be fast enough so you actually use it for storing work data, and it too will need to be backed-up somewhere.
  12. ApfelKuchen macrumors 68030

    Aug 28, 2012
    Between the coasts
    Archive and backup can be two separate things, or one and the same - it depends on your particular needs.

    An archive is not necessarily off-site/off-machine storage - it's an organized record that can be anywhere, including the internal HDD. The contents of the archive will vary, depending on many factors. It's very possible that you'd want to make a backup of an archive, no matter where it resides.

    Backup is, first and foremost, disaster recovery. We think in terms of the big disasters first - total loss of the contents of an HDD. A whole-disk/whole-machine backup makes it easier to recover from disaster - just restore the backup to the new HDD. That's far less labor-intensive than trying to reconstruct the contents of the machine piecemeal.

    Partial "backups" (saving only the files you think are important to you) almost always results in what I'd call a "Big Yellow Taxi situation" (from the Joni Mitchell song... "Don't it always seem to go, that you don't know what you've got 'til it's gone!").

    Time Machine, like other incremental backup solutions, can resemble an archive - the ability to retrieve a single item from a particular date and time. Its user interface is designed to make that kind of individual file recovery as easy as possible. However, I like to look upon that as an added benefit, rather than its primary reason for existence.

    You'll see lots of talk about using Carbon Copy Cloner (CCC) instead of, or as a supplement to, Time Machine. If you use CCC to make periodic, whole-machine backups while leaving Time Machine to do the incremental backups, it seems like a pretty good strategy. Restoring a whole-machine CCC disk image is very fast and straightforward if/when you need to do it. Restoring from any incremental backup (and CCC can also be used for incremental backup) will be more time-consuming, as the restore software has to reconstruct a final result from multiple backup sets. An incremental restore may have a greater risk of error since, with more "moving pieces," there's greater likelihood that one or more pieces may be missing. On balance, I prefer the up-to-date coverage of an incremental backup to the spottier coverage of, say, a week-old (or older) full backup.

    automated backup system can fail, for any number of reasons. I don't know that an automated, incremental backup in CCC is any more reliable than a Time Machine backup, but I have no statistical info to back that up. The benefit of automated backups, of any sort, is that they're far more reliable than, "I'll remember to run a manual backup every day/every week." There are practical limits to how many whole-machine backups you'd keep, considering their size. While you may never need to go back more than a few weeks in time, if you feel that going way back in time may be useful for you, Time Machine is a far more economical approach.

    If large external HDDs were expensive, that'd be one thing, but they're not. The usual rule of thumb for Time Machine external drive capacity is three times the capacity of the drive being backed up. So, a 1 TB internal drive should be backed up by a 3 TB external (that can be less than $100 at today's prices). It may be a very long time before you exceed that 3x capacity. I've been using my primary Mac for about 3 years. There's 1.1 GB on the 3 TB internal drive, the 3-year-old Time Machine backup size is 1.49 TB. Your mileage, of course, may vary.

    I can appreciate the concerns that Time Machine may end up saving dozens of copies of the same file over the course of time (presuming you give that much attention to a single file), but the vast majority of files you work on are not going to get that kind of attention, are they? If they're works-in-progress for clients, one hopes that you're making enough to cover the cost - the time you may save retrieving even one of those interim versions may be worth the cost of storing interim copies of all your files. Further, since Time Machine consolidates backups over time (discarding hourly backups in favor of a consolidated daily backup, discarding dailies in favor of a consolidated weekly backup, etc.), many of those saved, interim versions of files will be discarded eventually, automatically.
  13. Makboy, Mar 4, 2017
    Last edited: Mar 4, 2017

    Makboy thread starter macrumors newbie

    Mar 2, 2017

    Hi, thanks a lot for a full detailed response!, I live in Argentina where economy su***, $100 dollars I paid for WD 1Tb disk, if I go for 2tb about $160, I think they don't even sell 3tb external disk so I'm very limited.
    I'm graphic designer, sometimes have to handle 200mb PSD, I don't want a new file backed up just because I did a small change on Photoshop the next day, it sounds like "I'll eat your whole HD soon...".

    At the moment I'm using 600gb of an external drive (1tb) and wanted to back up those files, that's why I was "happy enough" to buy a new 1Tb external drive for back up, but after reading all the replies I see is not that simple as I thought, even when you say that TM back ups EVERYTHING, even the disks that are excluded?? (ie. internal HDD) so 1tb won't be enough I'm afraid.

    I wouldn't need the "old files" that were changed if you know what I mean because they are not useful anymore.
    Unless as user Satcomer said, to use TM Editor in which I could set back ups say every month?, so does it mean within the month TM won't backup anything? if so, this would be a solution because TM won't make back ups every day, so at the 1st day of every month TM would back up what's on the external drive in that moment? is that how it works?, if I can do this it'd be great, so I can save lot of space.

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12 March 2, 2017