New user setup - only 2 drives, mirror partitions?

  • Hi all,


    Potential new user, looking to setup new NAS build for home. I've had an ubuntu server for a long time (and a couple ubuntu server VMs), but recently I was using my windows box as both a desktop & server. It had 4 drives in it, and I used a couple mirrored for important things (ie family photos), and left the other two for general media file use.
    Looking at what options I had for new build, as from what I've read, it doesn't sound like I could split the two 6TB drives into 2x3TB partitions, and mirror one from each disk? Any way to do something similar in OMV?
    I will consider just re-purposing the current old 4 drives into a backup NAS, but they're fairly old now (>50,000 hours).
    What are my options please?
    Thanks.

  • it doesn't sound like I could split the two 6TB drives into 2x3TB partitions, and mirror one from each disk? Any way to do something similar in OMV?


    You can do but most probably not from the OMV UI in a reasonable way. And since what you plan to do is bad anyway I won't further comment on this since RAID is not backup.


    The idea to 'add some redundancy' if you're in reality looking for data safety/protection is always wrong. If you have important things to store invest time in dealing with backup (concepts) and forget about RAID especially when planning to use the most useless/primitive variants ('Drive mirror' in Windows, Linux mdraid-1 or the crappy 'software raid1' fortunatenly not possible any more in macOS)

    • Offizieller Beitrag

    RAID is not about backup. That's a common misunderstanding.


    If you want true backup, so that you don't lose your irreplaceable data:


    1. The first thing I'd do is estimate the total size of your important files. If the total is less than 6TB, you're in good shape.
    2. Build an OMV server (no RAID) with one of the two 6TB drives as a data drive.
    3. Leave one 6TB drive is the Windows machine, with your critical data on it.
    4. Using Rsync, have your OMV server sync the files and folders on your Windows Client onto your OMV server.
    (Or you could go the other way and use OMV to put your files on your network, as shares, and push / replicate changes to your network shares to your Windows client.)


    The above represents true backup. Either box, the OMV server or your Windows Client could crash and burn and you'd still have another copy of your data. This is NOT the case with RAID in any form where, if something happens to the array, all is lost. Thinking of the old saying, "never put all of your eggs in one basket", it's never a good idea to have a single copy of your data on a single machine. It makes sense if you think about it. Saying that RAID operation is perfect (it's not), if a power supply goes sour, it can cook all the drives in the array.


    If you search this form, you're going to find numerous scenarios where RAID users have lost it all, "thinking that RAID protected them". Given that they learned the lesson the hard way, they tend to be former users of RAID.

  • The above represents true backup.

    Just for the record: unfortunately not even remotely. It's just the try to keep two identical copies of data and that's the opposite of backup (since backup always implements versioning, if the data to be backed up gets damaged or vanished the backup still contains the last version and the version before and the version before if you take care that your backup capacity is large enough).


    Syncing/cloning (rsync) is no backup. You could implement true backup with rsync by implementing 'rsync rotating incremental backup' (do a web search) but in 2017 with at least two non anachronstic attempts available (BTRFS and ZFS --> do snapshots regularly --> send snapshots to a remote location to get physical isolation) it's kinda absurd to still run rsync for such tasks.


    Syncing something from here to there is never backup unless the process implements versioning. Easy to check: on your OMV host do a 'sudo rm -rf /srv/*', then run your rsync task and enjoy data deleted at sync source and destination.

    • Offizieller Beitrag

    Just for the record: unfortunately not even remotely. It's just the try to keep two identical copies of data and that's the opposite of backup (since backup always implements versioning...

    I was simply answering the user's question, in a more relevant manner, rather than make a statement of opinion and leave the question unanswered.


    We could hash back and forth about what backup is and is not, its nuances, etc. But such discussions may never answer the user question that stared the thread, nor guide the user toward a desirable outcome.


    Remember, we're attempting to write to an "audience", not the reflections of ourselves in a mirror. :)

  • Remember, we're attempting to write to an "audience"

    Exactly, that's the reason I enter those 'Hey, some redundancy and everything's fine?' threads from time to time. To prevent people losing data, shift their focus from 'redundancy for no reason' to data safety or even integrity and trying to stop bad recommendations.


    When comparing the 'mirror block devices' or 'sync somewhat around' approaches with a ZFS mirror and a second disk/host with snapshots regularly sent to (unbelievable easy with znapzend for example) this makes a difference like night and day when looking at data protection/safety/integrity. Though not everyone is willing or able to implement the latter. But I will continue to raise these issues just so that the 'hobbyist storage world' still being trapped in concepts from last century hopefully improves :)

    • Offizieller Beitrag

    But I will continue to raise these issues just so that the 'hobbyist storage world' still being trapped in concepts from last century hopefully improves :)

    And I imagine that hobbyist eyes will glaze over from lengthy explanations, devoid of usable practical advice on how to use what is on hand. But, if one must...
    (Perhaps a white paper or a practical guide to inexpensive backup, the way you would do it, might be in order?)


    When we can afford data center hardware in the hobbyist storage world, we hobbyists may achieve something that approaches the official / commercial definition of "backup". Until then we'll be, well, hobbyists. :D
    ________________________________


    In the mean time, with files that are well over 20 years old and nothing lost to date, "replicating data sets around" to independent platforms, on a timed schedule (real time, 1 day, 1 week, and 1to a few months old - in essence "versioning" of 4 complete sets) seems to be working for me.


    Along these lines, the phrase "concepts from the last century" may be overstating things a bit. But if we're journeying into the past, one would have to concede that paintings on the walls of caves, as a form of information storage, has withstood the test of time. Hence, primitive techniques can have their advantages. ;)

  • You can do but most probably not from the OMV UI in a reasonable way. And since what you plan to do is bad anyway I won't further comment on this since RAID is not backup.

    It's bad to store a copy of important files across multiple disks, in case one dies? This I did not know, thanks for educating me.
    I'm aware RAID is not a backup, and never suggested it. I specifically mentioned using the old drives for backup in a separate box (which would likely be offsite at a mate's place), or perhaps just use the cloud for photos.

    I will consider just re-purposing the current old 4 drives into a backup NAS

    For the record, I would consider rsync too. I can't see how that's a bad idea for storing photos, when you just add new ones.
    And for a GUI based OS, hard to see many people running sudo rm -rf from a command line and then rsyncing, but great advice for a test. I'll be sure to try it.

    But such discussions may never answer the user question that stared the thread, nor guide the user toward a desirable outcome.

    This I actually agree with! but ..

    it doesn't sound like I could split the two 6TB drives into 2x3TB partitions, and mirror one from each disk? Any way to do something similar in OMV?

    And since what you plan to do is bad anyway I won't further comment on this since RAID is not backup.

    Lol.


    Never mind, think I'll try a different OS.
    Cheers.

    • Offizieller Beitrag

    It's bad to store a copy of important files across multiple disks, in case one dies? This I did not know, thanks for educating me.I'm aware RAID is not a backup, and never suggested it. I specifically mentioned using the old drives for backup in a separate box (which would likely be offsite at a mate's place), or perhaps just use the cloud for photos.
    For the record, I would consider rsync too. I can't see how that's a bad idea for storing photos, when you just add new ones.And for a GUI based OS, hard to see many people running sudo rm -rf from a command line and then rsyncing, but great advice for a test. I'll be sure to try it.
    This I actually agree with! but ..Lol.
    Never mind, think I'll try a different OS.
    Cheers.

    I can see how this diatribe might be, well, a bit "off-putting".
    In most instances, I think you'd find support to be good in this forum.


    Regardless, I believe you're in the right place. I've tried the other NAS distro's in VM's, poked and prodded them, compared features, ease of configuration, use, etc., and I ended up settling on OMV.
    Other than just straight NAS functionality, OMV's plugins and the ability to easily add DOCKERS makes it stand out. (There are numerous DOCKER / Server add-ons that are simply outstanding.)


    And for your purposes, and mine, rsync'ing file changes between different PC's provides data redundancy.
    (I won't say "backup" and risk kicking it off the debate again! )
    _____________________________________________


    The original case, provided earlier, would work for you. In addition, you could add the smaller disks, maybe using unionfs or lvm to pool them into a single volume, and put data that you're not worried about on them, share them out to the network, etc. But, as old as you say they are, (50K hours), failures should be expected.


    For old drives:
    One of the forum moderators (tekkb) uses a "symlink" approach that I like. (As he states it, as large as modern drives are, the only reason to pool drives in a home environment would be for the storage of video files.) Symlinks work well because, if a single drive fails, only the data that resides on that drive is affected. (Other than the video files lost, the fix is as simple as creating a new link.) While unionfs is nearly transparent in this regard and very good for pooling, other pooling techniques can be a PITA if a drive fails.


    Here's to finding what you're looking for.
    Good Luck.

  • It's bad to store a copy of important files across multiple disks, in case one dies?

    This might protect you from a disk that dies (redundancy providing availability). You mentioned storing 'important things' that's why I answered 'please don't think about redundancy but start to think about data safety instead'.


    More data is lost due to simple mistakes or even ransomware today than by 'disks that died' and this is nothing specific to OMV. If you care about 'important' stuff on your storage then redundancy is a bad concept since insufficient. That's the whole point you're free to ignore of course. :)

  • Along these lines, the phrase "concepts from the last century" may be overstating things a bit


    Maybe this little summary helps: Which Sata Card? (especially the last paragraph, the 'one size fits it all' doesn't exist and that the 'right' implementation depends on the person dealing with the problem)?

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