how to vertically expand a ReadyNAS 104

If you are going to expand the volume and take advantage of RAID redundancy protection, then the additional drive needs to be at least as large as the two you have.  If it is larger, the additional space above that of the current drives will not be utilized.  You would need to add a 4th or replace one of the existing with a larger one to use that space, so it has a place for the redundancy to reside.

If you want to use the additional drive as a separate, non-redundant volume, then it can be any size.  But you'll have to disable XRAID before you insert it.

I think I was pretty clear on what happens.  What your options are, and how these things are sold can be misleading.    As I said, you just about have to be an IT expert.  What is that?

"An information technology (IT) specialist is a computer support and security administrator who assists companies and organizations with managing hardware, software, networking and solving problems. These professionals go by a range of titles, including information security analyst and network administrator."

YOU as just a normal person are somehow expected to know about a NAS, or a Wifi Router, and all these other things that used to be in the domain of the IT expert.   So it's not your fault for not really understanding.  Or sure about what you're buying and how to use it correctly.   I'm always learning new things in this area and so it's easier for me, but trying to keep up with it all when I'm not an IT expert.  I get by thanks to the Internet these days to learn what I need to.  

So you can buy a NAS which is just short for "Network Attached Storage"  Really, it's just a computer with a number of HDD's that you talk to remotely.  You normally don't have a Monitor, Keyboard, and Mouse Attached to one.    Most run a custom version of LINUX as the ReadyNAS does, which is Linux Debian 9 currently I believe.   You really don't need to worry about that.   You get a nice Interface when you log into your NAS,  kind of like looking at Windows instead of a CLI (Command Line Interface).  You can click your way around instead of having to type in commands. 

Now you can buy a NAS in a number of sizes.  How many discs it can hold.  Normally, cheaper HOME NAS units are 2 or 4 bay.  I normally say, just get the 4 bay unit as it's generally not all that much more money.  If you don't use all 4 bays right away, that's just fine.  You can also get NAS with even more.  I have a ReadyNAS 516 which has 6 bays.  But you can get 8 or 12, or even larger.  I think they can get up to like 48 HDD in one unit.  Generally, 6 or more bays start getting into Business Class NAS units.  Prices go up to match. 

Normally, when you get a NAS, it's for the RAID Capabilities, otherwise, you would just buy an External HDD, plug it into your USB port on your computer and be done with it.  In fact, many Wifi Routers have USB ports on them, where you can, in fact, plug a USB HDD into that and use it as a Network drive.  My ASUS Router has that capability.  I've never done it as I have a NAS.    Now if that 1 HDD fails, as all HDD's will fail at some point.  Maybe 1 month, maybe 1 year, maybe 10 years.  You just never know.  This is why you backup your Data.  You need at least 2 if not more copies of your Data, and offsite is even better.  If your House burns down, or you get robbed, or whatever, do you want to lose that Data?   So I have 2 NAS Units.  1 is used to back up my MAIN NAS.  When you have 13+ TB of Data, the only practical way to back that up is with another NAS.  You want your Laptop or Desktop Backed up.  My Pictures and Text files and some other things I have backed up off-site using Carbonite.   If you have a Smartphone, backing up all your pictures to Google, or Apple, or Amazon, etc, some for free. 

When you use your NAS as 2 HDD's combined into a single Partition,  This is normally called RAID 0.  It splits data evenly across two or more disks, without parity information, redundancy, or fault tolerance. Since RAID 0 provides no fault tolerance or redundancy, the failure of one drive will cause the entire array to fail; as a result of having data striped across all disks, the failure will result in total data loss!!!   

That is what you were expecting to happen, and advertised in a way.  Pop in that second HDD and double your space!!!   Except for not knowing the results of doing that.  Since 1 HDD can fail at any time.  Now you throw a second HDD into the mix, your odds of a failure of losing everything goes up!!!  If one HDD fails you lose your Data on BOTH HDD's. 

This is why I say the Ad's are misleading.  They sell these 2 bay NAS units and say,  sure it can hold 20TB of Data.  Of course, it can if YOUR DUMB!!!!!  You can pop in 2 10TB HDD into the thing, use RAID 0 and get almost 20TB of space.  But if 1 HDD fails, you just lost 20TB of Data if your NAS is filled up that much.  Now if you had 2 of them, and backed up 1 to the other, it would be OK!!!  You would have Redundancy doing that.  Now I do use RAID 0 on my Second NAS.  Because it's only a cheap 4 Bay NAS, and I use 2 8TB HDD in it.  This gives me enough space to back up my 13TB on my other NAS.   But see, it's a BACKUP!!!  That means 2 copies.    If I lose Data on either, I have a backup on the other NAS.  Also, that cheap NAS of mine is only on 2 days a week late at night.  That is when my Main NAS backs up to it.  The rest of the time it's powered off.  So 95% of the time it's not running.   It's all Automatic.  I don't have to really do anything but check and make sure all is good once in a while.  Sometimes update the OS on the backup NAS as it can get behind as I don't normally look at it.  It's normally only on 12:30PM to about 6AM for 2 days a week.

What any normal NAS will do, be it a 2 or 4 bay or larger, if you have just 1 HDD, it's just like a normal single External HDD you plug into your computer.  Once you pop a second HDD into the NAS is where the magic starts to happen.  It'll copy the Data on the first HDD to the new Second HDD.  This is called RAID 1.  Now you have a CLONE of the original HDD.  This is giving you 2 copies.  A single location, but it's at least a Backup.  If either HDD fails, you don't lose any data.  Just pop in a new HDD where the old one was, and the Data from the old good drive gets copied to the new drive.  You're back once again to 2 copies of your Data and you didn't lose anything.

Now you can disable XRAID, and set the NAS to use each HDD on its own.  So that it's like having 2 external HDD plugged into your computer.  Each can be set up to have its own mapped drive letter.    This allows you to use the 3TB of space on each drive like you were expecting to, just not as 1 large volume.   So they're each on their own.   The Benefit of this is you do get full storage of each drive.  If 1 HDD fails, you only lose Data on that 1 HDD.  The other still works for however long its life is.    But again it's kind of a waste of a NAS.  You get a NAS in general for RAID and some safety.

With a 2 Bay NAS, you just don't have the flexibility you do with at least a 4 bay NAS.  See with 2 Bay NAS, the real only redundancy you have is RAID 1.  It's nice to have.  But if you get a 3TB HDD, it's a 3TB NAS.  That's because it's using RAID 1.   I know when you pop that second HDD you spent money on you expected more space.  What you were really doing was creating a Backup of sorts.  That's a good thing.  You're not getting more space, but you are getting an Automatic CLONE of your Data.   But you're stuck at that point with a 2 bay NAS.  That's fine for some people.  There is Vertical Expansion though.  So you could have popped in a 6TB drive into it.  Let it rebuild, you won't see that extra space until after it's rebuilt, and you pop in a second 6TB HDD.  Now you've doubled your space and still have RAID 1 redundancy.    Yes, it's spending yet more money!!!  That's one way to go if you only have a 2 bay NAS and want more space without buying a new NAS!!!  

Now if you had a 4 bay NAS, you would have 2 slots free.  Once you popped that second HDD in, you have RAID 1 and redundancy.  A Backup.  That is how you should look at it.  Having a Backup is a good thing.  But you have 2 extra spaces.  So you can now buy a 3rd HDD and pop that in.  Now you not only have Redundancy,  but your space can now expand.  It will on it's own change to RAID 5.  Now if any of the 3 HDD's fails, You still have your Data, pull out the BAD HDD, and pop in a new HDD of equal or larger size.  If it's larger than the other 2, you won't get any extra space.  You would need at least 2 larger HDD's to gain more space.   So you stick with just 3 HDD's.  You've doubled your storage space now and you have some redundancy.  You can call it HDD Magic.  It's amazing that the Data on any of the HDD's that fails can be rebuilt onto a new HDD and not lose anything.  To me that's Amazing.    But when you get close to using up most of the space with 3 drives, you can then just pop in a 4th HDD.  It stays RAID 5.  You still gain more space, and still, have a 1 HDD redundancy.  If any of the 4 HDD fail, you won't lose any of your Data.  Pull the bad HDD and replace with a new HDD, and the other 3 HDD will rebuild the Data onto your new HDD.  This is why I recommend a 4 bay over a little cheaper 2 bay unit.   To me, a 2-bay NAS is silly.

When you start getting into larger NAS Units, in the 7, 8 bay and larger, then you can get into RAID 6.  This is like RAID 5, but allows 2 HDD's to fail at once and still be able to rebuild your Data without losing anything.  But you basically lose 2 HDD's worth of Data storage instead of 1 HDD like with RAID 5. 

So I don't recommend 2 bay NAS units.   Spend a few dollars more and get the 4 bay version.  The HDD's are going to end up costing more than the NAS unit.   But if you don't need to fill it up with HDD's, then don't.  I never did.  I started with 2 and grew to 4 over time.  Then Replaced that NAS with my 516 which is 6 bays.  I added a 5th HDD and later a 6th HDD.  I'm about full, so I'll have to start vertical expanding myself.  I have 6 3TB HDD's currently.

But a RAID, especially anything more than RAID 1, is not a real BACK UP.  If one HDD fails, you can swap out and be up and running in no time and not lose anything.  BUT again, maybe the NAS takes a dump. Maybe you get robbed.  maybe your place burns down.  Bye, bye Data!!!   

Windows computers use a file format on HDD called NTFS.   You may have also heard of FAT and FAT32.   Apple just changed over on iOS and MacOS to their new AppleFS last year.  The Linux OS uses EXT3 or EXT4 and some others.  One of those that the ReadyNAS units use these days is called BTRFS.  Which is a file system based on the copy-on-write (COW) principle, initially designed at Oracle Corporation for use in Linux.  As far as I know, there are no real Windows Drivers to access this format.   There are some experimental Windows drivers.

All the drives in the NAS, in general, should be the SAME SIZE!!!!  You can't add a smaller HDD. It has to be Equal or Greater.  So say you pop in 4 3TB HDD into your NAS.  That's just fine.  Or 4 8TB HDD's into your NAS.  Whatever.  That is what you want to do.  Now say you have 4 3TB HDD in your NAS and it's about full.  What do you do?  Well one thing you can do, and it's called Vertical Expansion as I said above,    As you go from 2, to 3, to 4, etc, that's Horizontal Expansion.    So you maxed out your 4 bay NAS doing that.   You need more space.  Now you can do Vertical Expansion.   You can pull out the HDD's,  1 at a time, and say go from a 3TB HDD to a 6 TB HDD.  In effect, changing all 4 HDD doubles your storage space.  NOW, this is the important part, you ONLY do 1 HDD, and then the NAS has to rebuild to that new HDD you just popped in.  That can take HOURS depending on what size of a HDD you are using.    You have to let the NAS rebuild.  If you just start pulling out all your HDD, you're going to lose your Data.  So only 1 HDD, let it rebuild, and then you can repeat.  

Now you will gain NO extra storage space using just 1 larger HDD.    Think about it.  Say you have 3, 3TB HDD in and 1 6TB HDD in and the 6TB fails.  A 3TB HDD can't hold 6TB's of Data.  So how could you expect the NAS to rebuild all the Data on a larger HDD?  It can't.  So the NAS would treat the 6TB HDD as a 3TB HDD. That's ok.  When you pop in a 2nd 6TB HDD, the NAS will rebuild once again, and then you'll gain more room.   When that's done, move to the 3rd, rebuild, and then the 4th, rebuild.  You'll have the max space if all are the same size.

Some people around here don't understand this because they are not an IT expert, and so they pull 1 HDD,  pop in larger and right away, do another and then another, lose all their Data and now don't understand where all their Data went?   Because they didn't let the NAS copy the Data to the New HDD one at a time.  This could be a 4 day process to swap out 4 drives in a NAS!!!! 

No matter what you do, I think you'll end up spending money unless you don't care about redundancy.   I don't know what you want out of your NAS?   If you really don't care about the Data on the NAS, take the gamble, use RAID 0.  

I have a TIVO, if you know what that is, a DVR that records TV programs.  Well, you can plug in an External drive to gain more space.  The problem with that is basically the same thing.  if either HDD fails you lose all that Data.  In this case, all the TV shows you've recorded.   So it's not something people recommend.  Instead do what I did, pulled out the 500Gig drive that it came with and popped in a single 3TB HDD.  I greatly expanded the space without doubling my HDD failure odds.  3TB is the largest you can go with just popping in a new larger HDD.  If you go larger, there are a few tricks you need to do plugging the drive into your computer first.    3TB in my TIVO is a ton of space!!!    It's your Data and your Risks and it's on you what you want to do.   

Lastly, when I'm spending my money on something, I try to get as much Data as I can on it.  Learn as much as I can to see if it fits my needs and does what I expect it to do.  I just don't go blindly buying anything.  I'm not spontaneous!!!  Which is why I give you Links on things like RAID.  So you can read and learn and understand a little more.  What you learn can help you, your friends and family if they're looking into this stuff. Maybe not fall into the same kind of trap you may have.    Know the Pro's and Con's.     

https://en.wikipedia.org/wiki/Standard_RAID_levels

https://en.wikipedia.org/wiki/Network-attached_storage