RB750Gr3 and the Micro SD card

Many MikroTik Routerboards are equipped with a micro SD card reader. This card reader is a great solution to expand the Routerboard’s internal storage. It’s also very interesting that many Routerboards will write data significantly faster on this card than on their own internal storage.

RB750Gr3 (a.k.a. Hex) is a small and affordable 5-port router with the built-in USB support, a micro SD card reader and even a hardware IPsec encryption chip. And even better, it can be a Dude server, too.

I purchased one unit to build my own Dude server. However, if you check the specifications, you will see that this model has only 16MB of internal disk (flash) space. Not enough space for the Dude’s database, even for the small one.

I checked the database size of my productional Dude and only the DB file is almost 44MB. In addition, we need more space for the support files, like MIBs, Dude system logs, device icons, etc.

 

Adding a micro SD card to my router

I purchased a few 16GB Class A1 micro SD card. Those cards have a very fast chips and their sustained write speed can be around 10MB/s, with the read speed of up to 100MB/s. I will not suggest here any specific manufacturer or model, however you should buy only a quality cards.

I inserted this card into the slot on my router and booted it. After my router turned on, I accessed it using the WinBox GUI.

Bear in mind that we can always work either from the command line or WinBox. I will show you both methods and you choose one that fits your needs.

In the WinBox GUI, navigate to System > Disks. That will open a new window with the list of all external disks currently attached to the router. This list will include all micro SD cards and USB pen drives.

RouterOS will not read the disk label of the FAT32 formatted disk, even if you assigned one. But don’t worry, we don’t need it here.

RouterOS is based on Linux. The native Linux file system is ext3. Therefore, we should format our micro SD card in this format. It’s not mandatory, but highly recommended.

If you just click on the disk and try to format it now, RouterOS will refuse the action with the error message that disk is in use. You need to Eject disk and then you can Format disk.

This process is really fast. In my case, it took about 35 seconds. When the formatting process completed, RouterOS will again enable this disk and show it in the list.

Even better, you will also see this new disk as the new folder in Files:

This means that you can access its content with the full name started with diskX/, where X is the ordinal number of the disk. In this example, my disk is disk1 and the full path will be disk1/myfile.

I already mentioned that you can also see any attached USB drive. I attached one in the same time and both disks appeared in the list.

 

Using the command line

The alternative way is to use the command line. In essence, this whole process is the same.

Here’s my example, intentionally left with all errors. For your convenience, I made all commands in bold.

[admin@MikroTik] > disk print
 # NAME            LABEL            TYPE    DISK                  FREE       SIZE
 0 disk2           NO NAME          fat32   SD                 14.6GiB    14.6GiB
[admin@MikroTik] > disk format-drive disk2 file-system=ext3 label=microSD
failure: disk is being used, eject it first
[admin@MikroTik] > disk eject-drive disk2                                
[admin@MikroTik] > disk print                                            
 # NAME            LABEL            TYPE    DISK                  FREE       SIZE
 0                                  unknown SD                            14.7GiB
[admin@MikroTik] > disk format-drive disk2 file-system=ext3 label=microSD
no such item
[admin@MikroTik] > disk format-drive 0 file-system=ext3 label=microSD     
  formatted: 100%

[admin@MikroTik] > disk print                                            
 # NAME            LABEL            TYPE    DISK                  FREE       SIZE
 0 disk1           microSD          ext3    SD                 14.6GiB    14.7GiB
[admin@MikroTik] > disk print
 # NAME            LABEL            TYPE    DISK                  FREE       SIZE
 0 disk1           microSD          ext3    SD                 14.6GiB    14.7GiB
 1 disk3           NO NAME          fat32   DataTraveler...     7.2GiB     7.2GiB
[admin@MikroTik] >

We can now use this new disk for any purpose, like a SMB share, the Dude DB or even system logs storage. This disk will be treated as the integral part of your router.

Stay tuned.