Im very new in using ESXI/vSphere and im planning to create an FTP server and i just needed to know some few basic things.

How do i gradually increase the disk capacity in a virtualize environment or is it even possible?

a typical scenario would be, i initially utilize 10GB storage capacity for FTP server, and as demand increases, i can easily increase it to 20GB.

what type of filesystem do i need to achieve this? or do i have to create a virtualize harddisk?


Enlarging the disk in VMWare is the easy part, for that you go into the VM Settings and type in a larger number. (So long as you have space free on your data store, or your using thin provisioning and you are aware of the limitations of over provisioning.)

The bigger issue comes within the OS that your FTP server is running on. What operating system are you planning on running within VMWare?

If its linux server then you can use LVM which allows for on the fly disk expansion.

To do this you 1st enlarge the disk in VMWare then you create an additional disk in the new space, combine them into a single 'volumegroup' then extend the 'logicalvolume' then resize the file system. This can all be done while the system is live and running.


If the FTP daemon is running on a windows server then you want to have 2 partitions/disk and make sure that your FTP share is stored on the 2nd disk. Its not possible to expand the drive/partition marked as 'system' from the install of windows that is running on it.


I hope this makes sense.

  • 1
    I would not consider LVM a good approach to resizeable storage in Linux virtual machines. It complicates matters unnecessarily if what you want is actually resize the virtual disk and not just add another one to your LVM volume group for extension. – the-wabbit May 15 '13 at 7:43
  • True it can complicate matters but it does allow for on the fly expansion. In my experience you can expand a regular disk without using LVM but you will have to reboot the guest VM after expanding the disk in vmare for it to detect the new total size. This is not always possible with mission critical production servers. Depending on the role this server provides for the original poster this may not be possible. – Jon Totham May 15 '13 at 7:54
  • Even if the disk is unmounted / filesystem extended / remounted? – symcbean May 15 '13 at 9:03
  • @JonTotham It certainly is not necessary to reboot the host in order to rescan the LUN. Windows Disk Management even offers a GUI option in the context menu of the disk for this, with Linux, a simple echo 1 > /sys/block/sdX/device/rescan triggers the rescan with the result reported in the kernel log. I have expanded enough VMware disks on the fly without any downtime with different flavors of guest systems to be able to tell you for sure that it works and has significantly less implications than fiddling about with LVM. – the-wabbit May 15 '13 at 10:17

Virtual disks on ESXi are easily expanded - even online, without ever having to shut down the guest. But obviously, you would need to resize partitions and filesystem structures within the guest. Under Linux (I am assuming you are using Linux since Windows would not give you that much of a choice in terms of filesystems anyway), Ext-type filesystems can be resized without unmounting using ext2resize, XFS and BTRFS are grown rather easily too. Partitions however are more of a problem - you would need to unmount the filesystem for it to become effective (Linux would not re-read the partition table with filesystems off the disk still mounted). So if you want to minimize downtime because of resizes your options would be:

  1. do not use partitions but place your filesystem on the "raw" virtual disk. This has some manageability issues - most admins (and most disk-related tools) look for the partition table to get an idea of what's on the disk. If you do not use a partition table, the disk might be considered "empty" by mistake and its content get overwritten.
  2. do not resize at all - create a "thin provisioned" virtual disk which has plenty of space for future growth and place your FTP store there. This has two potential issues:
    • A thin-provisioned virtual disk obviously has additional overhead and an additional layer where fragmentation can occur (although the effect of both would be negligible in most scenarios)
    • if you have a use case where a lot of temporary data is created and deleted, the virtual disk might grow significantly larger than your actual filesystem's space needs are and you might have difficulties reclaiming this space from the datastore (a "storage migration" operation would help, a guest filesystem issuing TRIM commands for unused disk blocks would too when using ESXi 5.1 or newer as Hypervisor)
  3. use a NAS store layer (NFS or Samba) as your storage for FTP where you would be able to hide the resize operation from your FTP server

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