We have encountered high Disk IO on our Ubuntu 14.04 VM's running mongoDB. On Windows Azure.
To solve this issue we have changed the VM size from A2 to A3 (to add the additional data discs) and attached 4 additional VHD and set them as raid10 which works fine.
We now wish to detach the original data VHD (to minimize the VM size back to A2), but we encountered a new problem.
After detaching the original data VHD and restarting the machine we weren't able to connect to the VM through SSH, after attaching back the VHD everything returned to work normally.
Furthermore, if I'm detaching the VHD without restarting the machine, the machine is running normally, I can explore the mounted directories except that I can't see the VHDs (I see only the os disk and the temporary data disk). I've attached the relevant output of "lshw -c disk" command. (The original VHD which we want to detach is /dev/sdc)
Before
> *-disk
> description: SCSI Disk
> physical id: 0.0.0
> bus info: scsi@2:0.0.0
> logical name: /dev/sda
> size: 29GiB (31GB)
> capabilities: partitioned partitioned:dos
> configuration: sectorsize=512 signature=0004656b *-disk
> description: SCSI Disk
> physical id: 0.1.0
> bus info: scsi@3:0.1.0
> logical name: /dev/sdb
> size: 285GiB (306GB)
> capabilities: partitioned partitioned:dos
> configuration: sectorsize=512 signature=dae5f753 *-disk:0
> description: SCSI Disk
> physical id: 0.0.0
> bus info: scsi@5:0.0.0
> logical name: /dev/sdc
> size: 1023GiB (1098GB)
> capabilities: partitioned partitioned:dos
> configuration: sectorsize=512 signature=b9ecd70d *-disk:1
> description: SCSI Disk
> physical id: 0.0.3
> bus info: scsi@5:0.0.3
> logical name: /dev/sdd
> size: 256GiB (274GB)
> capabilities: partitioned partitioned:dos
> configuration: sectorsize=512 signature=c1832ca1 *-disk:2
> description: SCSI Disk
> physical id: 0.0.4
> bus info: scsi@5:0.0.4
> logical name: /dev/sde
> size: 256GiB (274GB)
> capabilities: partitioned partitioned:dos
> configuration: sectorsize=512 signature=334f6e39 *-disk:3
> description: SCSI Disk
> physical id: 0.0.5
> bus info: scsi@5:0.0.5
> logical name: /dev/sdf
> size: 256GiB (274GB)
> capabilities: partitioned partitioned:dos
> configuration: sectorsize=512 signature=32f22a65 *-disk:4
> description: SCSI Disk
> physical id: 0.0.6
> bus info: scsi@5:0.0.6
> logical name: /dev/sdg
> size: 256GiB (274GB)
> capabilities: partitioned partitioned:dos
> configuration: sectorsize=512 signature=bc60ee52
>
After
> *-disk
> description: SCSI Disk
> physical id: 0.0.0
> bus info: scsi@2:0.0.0
> logical name: /dev/sda
> size: 29GiB (31GB)
> capabilities: partitioned partitioned:dos
> configuration: sectorsize=512 signature=0004656b *-disk
> description: SCSI Disk
> physical id: 0.1.0
> bus info: scsi@3:0.1.0
> logical name: /dev/sdb
> size: 285GiB (306GB)
> capabilities: partitioned partitioned:dos
> configuration: sectorsize=512 signature=dae5f753
Thank you very much for your help,
