Hello,
When you use a flavor with an ephemeral disk size different from zero, the instance is booted with an extra virtual disk whose size is indicated by the ephemeral value (in GB). Using cirros image, try a flavor with ephemeral disk size different from zero (you need to create one yourself because the "standard" flavors have ephemeral size equal to 0), then log into the just booted instance and type: *$ ls /dev/vd** /dev/vda /dev/vda1 /dev/vdb Disk /dev/vdb is a (virtual) disk, automatically created at boot time, corresponding to the ephemeral disk space indicated by the flavor . Please note that /dev/vda, mounted as /dev/vda1, is the boot disk, always created when you boot an instance. Verify the size of the available disks; more specifically, verify /dev/vdb: * * *$ sudo fdisk -l* Disk /dev/vda: 1073 MB, 1073741824 bytes 255 heads, 63 sectors/track, 130 cylinders, total 2097152 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Device Boot Start End Blocks Id System /dev/vda1 * 16065 2088449 1036192+ 83 Linux Disk /dev/vdb: 1073 MB, 1073741824 bytes 16 heads, 63 sectors/track, 2080 cylinders, total 2097152 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/vdb doesn't contain a valid partition table Please note that /dev/vdb is made available as raw device, meaning that you need to partition and format it before using. You can find instructions on how to do that here http://docs.openstack.org/folsom/openstack-compute/admin/content/configure-nova-volume.html(search for command fdisk) Also note that this disk, being ephemeral, disappears when you terminate the VM. If you want to keep the data you produce with a VM that is destined to be terminated, you need to use Volumes that you explicitly create and attach using the services implemented by Cinder (former nova-volume). For what concerns the size you define for the boot disk, try and lunch two instances: one with flavor m1.tiny the other with m1.small: -- tiny -- *$ sudo fdisk -l * Disk /dev/vda: 41 MB, 41126400 bytes 255 heads, 63 sectors/track, 5 cylinders, total 80325 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Device Boot Start End Blocks Id System /dev/vda1 * 16065 80324 32130 83 Linux -- small -- *$ sudo fdisk -l * Disk /dev/vda: 21.5 GB, 21474836480 bytes 255 heads, 63 sectors/track, 2610 cylinders, total 41943040 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Device Boot Start End Blocks Id System /dev/vda1 * 16065 41929649 20956792+ 83 Linux As you notice, the size indicated by the flavor has effects on the size of the boot disk. Hope it helps, Marco. On Mon, Dec 3, 2012 at 7:03 PM, Ahmed Al-Mehdi <ahmedalme...@gmail.com>wrote: > Hello, > > I instantiated a VM using the cirros image, using the pre-defined > "m1.small" (1 VCPU, 2 GB Ram, 20G boot disk, 0 Ephemeral disk). I then > logged into the console of the VM to view some system stats. The num of > CPU and memory makes sense, but I am a bit confused on the storage aspect. > I see the output of "df -h " as following: > > $ df -h > Filesystem Size Used Available Use% > Mounted on > /dev 1001.1M 0 1001.1M > 0% /dev > /dev/vda1 23.2M 12.9M 9.1M 59% > / > tmpfs 1004.1M 0 1004.1M > 0% /dev/shm > tmpfs 200.0K 20.0K 180.0K 10% > /run > > > What is the difference between Boot disk and Ephemeral disk? > > How can I correlate the 20G boot disk to the output of "df -h". > > > Regards, > Ahmed. > > > _______________________________________________ > Mailing list: https://launchpad.net/~openstack > Post to : openstack@lists.launchpad.net > Unsubscribe : https://launchpad.net/~openstack > More help : https://help.launchpad.net/ListHelp > >
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