Hi Marco, This is really good stuff, thank you very much for helping out. I am creating some instances to test out how/where the different storage related elements are created.
I created two VM instance: Instance 1 : 20GB boot disk Instance 2 : 10GB boot disk, 2 GB Ephemeral disk. root@bodega:/var/lib/nova# ls -lh -R instances instances: total 12K drwxrwxr-x 2 nova nova 4.0K Dec 4 09:01 _base drwxrwxr-x 2 nova nova 4.0K Nov 28 11:44 instance-00000001 drwxrwxr-x 2 nova nova 4.0K Dec 4 09:01 instance-00000002 instances/_base: total 240M -rw-r--r-- 1 nova nova 40M Dec 4 08:51 8af61c9e86557f7244c6e5a2c45e1177c336bd1f -rw-r--r-- 1 libvirt-qemu kvm 10G Dec 4 09:01 8af61c9e86557f7244c6e5a2c45e1177c336bd1f_10 -rw-r--r-- 1 nova kvm 20G Dec 4 08:51 8af61c9e86557f7244c6e5a2c45e1177c336bd1f_20 -rw-rw-r-- 1 nova nova 9.4M Nov 28 11:44 8af61c9e86557f7244c6e5a2c45e1177c336bd1f.part -rw-r--r-- 1 nova nova 2.0G Dec 4 09:01 ephemeral_0_2_None <====== -rw-r--r-- 1 libvirt-qemu kvm 2.0G Dec 4 09:01 ephemeral_0_2_None_2 <===== instances/instance-00000001: total 1.9M -rw-rw---- 1 nova kvm 26K Nov 28 11:45 console.log -rw-r--r-- 1 libvirt-qemu kvm 1.9M Dec 4 07:01 disk -rw-rw-r-- 1 nova nova 1.4K Nov 28 11:44 libvirt.xml instances/instance-00000002: total 1.8M -rw-rw---- 1 libvirt-qemu kvm 27K Dec 4 09:02 console.log -rw-r--r-- 1 libvirt-qemu kvm 1.6M Dec 4 09:03 disk -rw-r--r-- 1 libvirt-qemu kvm 193K Dec 4 09:01 disk.local -rw-rw-r-- 1 nova nova 1.6K Dec 4 09:01 libvirt.xml root@bodega:/var/lib/nova# It seems all the boot disk and ephemeral disk are created as files in /var/lib/nova/instance/_base. I don't understand why there are two files of size 2GB (lines marked above with <=====). I will look into that later on. I am running into an issue creating a volume for which I will post a separate message. Thank you again very much. Regards, Ahmed. On Tue, Dec 4, 2012 at 8:56 AM, Marco CONSONNI <[email protected]> wrote: > Sorry, the directory you need to check is /var/lib/nova/instances. > > MCo. > > > On Tue, Dec 4, 2012 at 5:54 PM, Marco CONSONNI <[email protected]> wrote: > >> Hi Ahmed, >> >> very technical questions. >> I'm not sure my answers are right: I'm just an user... >> >> In order to answer, I've just look at what happens and made some guess. >> Feel free to verify yourself. >> >> I'm assuming you are using KVM as I'm doing. >> >> The space for the boot disk and the ephemeral disk should be represented >> as files in the physical node where the VM is hosted. >> In order to check that, go to directory /var/lib/nova on the node where >> the VM is running. >> As far as I understand, this is where nova (and KVM) keep the running >> instances' information. >> You should see a directory for each running instance named as >> instance-xxxxxxx, where xxxxxxx uniquely identifies an instance (there are >> several ways for uniquely identify an instance, this is one of many... but >> this is a different story). >> Go into one of these and check what you find. >> >> For what concerns nova-scheduler, I don't know what exactly does. I'm >> afraid that you need to test and see what happens. >> >> A nova command can help for inspecting what a node is using, in terms of >> resources. >> >> At the controller node (or any other node where you installed nova >> client), type the following command substituting OpenStack02 with the name >> of the node you want to inspect: >> >> *$ nova host-describe OpenStack02* >> >> >> +-------------+----------------------------------+-----+-----------+---------+ >> >> | HOST | PROJECT | cpu | memory_mb | >> disk_gb | >> >> >> +-------------+----------------------------------+-----+-----------+---------+ >> >> | OpenStack02 | (total) | 16 | 24101 | 90 >> | >> >> | OpenStack02 | (used_max) | 13 | 7680 | 0 >> | >> >> | OpenStack02 | (used_now) | 13 | 8192 | 0 >> | >> >> | OpenStack02 | 456ec9d355ae4feebe48a2e79e703225 | 4 | 2048 | 0 >> | >> >> | OpenStack02 | fb434e07b687494bb669fde23f497970 | 9 | 5632 | 0 >> | >> >> >> +-------------+----------------------------------+-----+-----------+---------+ >> >> It return a brief report of the resources currently used by a node. >> >> To my knowledge, the dashboard does not provide a similar page, at the >> time being. >> >> Hope it helps, >> Marco. >> >> >> >> >> On Tue, Dec 4, 2012 at 4:40 PM, Ahmed Al-Mehdi <[email protected]>wrote: >> >>> Hi Marco, >>> >>> Thank you very much for the info, much much clearer. I was looking for >>> the boot disk using "ls -l /dev/sd*", but the existence of /dev/vda1 >>> should have given me a clue. >>> >>> A few follow up questions: >>> >>> - I am assuming the space for the VM boot disk is allocated from the >>> local hard disk of the physical host on which the VM is instantiated, >>> right? >>> - If Yes >>> - How is the boot disk represented on the physical host. Is it a >>> file on the local filesystem that represent the VM boot disk? >>> - I am guessing there is some logic in nova-scheduler that checs >>> first if there is enough disk apace on the physical host for the VM(along >>> with RAM, >>> VCPUs) before launching the VM on the host? >>> - Is there any way to find out from Horizon how much disk space is >>> available on a (or each) physical host for VM boot disk allocation? >>> >>> Thank you, >>> Ahmed. >>> >>> >>> >>> >>> On Tue, Dec 4, 2012 at 12:07 AM, Marco CONSONNI <[email protected]>wrote: >>> >>>> 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 >>>> <[email protected]>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 : [email protected] >>>>> Unsubscribe : https://launchpad.net/~openstack >>>>> More help : https://help.launchpad.net/ListHelp >>>>> >>>>> >>>> >>> >> >
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