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Portal:Cloud VPS/Admin/VM flavors

From Wikitech

Each VM created with Openstack Nova is assigned a flavor. Flavor determines the following characteristics for a VM:

  • Number of vcpus
  • Available RAM
  • Available disk space for local storage
  • Storage backend (ceph or non-ceph)
  • Disk access rate limits
  • Scheduling hints that associated flavors with particular host aggregates

A flavor can be private or public. Public flavors are available for use by all projects; private flavors are assigned for limited use by one or more specified project. A private flavor cannot be made public, nor a public flavor made private.

Deprecating a flavor

When a flavor is deleted, VMs no longer display with their cpu/ram/disk usage in Horizon; rather they appear with an unavailable flavor. For that reason it's best to avoid deleting flavors as long as any VMS still exist using that flavor.

To prevent new VMs from being created with a flavor, don't delete them; disable them. Disabling is only vaguely supported in the nova apis, but setting the flag in the DB will make the flavor disappear from most Horizon UIs while still providing size info on the instance details page. 

root@cloudcontrol1003:~# mysql -u root nova_api_eqiad1
mysql:root@localhost [nova_api_eqiad1]> update flavors set disabled=1 where flavorid='<flavorid>';

General flavor guidelines

Flavor names begin with a generation count (e.g. 'g2' for 2nd generation flavors), followed by cores, ram, disk space. For example, a second generation flavor with 2 cores, 8 gigs of ram and 20Gb of disk space would be g2.cores2.ram8.disk20.

Each flavor must specify a scheduling pool (via aggregate_instance_extra_specs). An icinga alert will fire if a flavor is found without aggregate_instance_extra_specs.

Each ceph-enabled flavor must specify disk access rate limits. An icinga alert will fire if a flavor is found WITH aggregate_instance_extra_specs:ceph='true' but WITHOUT quota:disk_read_iops_secm quota:disk_total_bytes_sec, or quota:disk_write_iops_sec.

Public flavors should not be created with any quota above the following: 8 cores, 16G RAM, 160G disk. Users may request instances with larger specs, but these should be private flavors, created on an as-needed basis and associated only with specific, approved projects.

For private flavors, you should append the name of the project to the flavor (ex. g2.cores8.ram16.disk1120.wikidumpparse).

Example of flavor creation command for a private flavor using the cookbook (takes care of the naming, and the extra properties): 

dcaro@vulcanus$ wmcs.openstack.add_flavor \
    --cluster-name eqiad1 \
    --project wikidumpparse \
    --ram-gb 16 \
    --vcpus 8 \
    --disk-gb 1120

Equivalent through command line: 

user@cloudcontrol1005:~$ sudo wmcs-openstack flavor create \
    --ram 16384 \
    --vcpus 8 \
    --project wikidumpparse \
    --disk 1120 \
    --private \
    --property "aggregate_instance_extra_specs:ceph=true" \
    --property "quota:disk_read_iops_sec=5000" \
    --property "quota:disk_total_bytes_sec=200000000" \
    --property "quota:disk_write_iops_sec=500" \
    g3.cores8.ram16.disk1120.wikidumpparse

3rd generation flavors

Generation 3 flavors were created in March of 2021 to encourage use of Ceph. Generation 2 flavors had a variable root disk size and used LVM to partition space above 20Gb; in generation 3 nearly all flavors have a root disk of 20Gb, and LVM is not used; the root partition is automatically resized to fill available space.

Note that the lvm change is not technically tied to the flavor; the flavors were renamed at the same time that lvm was removed from the firstboot script.

Flavors that do NOT use Ceph should still be tagged with '.local-storage.' For example, a Generation 2 flavor used for a database host might be named g2.cores16.ram64.disk3000.local-storage. Local storage flavors should be quite unusual, and typically reserved for WMCS staff use and/or custom hardware.

Custom flavors also support swap and ephemeral partitions; these are only used in rare, project-local cases.

Some example of g3 flavors are: 

g3.cores1.ram2.disk20
g3.cores8.ram36.disk20
g3.cores4.ram8.disk20.swap24.ephem20
g3.cores8.ram16.disk20.ephem140

2nd generation flavors

Generation 2 flavors were created in September of 2020 to support the move to Ceph. Each g2 flavor is presumed to schedule in the standard Ceph pool 'eqiad1-compute'.

Flavors that do NOT use Ceph should be tagged with '.local-storage.' For example, a Generation 2 flavor used for a database host might be named g2.cores16.ram64.disk3000.local-storage. Local storage flavors should be quite unusual, and typically reserved for WMCS staff use and/or custom hardware.

Some example of g2 flavors are: 

g2.cores8.ram18.disk160
g2.cores4.ram8.disk80
g2.cores2.ram4.disk40
g2.cores1.ram2.disk20

1st generation flavors

Generation 1 flavors are legacy flavors that predate any attempt at standardization. Some use amazon-style 'm1' naming, some have usage-specific names. In addition, many have non-standard single-digit internal IDs rather than standard uuids.

Most of these flavors will be removed as soon as possible. Here is the complete list of 1st generation flavors as of September, 2020: 

2: m1.small
3: m1.medium
4: m1.large
5: m1.xlarge
7: m1.gigantic
21e9047d-a60f-499d-b7f5-51f83ddf3611: bigdisk2
c39bc0a6-71a2-4512-926e-43cccf5f8b4c: mediumdb
e48a8d9d-e735-4742-981f-b55f293d4115: bigram
e7261773-a931-4a72-b725-3ccf71580b18: largedb
72116845-7941-4d3d-9eb1-11084b7b1927: cloudvirt-canary
bd542f73-4fdb-4aa0-98dd-049406152392: cloudvirt-canary-ceph
62a89635-8a60-40d7-9b58-56594a071b0a: justdisk
2d59cc0d-538c-4bbd-b975-8e696a4f7207: c1.m2.s80
8af1f1cc-d95f-4380-bf10-bcfa0321b10f: c8.m8.s60
4cf440b0-b4c7-42b5-a18e-7746b50390fc: dumps-temporary-file-storage
101: ci1.medium
3a6d6aa8-05de-4811-b882-72595a4d6529: mediumram-ceph
7b92dec5-e831-4eef-abc8-1ed585c59c66: mediumram
cc0f1723-38d7-42da-aa2c-cef28d5f4250: xlarge-xtradisk
857921a5-f0af-4069-8ad1-8f5ea86c8ba2: m1.small-ceph
6606e793-2949-4beb-9051-50341fcafbf7: m1.xlarge-ceph
e4c6fb0b-0cf7-4f50-9f1f-db3eea00fb2c: m1.large-ceph
7b7df879-9750-4516-8e84-1de9896963f0: transferpy-test
65de37ea-f087-48d7-9769-0cd741a7219b: wdqs.full
f34a542a-a933-4341-8f43-ff8442f48a01: t206636
15675a68-8f3d-450b-af4b-d661a486c926: parsingtest
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