When to resize an instance
Resizing an infrastructure container running SmartOS or Container Native Linux offers the ability to scale vertically by resizing the configuration of a running container, without having to shutdown or reboot.
Resizing is the ability to increase or decrease the configuration of an infrastructure container running SmartOS, bhyve (Hardware Virtualized), or Container Native Linux, including disk size, cpu cap, and memory size. Currently, KVM (Hardware Virtualized) instances cannot be resized. For more information, see resizing KVM.
Bhyve (Hardware Virtualized) instances must use the flexible disk space feature (or be resized to a package that uses the flexible disk space feature) before they will allow resizing. Changes to memory or CPU in a bhyve instance will require a restart.
Please see managing instances for detailed instructions on how to resize.
As capacity requirements change, considerations for growth and/or scaling back an infrastructure become important business decisions. Additionally, resizing an infrastructure container running SmartOS or Container Native Linux can offer an immediate solution to unforeseen resource exhaustion.
As business needs or requirements change, the configuration requirements of an infrastructure container may also need changing. For example, you can increase the size of your instance to scale for growth without provisioning a new one.
If an instance runs out of disk space, resizing to a larger package will be necessary.
If you are able to SSH in to the instance, you can check the disk space using the df(1m) command (example output below):
container# df -h Filesystem Size Used Avail Use% Mounted on zones/4985f9fb-e674-e472-ac02-86e15242d6f7 26G 448M 25G 2% / /lib 263M 237M 27M 91% /lib /lib/svc/manifest 2.7T 673K 2.7T 1% /lib/svc/manifest /lib/svc/manifest/site 26G 448M 25G 2% /lib/svc/manifest/site /sbin 263M 237M 27M 91% /sbin /usr 417M 379M 39M 91% /usr /usr/ccs 26G 448M 25G 2% /usr/ccs /usr/local 26G 448M 25G 2% /usr/local swap 256M 28M 229M 11% /etc/svc/volatile /usr/lib/libc/libc_hwcap1.so.1 417M 379M 39M 91% /lib/libc.so.1 swap 128M 8.0K 128M 1% /tmp swap 256M 28M 229M 11% /var/run
In general, the critical filesystem to look at is
/ (root). If you see it reaching towards 100%, you'll want to either start cleaning up the filesystem, or resize the instance to a larger package size.
In some cases, you may not be able to ssh into the instance to due to a 100% full filesystem. You can often verify this by running the zfs(1m) command from the compute node where the instance lives:
computenode# zfs list zones/4985f9fb-e674-e472-ac02-86e15242d6f7 === Output from 44454c4c-3700-1039-8034-c2c04f445131 (78-2b-cb-0a-75-23): NAME USED AVAIL REFER MOUNTPOINT zones/4985f9fb-e674-e472-ac02-86e15242d6f7 21.6M 25.0G 448M /zones/4985f9fb-e674-e472-ac02-86e15242d6f7
If the AVAIL column shows 0, the instance has run out of disk space and will need to be resized in order to regain access.
Whether the instance runs out of memory or swap space, the instance is likely to become inaccessible (and services may start failing).
If you attempt to ssh into an instance that is suffering from memory exhaustion, you'll often see a message relating to
Resource temporarily unavailable. A reboot of the instance may temporarily resolve the problem, but will require some detective work to determine the underlying cause. In many cases, the solution is to resize the instance to a larger package size, thus allowing programs to run with more than enough memory.
You can check the memory of a instance from its compute node by running zonememstat(1m):
computenode# zonememstat -z 4985f9fb-e674-e472-ac02-86e15242d6f7 === Output from 44454c4c-3700-1039-8034-c2c04f445131 (78-2b-cb-0a-75-23): ZONE RSS(MB) CAP(MB) NOVER POUT(MB) 4985f9fb-e674-e472-ac02-86e15242d6f7 28 128 0 0
If you see the RSS column reaching it's CAP, and you're also seeing stats under NOVER (provides the number of times the instance has gone over its cap) and POUT (total amount of memory paged out when the zone has gone over its cap), the instance is likely suffering from memory exhaustion. Again, it's important to understand why the instance is running out of memory before concluding that a resize is the best solution.
Please also see analyzing zone memory utilization for more information on monitoring memory usage.
Some considerations that must be taken into account prior to resizing an instance include:
- Current disk used vs target disk size. If the amount of disk that is being used is greater than the target disk size, the resize will fail.
- While resizing can be done without the requirement of a reboot or shutdown, resizing does not auto-tune applications running an instance. You may have to tune your application to accommodate for the new configuration size, which may require a restart of services to take into effect.
- Ensure that the compute node has enough space to allow for your instance to be resized, if resizing to a larger size.
Resizing is not supported for KVM Hardware Virtualized instances. In place of resizing a KVM instance, you can provision a new instance on a new package, and then migrate the data from the original to new instance.
- To learn more about when to resize instances, including adding additional disks, see When to resize an instance.
- To learn more about sizing packages for your application, see Sizing guidelines.
- For information on how to use flexible disk space with bhyve, SmartOS, or Docker instances, see Configuring packages.