Longhorn question On harvester nodes do we add muitlple disk rancher-users #harvester

Title

proud-addition-21854

11/18/2022, 3:29 PM

Longhorn question. On harvester nodes, do we add muitlple disks by “Add Disk” or do we add a Raided single disk?

full-plastic-79795

11/21/2022, 2:23 AM

Both should work, but I'm not sure which is the best practice for longhorn. There are many things to consider: performance, security, and ease of operation and maintenance. I created an issue on github https://github.com/harvester/harvester/issues/3183 to track this and get advice from longhorn experts

proud-addition-21854

11/21/2022, 3:23 PM

Say if you have two 100GB disks on each node. They both mounts as seperate extra disks. Now when I upload an image 125GB, it fails saying “No space left”. How do we handle images larger than a size of a single disk?

full-plastic-79795

11/21/2022, 3:27 PM

In this case, it seem that the only option is to increase the size of the hard drive, either by using multiple hard drives for RAID or by using a larger single hard drive

proud-addition-21854

11/21/2022, 3:28 PM

Hmm ok. How about creating a virtual machine or a volume larger than 100GB? Have not tried yet but what is going to happen?

full-plastic-79795

11/21/2022, 3:31 PM

longhorn replica can't be scheduled because there are no disks have enough space

proud-addition-21854

11/21/2022, 3:41 PM

Say I have , 3 nodes. each with 2x 100GB disks

The VM i am creating is 125Gb in size

full-plastic-79795

11/21/2022, 3:47 PM

Oh, sorry. I forgot that longhorn storage can be overcommit, since the default storage overcommit setting is 200%. I guest it will success. https://docs.harvesterhci.io/v1.1/advanced/settings#overcommit-config

proud-addition-21854

11/21/2022, 3:50 PM

May be I am asking too much , but how about if you need a thick provisioned vm?

full-plastic-79795

11/21/2022, 3:53 PM

What do you mean

a thick provisioned vm

? the example vm with 125G disk?

proud-addition-21854

11/21/2022, 3:54 PM

RIght. I mean nonsparse or preallocated disk volume

full-plastic-79795

11/21/2022, 3:58 PM

Maybe I will use

qemu-img

to shrink vm image first

proud-addition-21854

11/21/2022, 4:02 PM

The image is a qemu-img converted image and it took down to 125GB from 275GB.

full-plastic-79795

11/21/2022, 4:05 PM

The vm is successfully created in favor of storage overcommit.

proud-addition-21854

11/21/2022, 4:06 PM

Thank you. I will test it when I can and report here

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