sinhome
Contributor
Contributor

thin provision on SSD backed datastore

hi all

no doubt, thin provisioning can help to increase the utilization when using HDD-backed datastore.

i have been thinking if thin-provisioning can also help for SSD

i mean since the out-place-updated is used in SSD, the usable physical space of a virtual disk will eventually (soon) reach its promised upper bound, right ?

will this make thin-provision less meaningful for SSD-backed datastore?

thanks Smiley Happy

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eddzta
Contributor
Contributor

Hi sinhome,

As far as I'm aware the out-of-place updating mechanisms don't affect the usable space as far as VMFS/NFS is concerned (I could be wrong).

What I would suggest is to follow the regular guidelines when it comes to thin vs thick provisioning, THIN if you want to over commit and efficiently use space, THICK if you are not concerned about space utilization and want to guarantee write space. From my understanding there are minimal performance differences between the two types, but when running High I/O Intensive workloads through the storage, the difference is hardly noticeable.

So I would say Thin provisioning is no less meaningful on SSD Storage and still provides all the benefits it would on a HDD backed Datastore!

sinhome
Contributor
Contributor

hello eddzta

thanks Smiley Happy

if hypervisor does not control the usable space (i.e., physical disk space) of a virtual storage (e.g., a VMDK), is that possible for a virtual storage to consume entire space of the SSD?

For example, a 20MB virtual storage could consume nearly all space of an 256GB SSD due to out-of-place update mechanism?

i thought there should be such a limitation on usable space of a virtual disk, but I haven't find any information that can support my point...  Orz

thanks again

looking forward any suggestions or opinions    : )

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JarryG
Expert
Expert

What your are talking about is completely out of OS-control. It is SSD-controller that takes care of this. So let controller do its job and use SSD in simiar way as any other datastore.

Just remember to keep enough free space on SSD so that controller could do garbage-collection and other cleaning stuff. I recommend total OP ~20%. When I went above 80% usage, performance started to degrade...

_____________________________________________ If you found my answer useful please do *not* mark it as "correct" or "helpful". It is hard to pretend being noob with all those points! 😉
sinhome
Contributor
Contributor

hi JarryG

thanks for the reply :smileylaugh:

I wonder if there is a need to set the limit on physical usable SSD space for a virtual disk in the future

(due to the fact that a write-intensive virtual storage could consume large amount of SSD space, leading to frequent GC which can be perceived by the other co-existing virtual storages)

thanks again  ^^

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