Contributor
Contributor

Thin vs Thick provisioning

Hello all

We are running VSphere and have been doing some testing migrating THICK to THIN provisioning.

Our storage areas have grown a lot larger than what is being used

Changing to THIN provisioning seems like a good fix, but there has to be a down side.

Can someone explain the disadvantages to using THIN vs THICK??

thanks in advance for your help

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14 Replies
Immortal
Immortal

Hello.

Can someone explain the disadvantages to using THIN vs THICK??

Need to be monitored closely (set up alarms) to ensure you don't run out of space.

Can't use VMware FT with them.

Sometimes they need "maintenance" to shrink them back down.

Surely there are others, but the possibility of running out of space is clearly the biggest disadvantage.

Good Luck!

Brian Atkinson | vExpert | VMTN Moderator | Author of "VCP5-DCV VMware Certified Professional-Data Center Virtualization on vSphere 5.5 Study Guide: VCP-550" | @vmroyale | http://vmroyale.com
Immortal
Immortal

Brian explained the main threat - watch free space closely.

Also a big number of thin provisioned VMs on slow storage can affect performance due to frequent metadata updates.


---

MCSA, MCTS, VCP, VMware vExpert '2009

http://blog.vadmin.ru

EMCCAe, MCITP: SA+VA, VCP 3/4/5, VMware vExpert http://blog.vadmin.ru
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Virtuoso
Virtuoso

Hello.

Can someone explain the disadvantages to using THIN vs THICK??

Need to be monitored closely (set up alarms) to ensure you don't run out of space.

What do you guys do once the "alarms" fire off? Buy more disks? Beg people to let you delete their VMs? Smiley Happy

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Immortal
Immortal

Buying more disk isn't usually an option for me :). I will usually SVMotion things around or clean up what I can. I'm a bit difficult on sizing requirements to begin with, so I tend to do more disk growing along the way vs chasing them from this end.

Brian Atkinson | vExpert | VMTN Moderator | Author of "VCP5-DCV VMware Certified Professional-Data Center Virtualization on vSphere 5.5 Study Guide: VCP-550" | @vmroyale | http://vmroyale.com
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Immortal
Immortal

Performance is also a small consideration, there is a little overhead for thin provisioned files, they could take a hit as they grow.

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Virtuoso
Virtuoso

Vmware posted a short paper on Thin Provisioning performance on vSphere you check out for that part.

http://www.vmware.com/pdf/vsp_4_thinprov_perf.pdf






www.phdvirtual.com, makers of esXpress

www.thevirtualheadline.com www.liquidwarelabs.com
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Contributor
Contributor

I appreciate all that gave a suggestion on "Thin vs Thick"

We will be starting with our test servers and see how that goes.

We monitior with alarms and email...I'm hoping this doesn't turn into a constant tweaking of the VM's

thanks to all that offered suggestions

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Virtuoso
Virtuoso

Good luck with everything in your environment andyour testing.






www.phdvirtual.com, makers of esXpress

www.thevirtualheadline.com www.liquidwarelabs.com
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Expert
Expert

There can be also an issue that thinly

provisioned LUNs come from a pool of common storage, it is possible for

multiple LUNs to overlap the same disk or disks, and this could create

performance problems as applications compete for drive access.

---

iSCSI SAN software

http://www.starwindsoftware.com

--- iSCSI SAN software http://www.starwindsoftware.com
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Enthusiast
Enthusiast

I am wondering what you mean by 'maintenance'... How is this done?  Can I 'reclaim' freed space?

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Immortal
Immortal

Hello.

Check out Duncan Epping's blog entry "Storage VMotion and moving to a Thin Provisioned disk" for more information.

Good Luck!

Brian Atkinson | vExpert | VMTN Moderator | Author of "VCP5-DCV VMware Certified Professional-Data Center Virtualization on vSphere 5.5 Study Guide: VCP-550" | @vmroyale | http://vmroyale.com
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Enthusiast
Enthusiast

Thanks, I was under the impression that some kind of script/tool was available to 'reclaim' free space.

My understanding is: Vmware clears what the Os is setting free...

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Enthusiast
Enthusiast

Forget any maintenance or mojo to prevent VMs frome taking place... monitoring the free space is the only answer.

When you give more than you have be ready to go to the bank... meaning buying more disks will probably be necessary.

VMware doesn't by itself free deleted files from a vmdk... the mojo goes there (svmotion).

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Enthusiast
Enthusiast

If Thanks all for your answers.  I was not looking for any magic... I am well aware of the possible problems I can encounter with thin provisioning.

I want to know everything there's to know about thin provisionning before I move my VMs to thin.

Our situation is: a LOT (400+) of developpers machines were created with thick provisionning in ESX 3.5x.  These machines are now running on a 10-15 ESX 4.0 farm (Dell Quad-Quadcores).  After looking more closely, we came to the conclusion that many of these (all deployed from the same template) are using 40-50% of their available space.  Since this is a 'developpers farm', machines are changing (created and deleted) a lot, using thin provisionning will give us some slack (instead of buying more disks...)  Space is not really an issue for us, but wasted space IS...

I've seen that the thin performances impacts are negligible compared to thick... so I will have a new Storage defined and will 'storage vmotion' all of them, from thick to thin.

If I'm overlooking something, please tell me.

BTW: a quick one... should I 'upgrade' all my VM to version 7, since I still have more than 300 that are not?

If yes... What's the gain?

Or.. Should I start a new topic???

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