[openstack-dev] [cinder] Can I use lvm thin provisioning in mitaka?

Marco Marino marino.mrc at gmail.com
Sat Jan 21 09:00:42 UTC 2017


Really thank you!! It's difficult for me find help on cinder and I think
this is the right place!
@Duncan, if my goal is to speeding up bootable volume creation, I can avoid
to use thin provisioning. I can use image cache and in this way the
"retrieve from glance" and the "qemu-img convert to RAW" parts will be
skipped. Is this correct? And whit this method I don't have a performancy
penalty mentioned by Chris.
@Chris: Yes, I'm using volume_clear option and volume deletion is very fast

Marco



2017-01-20 18:24 GMT+01:00 Duncan Thomas <duncan.thomas at gmail.com>:

> There's also cinder functionality called the 'generic image cache' that
> does this for you; see the (per-backend) config options:
> image_volume_cache_enabled, image_volume_cache_max_size_gb and
> image_volume_cache_max_count
>
> On 20 January 2017 at 16:54, Chris Friesen <chris.friesen at windriver.com>
> wrote:
>
>> On 01/20/2017 04:07 AM, Marco Marino wrote:
>>
>>> Hi, I'm trying to use cinder with lvm thin provisioning. It works well
>>> and I'd
>>> like to know if there is some reason lvm thin should be avoided in mitaka
>>> release. I'm trying to use with
>>> max_over_subscription_ratio = 1.0
>>> so I don't have problems with over subscription.
>>> I using thin provisioning because it is fast (I think). More precisely,
>>> my use
>>> case is:
>>>
>>> - create one bootable volume. This is a long operation because cinder
>>> download
>>> the image from glance, qemu-img convert in raw format and then "dd" copy
>>> the
>>> image in the volume.
>>> - Create a snapshot of the bootable volume. Really fast and reliable
>>> because the
>>> original volume is not used by any vm.
>>> - Create a new volume from the snapshot. This is faster than create a new
>>> bootable volume.
>>>
>>> Is this use correct? Can I deploy in the production environment (mitaka
>>> - centos 7)
>>> Thank you
>>>
>>
>> For what it's worth we're using cinder with LVM thin provisioning in
>> production with no overprovisioning.
>>
>> What you're proposing should work, you're basically caching the vanilla
>> image as a cinder snapshot.
>>
>> If you wish to speed up volume deletion, you can set "volume_clear=none"
>> in the cinder.conf file.
>>
>> Be aware that LVM thin provisioning will see a performance penalty the
>> first time you write to a given disk block in a volume, because it needs to
>> allocate a new block, zero it out, then write the new data to it.
>>
>> Chris
>>
>>
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>
>
>
> --
> --
> Duncan Thomas
>
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