Linux Archive

Linux Archive (http://www.linux-archive.org/)
-   Device-mapper Development (http://www.linux-archive.org/device-mapper-development/)
-   -   dm-thinp: new device mapper target to thin provision storage (http://www.linux-archive.org/device-mapper-development/433008-dm-thinp-new-device-mapper-target-thin-provision-storage.html)

Phillip Susi 09-28-2010 09:44 PM

dm-thinp: new device mapper target to thin provision storage
 
On 9/28/2010 4:49 PM, Heinz Mauelshagen wrote:
>
> These are 2 new device mapper targets "thinp" and "thinp-dev"
> implemented in one module, which allow for thin provisioning of storage
> on a single host from a storage pool to an arbitrary amount of devices.

How is this different than snapshotting a zero target?

> +Create an ext4 filesystem on the thin provisioned device:
> +mkfs -t ext4 /dev/mapper/thinp1

FYI, that tends to spend a lot of time writing hundreds of mb of zeros
to the inode tables, allocating chunks from the backing store. You
might want to add -E lazy_itable_init to stop that.

--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel

Hannes Reinecke 09-29-2010 06:29 AM

dm-thinp: new device mapper target to thin provision storage
 
Phillip Susi wrote:
> On 9/28/2010 4:49 PM, Heinz Mauelshagen wrote:
>> These are 2 new device mapper targets "thinp" and "thinp-dev"
>> implemented in one module, which allow for thin provisioning of storage
>> on a single host from a storage pool to an arbitrary amount of devices.
>
> How is this different than snapshotting a zero target?
>
Main difference is that you actually can free up space.
You can't with snapshotting as then a rollback
becomes impossible.

Cheers,

Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@suse.de +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Markus Rex, HRB 16746 (AG Nürnberg)

--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel

Heinz Mauelshagen 09-29-2010 11:25 AM

dm-thinp: new device mapper target to thin provision storage
 
On Tue, 2010-09-28 at 17:44 -0400, Phillip Susi wrote:
> On 9/28/2010 4:49 PM, Heinz Mauelshagen wrote:
> >
> > These are 2 new device mapper targets "thinp" and "thinp-dev"
> > implemented in one module, which allow for thin provisioning of storage
> > on a single host from a storage pool to an arbitrary amount of devices.
>
> How is this different than snapshotting a zero target?

Like Hanness mentioned: you can free space.

>
> > +Create an ext4 filesystem on the thin provisioned device:
> > +mkfs -t ext4 /dev/mapper/thinp1
>
> FYI, that tends to spend a lot of time writing hundreds of mb of zeros
> to the inode tables, allocating chunks from the backing store. You
> might want to add -E lazy_itable_init to stop that.

Thanks for the hint, I waned to have load on the thin provisioned
devices so far for testing but will have a look at the reduced
allocations with this option.

>
> --
> dm-devel mailing list
> dm-devel@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel


--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel

Heinz Mauelshagen 09-29-2010 11:25 AM

dm-thinp: new device mapper target to thin provision storage
 
On Wed, 2010-09-29 at 08:29 +0200, Hannes Reinecke wrote:
> Phillip Susi wrote:
> > On 9/28/2010 4:49 PM, Heinz Mauelshagen wrote:
> >> These are 2 new device mapper targets "thinp" and "thinp-dev"
> >> implemented in one module, which allow for thin provisioning of storage
> >> on a single host from a storage pool to an arbitrary amount of devices.
> >
> > How is this different than snapshotting a zero target?
> >
> Main difference is that you actually can free up space.
> You can't with snapshotting as then a rollback
> becomes impossible.
>

Yes, that's right.

Heinz

> Cheers,
>
> Hannes


--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel

Phillip Susi 09-29-2010 01:41 PM

dm-thinp: new device mapper target to thin provision storage
 
On 9/29/2010 7:25 AM, Heinz Mauelshagen wrote:
> On Tue, 2010-09-28 at 17:44 -0400, Phillip Susi wrote:
>> How is this different than snapshotting a zero target?
>
> Like Hanness mentioned: you can free space.

Could you clarify that a bit? Is space only freed if you reduce the
length of a device? You can't do the same with a snapshot?

--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel

Heinz Mauelshagen 09-29-2010 03:20 PM

dm-thinp: new device mapper target to thin provision storage
 
On Wed, 2010-09-29 at 09:41 -0400, Phillip Susi wrote:
> On 9/29/2010 7:25 AM, Heinz Mauelshagen wrote:
> > On Tue, 2010-09-28 at 17:44 -0400, Phillip Susi wrote:
> >> How is this different than snapshotting a zero target?
> >
> > Like Hanness mentioned: you can free space.
>
> Could you clarify that a bit? Is space only freed if you reduce the
> length of a device? You can't do the same with a snapshot?

Not just when you shrink a device, you can release all allocations to an
inactive thin provisioned device as well.

With snapshots the exception store is dropped when you delete the
snapshot as well.

But you can't drop allocated space of a partial exception store because
the exception size is much smaller than the allocation units lvm2 goes
by (ie. extents sized 128MB). Thus dropping exceptions related to a now
past EOD segment within the origin just gives you stale exceptions in
the table w/o the option to reduce allocated space.

>
> --
> dm-devel mailing list
> dm-devel@redhat.com
> https://www.redhat.com/mailman/listinfo/dm-devel


--
dm-devel mailing list
dm-devel@redhat.com
https://www.redhat.com/mailman/listinfo/dm-devel


All times are GMT. The time now is 01:27 AM.

VBulletin, Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Relevant URLs by vBSEO ©2007, Crawlability, Inc.