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From: Donal Lafferty <donal.lafferty@citrix.com>
To: Mike Tutkowski <mike.tutkowski@solidfire.com>, "dev@cloudstack.apache.org"
	<dev@cloudstack.apache.org>
Subject: RE: Disk Allocated Versus Disk Used
Thread-Topic: Disk Allocated Versus Disk Used
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Date: Thu, 15 Aug 2013 09:33:00 +0000
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Hi Mike,

I've had problems with GUI stats as well.  I tried to solve the issue by fo=
cusing on the kernel commands that are used to populate database entries th=
e GUI relies on.

There seem to be three important commands:  GetStorageStatsCommand, Startup=
StorageCommand and ModifyStoragePoolCommand.  GetStorageStatsCommand is cal=
led on a regular basis, StartupStorageCommand is returned by a Hypervisor a=
gent once when it connects to the management  server, and  ModifyStoragePoo=
lCommand  is called once when primary storage is configured.  The commands =
have fields for capacity, used, and available.

Problems were that I found the term 'capacity' ambiguous, and that ModifySt=
roagePoolCommand seemed to take a different view on what 'availableBytes' m=
eans.

For, 'capacity',  I went with an implementation that set 'capacity' to tota=
l storage device volume and 'available' to unallocated space.  E.g.

public static void GetCapacityForLocalPath(string localStoragePath, out lon=
g capacityBytes, out long availableBytes)
{
...
    System.IO.DriveInfo poolInfo =3D new System.IO.DriveInfo(fullPath);
    capacityBytes =3D poolInfo.TotalSize;
    availableBytes =3D poolInfo.AvailableFreeSpace;
...

'used' became the difference between the two, e.g. for GetStorageStatsComma=
nd

object ansContent =3D new
{
    result =3D result,
    details =3D details,
    capacity =3D capacity,
    used =3D capacity - available
};
return ReturnCloudStackTypedJArray(ansContent, CloudStackTypes.GetStorageSt=
atsAnswer);

StartupStorageCommand does not have a 'used'.  Instead it returns "availabl=
e" and "capacity", e.g.

StoragePoolInfo pi =3D new StoragePoolInfo(
                        poolGuid.ToString(),
                        ipAddr,
                        localStoragePath,
                        localStoragePath,
                        StoragePoolType.Filesystem.ToString(),
                        capacity,
                        available);

However, I have a note on the ModifyStoragePoolCommand to double check the =
meaning of available.  E.g.

var poolInfo =3D new
{
    uuid =3D uuid,
    host =3D cmd.pool.host,
    localPath =3D cmd.pool.host,
    hostPath =3D cmd.localPath,
    poolType =3D cmd.pool.type,
    capacityBytes =3D capacityBytes,
    // TODO:  double check whether you need 'available' or 'used' bytes?
    availableBytes =3D availableBytes
};

What has your experience been with ModifyStoragePoolCommand?


Finally, if the agent reconnects with a different identifier, you end up tw=
o entries in the database.  One for the previous connect and one for the ne=
w connection.  This messes up your storage stats.


DL


From: Mike Tutkowski [mailto:mike.tutkowski@solidfire.com]
Sent: 14 August 2013 23:05
To: dev@cloudstack.apache.org
Cc: Donal Lafferty
Subject: Re: Disk Allocated Versus Disk Used

I wonder if Donal can answer this question?

On Fri, Jul 12, 2013 at 7:18 PM, Mike Tutkowski <mike.tutkowski@solidfire.c=
om<mailto:mike.tutkowski@solidfire.com>> wrote:
In looking at my Xen boxes, disksizeused appears to equate to used space.

disksizeallocated, I presume, should equate to what Xen calls allocated spa=
ce, but it does not seem to (ex. the GUI wasn't showing anything, but in Xe=
nCenter it says 8 GB allocated space for one of my hosts).

On Fri, Jul 12, 2013 at 7:13 PM, Mike Tutkowski <mike.tutkowski@solidfire.c=
om<mailto:mike.tutkowski@solidfire.com>> wrote:
Hi,

I noticed in the 4.2 GUI under the details of Primary Storage that the Disk=
 Allocated field always seems to be empty.

I changed the logic to display the disksizeused field (instead of the disks=
izeallocated field) and now it seems to work.

Can someone tell me what the difference is supposed to be between these two=
 fields and if the change I made should be checked in (along with changing =
the name of this field from Disk Allocated to Disk Used)?

Thanks!

--
Mike Tutkowski
Senior CloudStack Developer, SolidFire Inc.
e: mike.tutkowski@solidfire.com<mailto:mike.tutkowski@solidfire.com>
o: 303.746.7302<tel:303.746.7302>
Advancing the way the world uses the cloud<http://solidfire.com/solution/ov=
erview/?video=3Dplay>(tm)


--
Mike Tutkowski
Senior CloudStack Developer, SolidFire Inc.
e: mike.tutkowski@solidfire.com<mailto:mike.tutkowski@solidfire.com>
o: 303.746.7302<tel:303.746.7302>
Advancing the way the world uses the cloud<http://solidfire.com/solution/ov=
erview/?video=3Dplay>(tm)


--
Mike Tutkowski
Senior CloudStack Developer, SolidFire Inc.
e: mike.tutkowski@solidfire.com<mailto:mike.tutkowski@solidfire.com>
o: 303.746.7302
Advancing the way the world uses the cloud<http://solidfire.com/solution/ov=
erview/?video=3Dplay>(tm)

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