Capacity Mgt of SAN Volumes

[anthony_baldini]

I could use some assistance in capacity management of volumes containing a LUN.

Example:

I have a 280GB FlexVol with a single LUN of 140GB. It currently has 87GB of data on it.

The volume Snapshot Reserve is set to 0 and the LUN has Fraction Reserve set at 100.

A df -rh reveals that the volume is using 259GB....there is only 2.9GB of snapshots.

How to I determine what is using all the space?

I have RTFM'd (Read the Fabulous Manual) the Block Mgt Guide; there is a great section that explains Fractional Reserve, etc-but I just not "getting it".

Perhaps there is something on NOW that explains this better than the Block Mgt Guide? Maybe Blocks for Dummies?

Thanks in advance.

Tony

Filesystem	total	used	availal	reserved	Mounted on
/vol/ST2_3/	280GB	259GB	20GB	116GB	/vol/ST2_3/
/vol/2_3/.snapshot	0MB	2911MB	0MB	0MB	/vol/ST2_3/.snapshot

[jooss]

> I have a 280GB FlexVol with a single LUN of 140GB. It
> currently has 87GB of data on it.The volume Snapshot Reserve
> is set to 0 and the LUN has Fraction Reserve set at 100.
>
> A df -rh reveals that the volume is using 259GB....there is
> only 2.9GB of snapshots. How to I determine what is using all
> the space?

The df -rh should show that ~116GB is reserved. The LUN is taking 140GB, the snapshots 2.9GB and the reserve is 116GB. My assumption is that the host fileystem is showing 87GB used but there is actually 116GB of data in the LUN and therefore the reserve is also 116GB. TR3483 goes into gory detail regarding this.


> I have RTFM'd (Read the Fabulous Manual) the Block Mgt Guide;
> there is a great section that explains Fractional Reserve,
> etc-but I just not "getting it".
>
> Perhaps there is something on NOW that explains this better
> than the Block Mgt Guide? Maybe Blocks for Dummies?

With 7.2.4 we are in the process of changing all our documentation to the standard recommend of setting fractional reserve = 0 and enabling autodelete (trigger = volume) to be sure that there is always space available. I refer to this as the "X + Delta" configuration. This is not only much more efficient it is infinitely easier to understand because the space consumed is equal to the LUN space (whatever size the LUN or LUNs are configured as) and the snapshot space:
Used Space = LUN(s) size + Snapshot space

Cheers,
Rick