2012-03-20 02:27 AM
Last night all lun's of a specific volume went down due to a lack of space in the volume. (there was 500Mb left).
We don't use snapshots on volume or on the presented luns.
We thought that we could fill up the volume up to max (100% usage) but this seems to be a misunderstanding.
We extended the volume and now there is 255 gb free space available but Ontap stil gives a warning:
The volume is 94.62% full (using 3.97 TB of 4.20 TB).
Can anyone tell me if it is possible to fill up a volume up to its maximum with LUN's
so that you can use the max of the disc capacity ?
No snapshots are being made (ONTAP nor application snapshots)
Thanks in advance
2012-03-20 06:48 AM
I have several volumes that only have LUNs with no snapshots and are at or almost at 100%. Make sure that your LUNs are space reserved (in other words, NOT thin provisioned). Double check that you have no snapshots in the volume.
2012-03-20 07:07 AM
make sure the fractional reserve and snap reserve are set to 0 and it is good to go but not a best practice to reach 100%, always netapp recommended is 80% and max is 90%. If you are performing any NDMP backup's, obviously we will have issues. Moreover if the LUN capacity is used to 100%, the volume and LUN will go offline and we will serve data.
Please follow the best practices.
2012-03-20 07:08 AM
You have to be mindful of the fractional reserve when dealing with LUNs. If your volume has a "volume" guarantee, your fractional reserve is 100% by default and can be changed. If you volume guarantee is set to "file" the fractional reserve is 100% and cannot be changed. In a volume of 30G with a LUN of 10G, an extra 10G (100% fractional reserve) of space in the volume will be set for the LUN to guarantee writes.
If you run out of space in your LUN and go beyond your fractional reserve, your writes on the LUNs will stop and your app will go down. Set the volume size to 2*LUN_size + Extra_Storage space (could be snapshots space, could be extra storage for volume storage reporting...). If the size of your LUN has become inadequate for your environment, you may want to further expand the volume using the formula above then use snapdrive to expand the LUN.
2012-03-20 07:29 AM
Just an idea:
Rather than stretch ONTAP 'patience' & try whether filling up a volume will break things, why not use thin provisioning on a volume level (guarantee set to "none") & make the volume in question way bigger than the LUN? This way you are achieving your goal of not locking any 'white space' in the aggregate.
I can't find anything in writing, but some bells are ringing that there should be some free space left in a volume, regardless of snapshots, etc.
2012-03-21 07:14 PM
This was discussed in one of the thread: https://communities.netapp.com/thread/20260
I think you can. See here:
I created a volume of 60m:
[root@shoemaker-rhel6x64-01 ~]# ssh sin vol size volt
vol size: Flexible volume 'volt' has size 60m.
Set snap reserve to 0%
[root@shoemaker-rhel6x64-01 ~]# ssh sin snap reserve volt
Volume volt: current snapshot reserve is 0% or 0 k-bytes.
Tried to create a LUN of 60m with no reserve:
[root@shoemaker-rhel6x64-01 ~]# ssh sin lun create -s 60m -t windows -o noreserve /vol/volt/lunt
lun create: created a LUN of size: 62.8m (65802240)
Hope this is useful
2012-04-04 07:14 AM
Found out why the lun's went off line.
Yes you can fill a volume with lun's up to 100% but..... don't use deduplication then.
If you do you have to reserve a amount extra space (you loose a part of the benefits of deduplication)
2012-04-04 10:37 AM
I have found a useful trick to avoid having LUNs go offline but don't over-allocate space is to enable autogrow on the volume. This is done through the "vol autosize" command, and possibly via System Manager. The volume then can grow to accommodate the space it needs to function.