Resizing a LUN on WIN2K8 Server

[MR_BRAXLOR]

Being new to he NetApp arena, I'm unsure of the methods to accomplish what would seem to be simple tasks. I was hoping to get some valid information from the community!

I am trying to resize a LUN on a WIN2K8 virtual in Hyper-V. When I look at SnapDrive on the local box to resize, the LUN is listed at max size. So I thought I could go to the System Manager and resize the LUN from there. After verifying the volume had enough space for the growth, I procedeed to resize the LUN. However, prior to making the change, the application asked for comfirmation and warned that I should first perform recommended steps on the host side. What are these steps? I could not find any NetApp documentation describing this process.

What recommended steps should I be performing?

[jalmanza]

Did SnapDrive give you any errors? Typically, when resizing a NTFS volume on a LUN we recommend using SnapDrive as it will use the native APIs from Microsoft to resize the partition and filesystem automatically.

When using FilerView or SystemManager to resize a LUN, all you have done is increase the container size (read: LUN) but not the important host-side tasks like resize the partition and filesystem. Remember, ONTAP cannot "see" inside the LUN, and since the host owns the partition and filesystem info within that LUN, you will need to extend those via the host in order to take advantage of the resize.

In Windows, typically you will run DISKPART to extend the partition and filesystem, I'm not sure if there is an additional steps for a HyperV CSV, which is why I typically recommend using SnapDrive.

[MR_BRAXLOR]

Thanks for the reply!

I couldn't see anything to do within SnapDrive. When I go to resize the drive from there, it tshows me it is already at it's max size. The only place I could find to expand it further was threough the System Manager. I could tell form other posts that diskpart was used to extend partitions on WIN2K3, but I didn't know if WIN2K8 was smart enough now to expand onthe fly through the Manager.

Is there another location in SnapDrive where I should be looking to increase the max size of the disk? Or do I disconnect the drive, expand it through System Manager, run diskpart on the WIN2K8 virtual, then connect the drive again?

[jalmanza]

If everything is set up correctly, then SnapDrive should give you a 'slider' bar in the resize disk window. Which is why I'm wondering if you got any errors. I'd check the Application event log for something like "Access Denied" or "RPC Server Unavailable" from SnapDrive.

[MR_BRAXLOR]

I've got the slider bar. However, the slider is all the way to the right, and I can't add anymore space cause I'm at the max size of the current LUN. I need to be able to increase the size so I can 'slide the bar' more to the right. I have plenty of available space on the volume.

[radek_kubka]

My two cents:

Is the box ticked or un-ticked next to "reserve space for at least one snapshot copy"?

What is the space gurantee and fractional reserve set to on the volume in question? (to find out: vol status yourvolname -v)

Regards,

Radek

[MR_BRAXLOR]

The box is ticked. The guarantee is 'volume' and fractional reserve = 0.

[radek_kubka · Accepted solution]

Un-tick the box in question - if it's ticked, SnapDrive tries to keep 100% of the LUN size as a free space in the volume to satisfy fractional reserve (despite the fact FR is set to 0, not 100).

Regards,

Radek

[MR_BRAXLOR]

That did the trick! Once unchecked, I could allocate the remaining free space of the volume. Thanks for your help!

[aborzenkov]

You do realize that if you have any snapshot on this volume you are now in much more risk of LUN running out of space? If there are snapshots you should consider setting reasonable FR.

[radek_kubka]

If there are snapshots you should consider setting reasonable FR.

Thanks for opening a can of worms, Andrey!

Seriously though:

1) Good starting point to get one's head around the concept of FR:

http://communities.netapp.com/groups/chris-kranz-hardware-pro/blog/2009/03/05/fractional-reservation--lun-overwrite

(have a look at the TR-3483 doc Andrey mentioned somewhere else, http://www.netapp.com/us/library/technical-reports/tr-3483.html)

2) The 'official' best practice is to set FR to zero - with the number of caveats, like enabling vol autosize and/or snap autodelete

3) As usual, your mileage may vary and there is a number of threads on communities around this topic

Regards,

Radek

[aborzenkov]

Well, I mentioned it because of previous statement “could allocate the remaining free space of the volume”. This sounds far too dangerous for me to do without considering all implications.

[jalmanza]

The good news is that if SnapDrive created the LUN, the n the space reserved bit on that LUN should be on, that way, snapshots will fail as opposed to the LUN being taken off-line due to a full volume.

Assuming that the guarantee is set to volume (which is the default) then there should be nothing to worry about ... except for not having enough space to take snapshots

[aborzenkov]

LUN space reservation only cares about space in Active File System. If FR is set to 0, then nothing is additionally reserved when snapshot is created. So you can have 100G volume with 100G LUN completely full and still create snapshot. Any attempt to write to LUN fails at this point.

[MR_BRAXLOR]

Thanks for the exrta info! I overspoke when I said 'allocate the remaining free space'. I still have ~120GB free space on the volume and my snaps are taking up about 28GB. I will be setting them to autodelete, thought it seems like right now SnapDrive is doing them from the local box and not the System Manager. I will definately be reading over those documents on FR and make sure that they system was setup with best practice in mind.