David,

Keep in mind that snapshots will only grow if you delete files. So if your data incorporates a lot of deletes, then you need to take that into consideration.

If this is a database, you will want to quiesce the DB to snapshot it; if the data is simple text files, you can snap it on the fly using the volume snap schedules. Giacomo mentioned setting your snap sched to 0 0 0, but if you're not using Snapmanager or other 3rd party backups and this is not a database, you'll want to allow snapshots to take place on a schedule.

From: David.Ashton@rullion.co.uk [mailto:David.Ashton@rullion.co.uk]
Sent: Thursday, September 04, 2008 9:33 AM
To: Milazzo Giacomo
Cc: Willeke, Jochen; owner-toasters@mathworks.com; toasters@mathworks.com
Subject: Re: R: Noob...

thanks all for the excellent advice and pointers. I'll remove the snap reserve, I think the sizing is probably correct then.

The lun is mounted on a windows server that has snapdrive installed. The rate of change - varies from 3GB somedays to 80GB on others.
The server runs a legacy app that uses an enormous 3.6 million flat text files (220GB), and the number of open files is in the 10,000's at any one time so it gets a battering.

Dave

Rullion Management Services Ltd is a company registered in England and Wales with company number 2797732.

"Milazzo Giacomo" <G.Milazzo@sinergy.it>
Sent by: owner-toasters@mathworks.com

04/09/2008 14:06

To	"Willeke, Jochen" <Jochen.Willeke@wincor-nixdorf.com>, <David.Ashton@rullion.co.uk>, <toasters@mathworks.com>
cc
Subject	R: Noob...

A first answer came from Jochen and I’ve to add that if you have a volume that has to contain a LUN (that is, with NetApp, a file) the default snapshot reservation area of 20% (or less) must be removed, so the snap schedule.
In your case

Filer> snap reserve vol_bond 0
Filer> snap sched vol_bond 0 0 0

This in case you use some software of Snapmanager suite (You did not tell us the usage of that lun) or the snapmirror snapshots will be placed in the active file system area having the necessary free space. Never size a volume less that 2/2.5 time the size of the contained luns.

Bye

Da: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] Per conto di Willeke, Jochen
Inviato: giovedì 4 settembre 2008 12.54
A: David.Ashton@rullion.co.uk; toasters@mathworks.com
Oggetto: RE: Noob...

Hi David,

as far as i can see, everything is as expected.
When you have fractional_reserve set to 100 (%), as soon as you create snapshots on that volume, ontap will reserve 100% of the Luns size within the volume, to gurantee writes to complete successfully.

The maths show:

820GB * 0,8 (for snap reserve) = 656 GB

320GB Lun * 2 (for fractional reserve) = 640 GB

P = 640 / (656*100) = 97,56 %

Think ontap is doing some rounding, so 98% is correct.

Regards

Jochen

From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of David.Ashton@rullion.co.uk
Sent: Thursday, September 04, 2008 12:04 PM
To: toasters@mathworks.com
Subject: Noob...

Hi, please excuse my noobness, I've recently inherited a Netapp system or 3, I'm fairly new to SANs in general and netapp in particular. This isnt my full time gig (storage), its one thing amongst the 2 thousand other things I'm working on today, but I allocate a fair amount of time to figuring this stuff out.

I'm struggling with something I'm sure all netapp storage people go through, I've read the manuals, I've played around for about 6 months on the filers and I cant answer this.

I have a FAS3020. I have a volume, lets call it vol_bond. Its 820GB, 20% snap reserve. It contains one lun, which is 320GB. The space guarantee is volume, and fractional reserve is 100.

Currently, there are 5 snapshots, totalling 8GB. It is snap mirrored to another filer. Snapshots are created nightly, there are no problems with that. At weekends, after various backup activity, these grow to about 80GB, but we only keep 5 and they're deleted.

Its all up and running, everythings fine.

Except for the filer status which reports: /vol/vol_bond is full (using or reserving 98% of space and 0% of inodes, using 49% of reserve) and the df -r output is

/vol/vol_bondv8/ 687865856 670681368 17184488 335194536 /vol/vol_bondv8/
/vol/vol_bondv8/.snapshot 171966464 14140040 157826424 0 /vol/vol_bondv8/.snapshot

What am I missing? I thought I had this thing nailed but obviously not.

Dave Ashton

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