2010-02-16 04:33 AM
Hi there, I've recently starting looking at our environment and trying to see why our dedupe levels for CIFS and NFS were so low.
On our NFS volume for VM's we were getting about a 27% saving - I've used sdelete to 'zero' out a lot of white space ineach of the VM's and I'm now up to 67% - so much happier. I still have a few misaligned VM's (P2Vs) which I'll be turning my attention to, so hopeuflly I can improve on this figure even more.
However where I'm struggling is my CIFS volume. I appreicate the value I get "depends" on a lot of factors. However I'm getting about 23% so my question is this - what values are others getting?
I've nothing really to base my "I think it should be higher" than a couple of passing comments I've had from conusltants.
What can I start to look at?
Just as a bit more information on the volume:
Total size is 360Gb
used data: 141.5Gb
Available data: 128.5Gb
Available snapshot: 62.6Gb
Used snapshot: 27.4Gb
Snap retention is: keep last 6 hourly and last 15 nightly snaps.
Make up CIFS volume is: Shared file area and user profiles.
73Gb - Office files
54Gb - Graphic files
12Gb - Mail files
10Gb - Text files
9Gb - Database files
4Gb - Video files
3Gb - Audio files
Any help or advice would be greatly appreciated.
2010-02-16 07:36 PM
Hi, on average we see around 30%-35% savings on user files with dedupe. What you are seeing might be as good as it gets, but if you are taking hourly snaps - this might also be the cause of the lower rate. Refer to TR-3505 in the netapp.com library - its our dedupe bible. What the TR says, in a nutshell, is if you take a snap and then dedupe, no duplicate blocks will be freed until that snapshot expires, and if you continue snapping every hour before dedupe can finish - you'll never get out this cycle. So here's something to try. If you can, try to give dedupe an extra hour to complete by skipping one snap each night, say, you 1am snap - i.e. schedule sis start to run after your midnight snap then resume your hourly snaps at 2am. Skipping one hourly snap might be all you need. After 15 days (once all your old snaps roll off) check your dedupe savings again and let us know if they went up. BTW I am pretty sure you can also run sis stat and it will tell you how long it took to run dedupe on the CIFS vol, this could also help identify if the snaps are colliding with the sis operation.
Hope that helps,
2010-02-17 02:37 AM
Thanks to you both for your replies, good to know what others are getting savings-wise!
And Dr Dedupe, TR-3505 is now downloaded and I'll have a good read - cheers for the suggestion, Our nightly snap occurs at midnight and takes between 23 and 40 seconds depending on the rate of change, the dedupe on this volume also starts at midnight and takes around 6-7 minutes (System Manager is useful!! ) so I'll change the timing of this, see what happens and report back once the snaps roll off the back of my schedule.