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NetApp snapmirror bandwidth option

Posted on 2014-08-10
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Last Modified: 2014-08-14
EE,

Hi thanks in advance for the help.

My question is how should we throttle snapmirror within the /etc/snapmirror.conf file? (or wizard) when transferring 3TB of data to another filer over a 20GB fiber link? We have 20GB from the NetApp to the switch via two 10GB cables and two 10GB fibers over a single vPC from switch to switch connecting to the other storage over the same configuration. I know NetApp throttles but am not sure how the initial sync will affect the performance and bandwidth of the system

Thanks again everyone
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Question by:snyderkv
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LVL 124
ID: 40252032
Do you need to throttle the Snapmirror action, at a particular time?

We found we needed to throttle the bandwidth of a snapmirror function overnight when all our snapmirror functions occurred to our DR site, because we also carry VOIP telephone functions across to the DR site, when using the DR LAN, and it cause all the telephones to be lost.....

If you use a bandwidth throttle, your initial sync will take much longer to complete.

Are they any other vital network services that use this link you need to "protect" ?
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Author Comment

by:snyderkv
ID: 40252066
Oh you're saying your DR site is actively has VOIP services? Good point. Yes we do use it as a "warm" site if you will and have random services over there possibly VOIP but is avoided when need be.

So the question is, how much do you throttle and do you pick specific interfaces for the snapmirror traffic as well?
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LVL 124

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by:Andrew Hancock (VMware vExpert / EE MVE^2)
Andrew Hancock (VMware vExpert / EE MVE^2) earned 664 total points
ID: 40252073
We do not pick specific interfaces, we use our production VLAN to snap mirror over, the reason for this is because our WAN link to DR site at present does not support VLANs, and we have no control over QoS for the WAN link, so therefore we have to reduce the bandwidth which Snapmirror uses.....

This has been done by trial and error....

we now use

kbs=1024 to kbs=2000
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LVL 42

Assisted Solution

by:Paul Solovyovsky
Paul Solovyovsky earned 668 total points
ID: 40252192
If the system is not under load another option you may want to look into is snapmirror compression.  Typically we get 1:4 to 1:8 compression and really helps the initial seeding process as well as replication with limited bandwidth.
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Author Comment

by:snyderkv
ID: 40252463
You mean deduplication? We have turned that on as I understand replication is more efficiant. I won't know if the system or network is under load until initialization but 2 mbs over a 20GB link? I'll re read the netapp snapmirror document but I don't remember much talk about this
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Author Comment

by:snyderkv
ID: 40252757
Oh you mean network compression. We have 20GB link that is unsaturated with just a few services. I don't think it would make sense to enable compression.
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Author Comment

by:snyderkv
ID: 40252851
From what I read from doc tr-3446 is that the NetApp does not throttle and is unlimited. I'm not sure how it works but I think the 7MB windowing keeps it from saturdating the link. In any case we are going to leave the default. If anyone has better information than I gathered please provide.
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Accepted Solution

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robocat earned 668 total points
ID: 40252880
You are unlikely to saturate a 10Gbit link. Even unthrottled, we've never seen an initial transfer go above 2-3Gbit. This is probably due to limitations in the disk subsystems.

Should you run into any issues, you can still dynamically adjust the throtlle value of a running transfer with the cli command "snapmirror throttle".
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Author Comment

by:snyderkv
ID: 40253298
Ah I didn't think about that, the writes are limited by the 10k rpm disks whatever that comes out to
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Author Closing Comment

by:snyderkv
ID: 40260462
Ok it ran fine with defaults, no compression or throttling. Jumbo frames are enabled but I thought it was odd that we only get a couple hundred megs of throughput. I also noticed I can run multiple concurrent snapmirrors at the same exact time (5 Total) with no change in CPU or network according to sysstat -s before and after every snapmirror initialization.
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Author Comment

by:snyderkv
ID: 40260464
By no change I mean no change between 1 and 5 snapmirror initializations. It does increase from 0 to 1 and then stays.
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