Behind the Scenes: Episode 128 – OnCommand Unified Manager 7.3

Welcome to the Episode 128, part of the continuing series called “Behind the Scenes of the NetApp Tech ONTAP Podcast.”

tot-gopher

This week on the podcast, Yossi Weihs (https://www.linkedin.com/in/yossiw/) and Philip Bachman (@pgbachman) join us to talk about the latest OnCommand Unified Manager release and make a compelling case around why everyone should be installing it.

If you’re interested in learning about OCUM 7.2, check out the previous podcast found here:

Behind the Scenes: Episode 83 – OnCommand Unified Manager 7.2

Finding the Podcast

The podcast is all finished and up for listening. You can find it on iTunes or SoundCloud or by going to techontappodcast.com.

This week’s episode is here:

Also, if you don’t like using iTunes or SoundCloud, we just added the podcast to Stitcher.

http://www.stitcher.com/podcast/tech-ontap-podcast?refid=stpr

I also recently got asked how to leverage RSS for the podcast. You can do that here:

http://feeds.soundcloud.com/users/soundcloud:users:164421460/sounds.rss

Our YouTube channel (episodes uploaded sporadically) is here:

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Removal of IP Fastpath in ONTAP 9.2

ONTAP 9.3 is already GA as of December, but there was a pretty significant change to how networking operates in ONTAP 9.2. However, this change impacts any release after 9.1, so it’s good to bring up.

I never really touched on it before, because we hadn’t seen any issues with it. However, we’re now seeing occasional problems resulting from that change, so I want to detail it all here.

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ONTAP 9.2 has modernized its networking stack to take advantage of new features and capabilities introduced by FreeBSD. As a result, one of the networking features that ONTAP used went away. This was known as “IP Fastpath.” (This also resulted in the removal of routing groups.)

What is IP Fastpath?

From the product docs:
https://library.netapp.com/ecmdocs/ECMP1368834/html/GUID-8276014A-16EB-4902-9EDC-868C5292381B.html

IP Fast path is an alternative routing mechanism to the routing table. In fast path, the responses to incoming network traffic are sent back by using the same interface as the incoming traffic. By avoiding the routing table lookup, fast path provides a quick access to data.

If fast path is enabled on an interface group and a physical interface in that group receives an incoming request, the same physical interface might not send a response to the request. Instead, any other physical interface in an interface group can send the response.

How fast path works with NFS/UDP

NFS/UDP traffic uses fast path only when sending a reply to a request. The reply packet is sent out on the same network interface that received the request packet.For example, a storage system named toaster uses the toaster-e1 interface to send reply packets in response to NFS/UDP requests received on the toaster-e1 interface.Fast path is used only in NFS/UDP. However, fast path is not used in other UDP-based NFS services such as portmapper, mountd, and nlm.

How fast path works with TCP

In a TCP connection, fast path is disabled on the third retransmission and the consecutive retransmissions of the same data packet. If Data ONTAP initiates a connection, Data ONTAP can use fast path on every TCP packet transmitted, except the first SYN packet. The network interface that is used to transmit a packet is the same interface that received the last packet.

IP Fastpath was not without faults, however. If you used asymmetric routing, you could run into issues:

Fast path not compatible with asymmetric routing

In a symmetric network, the destination MAC address of the response packet is that of the router that forwarded the incoming packet. However, in asymmetric networks, the router that forwards packets to your storage system is not the router that forwards packets sent by the storage system. Therefore, in asymmetric networks, you must disable fast path.

HSRP also could present problems.

http://dustydev.blogspot.com/2012/10/io-fastpathing-on-netapp-controller.html

Also, if you used certain types of NIC teaming on clients, you could also see problems because the NIC team would send the MAC address of the underlying NIC and ONTAP would try to send it to that same MAC, but when it hits the NIC team, the NIC that gets the request might not be the same one that sent it. For example:

https://community.netapp.com/t5/Backup-and-Restore-Discussions/HP-Network-Teaming-Performance-Issue-Connecting-to-Filer/td-p/52335

In fact, if there were occasions where fastpath could be disabled on interfaces if the connection determined there was a loss. Then the fall back was to use the routing table. If the routing tables were bad or incorrectly configured, you’d experience an outage. IP fastpath actually would mask latent routing issues.

(The takeaway you should have from this is that removing IP fastpath is actually a good thing.)

Impact of IP Fastpath Removal

There’s a really good KB article on the impact that can be found here:

https://kb.netapp.com/app/answers/answer_view/a_id/1072895

ONTAP 9.2 replaced fastpath with always-on route caching to maintain the same level of performance without the unforeseen headaches that could occur with asymmetric routing. However, if your network design relied on IP fastpath to route traffic and bypass bad routing tables (including dynamic and static routes), then upgrading ONTAP to 9.2 would make those issues come to light.

Or maybe you wanted to purposely ignore routing tables, such as what went on in this article:

https://community.netapp.com/t5/Data-ONTAP-Discussions/NetApp-Ontap-9-2-Upgrade-review-your-network-first/td-p/136657

Things to check before upgrading to ONTAP 9.2 (and later)

  • How is your routing table currently configured in the SVM? Are you using 0.0.0.0/0 default routes? (network route show from the CLI)
  • Compare your connected clients (network connections active show) to your current routes. Do all clients have a route to the appropriate SVMs?
  • Are there multiple routes with the same routing metric? If so, any of those routes may be chosen. Will any of them break connectivity?

In most cases, this change won’t cause an issue, but if you do see intermittent network connectivity, network performance degradation or other network related issues after upgrading to ONTAP 9.2, look at this change first and open a support case to get assistance.

If you have any questions, feel free to leave them in the comments and I’ll get them answered!

Behind the Scenes: Episode 127 – NetApp United

Welcome to the Episode 127, part of the continuing series called “Behind the Scenes of the NetApp Tech ONTAP Podcast.”

tot-gopher

This week on the podcast, NetApp United is looking for new members!

Image result for netapp united

We bring the head of the program, Petya Stefanova (@PeytStefanova) to give us a rundown, as well as some of the current NetApp United members to tell us about their experiences.

Included in the discussion:

Finding the Podcast

The podcast is all finished and up for listening. You can find it on iTunes or SoundCloud or by going to techontappodcast.com.

This week’s episode is here:

Also, if you don’t like using iTunes or SoundCloud, we just added the podcast to Stitcher.

http://www.stitcher.com/podcast/tech-ontap-podcast?refid=stpr

I also recently got asked how to leverage RSS for the podcast. You can do that here:

http://feeds.soundcloud.com/users/soundcloud:users:164421460/sounds.rss

Our YouTube channel (episodes uploaded sporadically) is here:

Behind the Scenes: Episode 126 – Komprise

Welcome to the Episode 126, part of the continuing series called “Behind the Scenes of the NetApp Tech ONTAP Podcast.”

tot-gopher

This week on the podcast, we bring in Komprise (@Komprise) CEO Kumar Goswami (@KumarKGoswami) to chat about data management and how their software helps get the most out of your NetApp storage systems!

komprise

For more information about Komprise, check out komprise.com!

Finding the Podcast

The podcast is all finished and up for listening. You can find it on iTunes or SoundCloud or by going to techontappodcast.com.

This week’s episode is here:

Also, if you don’t like using iTunes or SoundCloud, we just added the podcast to Stitcher.

http://www.stitcher.com/podcast/tech-ontap-podcast?refid=stpr

I also recently got asked how to leverage RSS for the podcast. You can do that here:

http://feeds.soundcloud.com/users/soundcloud:users:164421460/sounds.rss

Our YouTube channel (episodes uploaded sporadically) is here:

Behind the Scenes: Episode 125 – Machine Learning and ONTAP

Welcome to the Episode 125, part of the continuing series called “Behind the Scenes of the NetApp Tech ONTAP Podcast.”

tot-gopher

This week on the podcast, we invited Senior Technical Director Santosh Rao in to discuss his blog series on Machine Learning in ONTAP, as well as how NetApp is helping power the latest and greatest in data analytics technology.

You can find Santosh’s blogs here:

https://blog.netapp.com/addressing-ai-data-lifecycle-challenges-with-data-fabric/

Finding the Podcast

The podcast is all finished and up for listening. You can find it on iTunes or SoundCloud or by going to techontappodcast.com.

This week’s episode is here:

Also, if you don’t like using iTunes or SoundCloud, we just added the podcast to Stitcher.

http://www.stitcher.com/podcast/tech-ontap-podcast?refid=stpr

I also recently got asked how to leverage RSS for the podcast. You can do that here:

http://feeds.soundcloud.com/users/soundcloud:users:164421460/sounds.rss

Our YouTube channel (episodes uploaded sporadically) is here: