Meraki Aggregation Switches Vs Storage Area Network Switches

[mugrene]

Greetings;

We are planning to buy a SAN Switch - Storage Area Network Switch that will be used for servers and storages

Because we are migrating to Meraki Products, We are wondering if we can use one of Meraki Aggregation Switches.

Is Aggregation Switches work like Storage Area Network Switches?

Kindly advise.

Regards;

[Bruce]

A SAN switch is generally a Fibre Channel switch rather than Ethernet. The Meraki switches are all Ethernet. Are you talking about Fibre Channel when you refer to a Storage Area Network?

[cmr]

@mugrene If you are referring to an iSCSI switch then Meraki switches can handle that traffic, but it really does depend on how many servers and SAN nodes you have, along with the characteristics of each.

The most common iSCSI switch requirements are jumbo frames (over 1500 bytes) and large buffers on each port.  However we do have a number of iSCSI SANs and the vendor we use (Pivot3) does not use jumbo frames and as long as you have the hosts and storage nodes connecting at the same speed then the buffers are not so important.

[GreenMan]

I personally would recommend looking at Nexus Data Centre switches, with larger buffers.

Most decent enterprise switches will run a lightly loaded iSCSI / NFS SAN OK - particularly if you ensure the SAN itself has a higher capacity uplink than the hosts it is serving, but bear in mind that, when you start to over-subscribe target ports (e.g. multiple servers writing to the same SAN port) buffers overflow quickly and packets are dropped.   SAN protocols generally behave poorly with even fairly low levels of packet drops.

Of course, DC switches tend to be more expensive, so 'you pays your money and takes your choice'

[PhilipDAth]

>I personally would recommend looking at Nexus Data Centre switches, with larger buffers.

@GreenMan , you might be surprised how small the buffers are on some of the Nexus switches.

The Nexus 3548 (with 48 x 10Gbe ports) has a total of only 18MB!  That's an average of just 384KB per port.  At 10Gbe - that disappears pretty quickly.

https://www.cisco.com/c/en/us/products/collateral/switches/nexus-3548-switch/data_sheet_c78-707001.h... 

Buffer size

6 MB shared among 16 ports; 18 MB total

They basically rely on everything being 10Gbe.  If you 1Gbe connected iSCSI port and 10Gbe connected storage you very quickly run into problems.

The Meraki MS425 doesn't look so bad now ...

[GreenMan]

I must admit, it's been a while since I sold Nexus, but I remember that being a thing - which is why I mentioned larger buffers specifically.  Not sure how that pans out in the current Nexus range...

[cmr]

Has anyone here actually seen issues with iSCSI switches that as mentioned above can happen?  I ask as the switches we use are HP or Cisco 10-12 port ones for ~£800 each.  We don't overload them but do have up to 7 ports connected with two being server only, three being server and storage and two being storage only.  Data rates average about 400Mb/s writing but a lot of the data is video streaming so pretty constant rate.  Reads are much less.

The only issues we see are cabling issues with Dell 10GbE Cu ports not liking most cable connectors...

[GIdenJoe]

Isn't the MDS line the SAN switch line instead of the Nexus which is more ethernet LAN?

I can't seem to find any exact buffer numbers only buffer credits which I am unfamiliar since no dc guy 😜

[PhilipDAth]

Correct.

[KarstenI]

There is one more significant reason that I would not use a Meraki MS as a SAN-switch. When the SAN-switch restarts (for example because of an update) you unplug the HDs from the servers. I prefer to have different update cycles for my storage and my campus. Yes, a separate network would help, but I don't want to see "critical update" for a too long time in the Firmware Update section.