ethernet frame size / MTU

Question

ethernet frame size / MTU

I'm setting up NAS at my house, using two different systems. I'm using a Buffalo NAS (4TB) and a Drobo FS with 17 TB.

I'm finding that the transfer speed is surprising slow through ethernet. Keep in mind I'm not a technical person. My surprise is that I thought ethernet setup would increase the speed to something manageable time-wise.

For example, I want to transfer around video files from one computer to another, I'm surprised it takes so long.

I've run a variety of tests, done some reading on these forums and around the net, and have found that it appears a typical home network via ethernet is about 15-20 MB/sec, more or less. Hope I wrote that mb/sec correctly.

Anyways, I've been surprised a bit that ethernet isn't faster than this. When I did a direct connect of my Drobo FS via ethernet to my macbookpro, I'm transferring over my Aperture library. About 400 gigs. This is taking around 30 hours.

Is this a real world scenario and I need to just get over it? I guess I thought that ethernet would be faster. Keep in mind, I'm not a technical person, so I don't really know what I'm talking about or expected. I suppose when I went to wire my house for the fastest possible connections, I was thinking it wouldn't take nearly 2 full days to transfer my Aperture library for backup, etc.

I have been playing around with MTU a bit. Set at 9,000 for the Drobo. I notice that I can only set the MTU to 1500 in my macbookpro. Wouldn't that speed up things with a direct ethernet cable connection between the Drobo FS and the macbook pro if the laptop were to be able to move the data in larger chunks (jumboframe 9000)?

Not sure if I'm wording all this correctly. I was hoping to increase the MTU to 9,000 on the MBP, but seem to be limited to 1500. Any thoughts on that?

Is there any way to increase speed beyond ethernet or is that going to be a real world cap for the average home user?

Thanks

Macbook pro i7, Mac OS X (10.6.6), 8 GB ram

Posted on Mar 19, 2011 1:36 PM

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Answer 1

Mar 19, 2011 3:01 PM in response to Texas_Man_Luvs_His_mac

About 400 gigs...is taking around 30 hours.

Is this a real world scenario and I need to just get over it?

It takes me <1 min per GB to transfer large files to my Drobo FS over a gigabit ethernet connection. Transfer rate is about 25-30 MB/sec. I tend to see a relatively long pause (10 sec?) between files, so if you are transferring lots of little files that could be a factor. 400 GB of large files should take <7 hours, it could be as fast as 3 to 4 hours.

Have you verified what speed your computer and NASs are connected at and if so is it 1 Gb/sec?

Is this a real world scenario and I need to just get over it?

For 10 Mb/sec ethernet it would be reasonable, but not gigabit ethernet.

Wouldn't that speed up things with a direct ethernet cable connection between the Drobo FS and the macbook pro if the laptop were to be able to move the data in larger chunks (jumboframe 9000)?

I'm not sure. My Drobo FS is set to Automatic.

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Answer 2

TeenTitan

Level 4

2,640 points

Mar 19, 2011 3:06 PM in response to Texas_Man_Luvs_His_mac

when you connect directly to the Drobo FS, over ethernet, if you set ethernet to automatic configure, what dose it configure to? (speed, Duplex, MTU)

NAS Buying Guide did a review of the Drobo FS. Part of their review was a performance test. If you look at the test results they show that NAS Buying Gudie's test teem found the copy files to Drobo FS to average 19.3 MB/s. Witch interestingly enough seems to be the same speed your reporting.

Promise SmartStor DS4600 4x1TB RAID System Witch isn't a NAS; but direct connect storage, offers eSATA 3G witch maxes out at 220MB/s. on a 17-inch MacBook Pro, with eSATA adapter it would probable max out around 120 to 180 MB/s.

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Answer 3

Mar 19, 2011 7:49 PM in response to TeenTitan

thanks for the responses.

I just did a transfer of a 3.96 gb file from the drobo fs to my laptop. It isn't direct connected, but through the gigabit D-link. It took 1 minute 51 seconds. IF I did the math right, that would be about 36mb/sec.

That doesn't seem all that unreasonable, I suppose. I'm guessing this is about normal?

Now, the real issue for me, is the following: it's all about Aperture. The Aperture file just creeps along. Actually, it seems to be hanging the last couple of attempts to get it to transfer. I copy the file, then paste it to the drobo folder. It never starts transferring.

It used to start transferring. Last attempt was about 2 days ago, after almost 24 hours of time, it hadn't gotten to 1/2 the 300+gb file.

I'm not sure why, but I notice that this one file, the aperture database file, seems to act different.

When I go to copy other large files, such as my user file (400 gb), it doesn't hang and seems to transfer faster.

I verified that the ethernet advanced settings show a manual configuration of 1000baseT, full-duplex, and standard (1500).

Why isn't there an MTU of 9,000?

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Answer 4

red_menace

Level 6

17,066 points

Mar 19, 2011 10:12 PM in response to Texas_Man_Luvs_His_mac

A 1500 byte packet is the largest allowed by standard Ethernet, so that is what is used pretty much everywhere. A 9000 MTU would be jumbo frames, which will be specific to that particular network.

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Answer 5

Mar 20, 2011 4:17 AM in response to red_menace

Does OS X support jumbo frames?

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Answer 6

red_menace

Level 6

17,066 points

Mar 20, 2011 8:51 AM in response to Texas_Man_Luvs_His_mac

The OS itself does, but this is usually a hardware issue (i.e. the Ethernet chipset used). My 2008 MBP uses the Marvell Yukon Gigabit Adapter 88E8055 Singleport Copper SA, and I can select jumbo frames from the advanced Ethernet preferences (after choosing to configure manually). The technical specifications from Core 2 Duo machines such as the Mini still show that they support jumbo frames, so if you do not even have that option, my guess is that the chipset used in your machine does not support it.

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Answer 7

Mar 22, 2011 7:02 AM in response to red_menace

Thanks for the information.

I guess the thing I'm looking at now, the big question for me, is what is the fastest possible method to transfer data off of a computer to some other source? Is Ethernet basically as good as it gets?

For almost all of what I do, the ethernet speed is alright.

The one thing that seems to stump me is the transfer of my aperture library. It just doesn't play nice. That one file seems to either

#1 - hang and not transfer at all, which is most common. Not sure why, it never gets beyond the "preparing to copy" stage

#2 - once it transfers, it seems that file doesn't want to transfer fast.

I'm not sure why, but it is so slow or impossible for me to get a decent copy of my aperture library.

I want to be able to keep a backup on my drobo, frequent backup that is updated weekly or maybe even twice weekly. But it is taking up to 2 days to transfer the data on that one file, when it decides to transfer.

I have been able to use an external drive with firewire 800 and make a transfer of the file in about 4 to 5 hours. I suppose that isn't too bad overall. I'm still surprised, though, that the ethernet/drobo setup isn't at least as fast as firewire 800, but it doesn't even come close. Not even when I direct connect the drobo to the laptop. Not sure why that is.

Any insight, ideas, etc are appreciated. Basically, can anyone give ideas on managing transfers of files in the 500 gb range, what might work. I'm open to about anything at this point, other ideas, different kinds of media, etc.

Robert

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Answer 8

Mar 25, 2011 7:22 PM in response to Texas_Man_Luvs_His_mac

I decided to try forklift 2. Nice program. I started a transfer of my Aperture file 24 hours ago. It still says "Calculating" in the indicator bar. 24 hours of calculating?

That is what the finder does at times also.

What in the world goes on with the aperture file that it seems immune from transfer from one location to the next?

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Answer 9

satcomer

Level 4

1,593 points

Mar 25, 2011 8:33 PM in response to Texas_Man_Luvs_His_mac

Check your Ethernet cables? If you want the fastest Ethernet cable seed use CAT 6 Ethernet cables.

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Answer 10

Mar 25, 2011 8:50 PM in response to satcomer

I purchased all brand new cables that are cat6, so that shouldn't be a factor.

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Answer 11

Apr 9, 2011 7:44 AM in response to Texas_Man_Luvs_His_mac

I contacted Drobo to get help with what I perceive are slow transfer rates. Keep in mind I am self taught at all of this and new to all of this, so I might just be missing something obvious like gigabytes of data take a long time to transfer. At any rate, I'm really hoping to increase the speed of data transfer.

#1 - I've verified I have cat6 cables from all computers to the wall connections
#2 - I've verified that Verizon used Cat 5e cables from wall to wall connections. Would this slow down data transfer much?
#3 - I've done a variety of diagnostics with Drobo's guidance. Still waiting to hear back from them. I can't seem to find a way to attach screen shots or files on this forum, but here's what I can put into words:
--> when the drobo FS is directly connected via ethernet to my computer with cat6 cable, it reveals a data transfer rate of 60.7 read/31.4 write for a 128 MB file, 6.8 read/5.5 write for a 256.0 MB file, and 15.6 read/7.5 write for a 512 MB file size. This was information provided by AJA System Test

I have some system logs and drobo logs I could paste on here if someone would be able to interpret them.

I'm guessing that using an external drive with firewire 800 is still the overall best option. Seems to work much faster at transferring data than a directly connected Drobo Fs.

Is this as good as it gets for a home user? Is there a way to amp up data transfer?

Appreciate your response.

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