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Build your own affordable SAN -- that works! Discussions

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Christian Betong
Build your own affordable SAN -- that works! Discussions
on Aug 27, 2008 at 12:18:30 pm

Hi there!

Trying to move over the discussion of the article written by Bob Zelin about building a MetaLan "SAN" with off the shelf hardware.

The original Article is here:
http://library.creativecow.net/articles/zelin_bob/build_your_own_san.php

I have some questions about this setup compared to just setting up a NAS.

Right now I have a server with a 4port gigabit card. It has a RAID with aroung 600MB/s read. The clients are connected straight to the card, not going through a switch. I am getting decent speeds copying data(75MB/s) but bad data rate when playing from within FCP(35MB/s). Also, writing to the server i only get aroung 30MB/s. This is probably due to a bad setup on my part.

For people with similar setups(ie not MetaLan) what kind of speeds do you get and how many clients can you handle in this way simultanous?

For you with experience with MetaLan, what is the benefits of metalan over normal AFP over gigabit setup?

Best regards

Christian


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Matt Burnell
Re: Build your own affordable SAN -- that works! Discussions
on Aug 27, 2008 at 3:41:34 pm

What server are you using for your setup? I've heard upgrading to OSX 10.5.4 helps substantially.



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Bob Zelin
Re: Build your own affordable SAN -- that works! Discussions
on Aug 28, 2008 at 11:07:09 pm

You may have a 4 port ethernet card, but if you don't have a managed switch that is hooked up to your 4 port card, and have it configured for link aggregation, you will fail. You have not described your equipment. What is your server, what is your switch, what is your operating system. Just having OS-X 10.5.4 and a 4 port card will do nothing for you without a managed gigabit ethernet switch that SUPPORTS LINK AGGRETATION - and you have to set this up in the menus - it just doesn't "work" when you take it out of the box.

I use Small Tree, because they help me on the phone. I was going to use the NetGear GSM series managed switches, but I could not get someone on the phone to help me set up the link aggretation. That is why I chose Small Tree.

Bob Zelin




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Eric Mittan
Re: Build your own affordable SAN -- that works! Discussions
on Aug 31, 2008 at 5:12:41 am

I have a few follow-up questions.

If it were within the budget of the project to do so, would having 2 four-port ethernet cards installed on the server be worth it? I understand link aggregation, I'm just wondering if with the first four ports you hit any sort of performance ceiling on the hard drives. Bob, since you're using a Mac Pro, can you also aggregate one or both of the on-board gigabit ports on the Mac Pro along with the 4 from the card? Would that add any worthwhile performance?

Similarly, might it be worth it if the clients had a slot free for them to put 4 port cards in the clients and aggregate their connection to the SAN? And again with the possibility of throwing in either or both of the onboard connectors on top of a 4 port card...would that be worthwhile?

I'm just asking with the scenario in mind of what the possibilities would be if you already had a 48 port managed switch but you only needed to connect a server and 3 clients.


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Bob Zelin
Re: Build your own affordable SAN -- that works! Discussions
on Aug 31, 2008 at 1:41:58 pm

No, no and no.

you write -
would having 2 four-port ethernet cards installed on the server be worth it?

REPLY - your bandwidth would not increase. Small Tree sells 4 and 6 port cards. I have clients running with 6 FCP systems - all ProRes422 HD on a 4 port card with a 24 port switch. MAC Pro only has 4 Gig of RAM, and there are no issues.

you write -
I understand link aggregation, I'm just wondering if with the first four ports you hit any sort of performance ceiling on the hard drives.

REPLY - no. The drive performance is LOCAL to that central computer. It's running at 500mb/sec. You use ethernet to access these drives via the switch, and the limitation of the bandwidth -even with Jumbo frames - is 70mb/sec - NO MATTER WHAT YOU DO (unless you switch to 10Gig ethernet). You do not need more than this bandwidth for any SD resolution, or DVCProHD or ProRes422HQ.


you write -
Bob, since you're using a Mac Pro, can you also aggregate one or both of the on-board gigabit ports on the Mac Pro along with the 4 from the card? Would that add any worthwhile performance?

REPLY - you can, but I use the local MAC Pro ports for local internet and email support. If I wanted 6 ports aggrigated, I could buy the 6 port Small Tree card for $140 more.

you write -
Similarly, might it be worth it if the clients had a slot free for them to put 4 port cards in the clients and aggregate their connection to the SAN? And again with the possibility of throwing in either or both of the onboard connectors on top of a 4 port card...would that be worthwhile?

NO - as per the Small Tree site -

Q: Can you trunk with link aggregation from the server to the client and go twice as fast?
A: No. This is a common misconception. Many inexperienced Apple resellers will make this mistake, which is why you want to talk to a networking expert before installing any serious infrastructure.

Link aggregation works by load-balancing “sockets” (referred to in the IEEE 802.3ad spec as “conversations”) over all of the available ports. On a server, this works wonderfully since a server might have 10 clients connecting. Each of these 10 sockets can be routed over a different port, providing an evenly-loaded network with a higher aggregate bandwidth.

Clients generally connect to one server. Hence, if you run link aggregation on a client, this one socket (conversation) will run over one of the ports. You might see some traffic on the second port if you’re also checking e-mail or viewing web pages, but you won’t see 2X the bandwidth to the server. Some people implement link aggregation on clients, but it’s primarily for redundancy (fail-over capability).



you write -
I'm just asking with the scenario in mind of what the possibilities would be if you already had a 48 port managed switch but you only needed to connect a server and 3 clients.

REPLY -
what about it? Your 48 port managed switch MUST support IEEE 802.3ad
which is the LACP protocol. If it does not (and many don't) it wont work. If it does, you take 4 or 6 of those ports, go to a multi port card in your "server", link aggregate, and you are done. Plug in your MAC FCP systems with one single ethernet cable, assign a static IP, set Jumbo frames, and START EDITING HD ! If you only have 3 clients, then you have a LOT of spare ports for the future.

Bob Zelin




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Simon Blackledge
Re: Build your own affordable SAN -- that works! Discussions
on Oct 14, 2008 at 7:22:40 am

70MBs max?

grab from a 4bay enhance over single gig-e

http://2.bp.blogspot.com/__OQ7QUrRrWA/SOyZQ9K8_HI/AAAAAAAAAFc/FFJdlM7Z7-0/s...





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Chris Blair
Re: Build your own affordable SAN -- that works! Discussions
on Oct 14, 2008 at 3:10:47 pm

[Simon Blackledge] This shows speed over single Gig-E from a server to client using a single EnhanceTech 4Bay. Was quite suprised with the result. AJA test showed similar.

From all the folks we've talked to, you cannot solely rely on disk read/write speed tests to determine if a SAN or NAS setup will allow you to reliably capture and edit video.

Have you captured and edited with this setup without issue?

There are things like latency and jitter (don't ask me what they mean...only IT engineers know!) that can affect performance beyond sustained read/write speeds. So while a DIY setup may indeed work. You can't solely rely on a disk test to make that determination.

As an example, our Apace vStor originally tested at around and 55-65MB/sec for read. But we were able to get 4 real-time, uncompressed video channels stacked one on top of the other, each with a DVE move...with that segment copied and looped for 10 minutes. During all this, another workstation could edit a couple channels of DVCPro50 footage (about 8MB/sec each) without any dropped frames, pauses or stutters.

Theoretically, we were moving 20MB/sec per channel x 4 channels = 80MB/sec; plus 8MB/sec on 2 channels = 16MB/sec. So that's 96MB/sec. and that's not taking into account any overhead needed to process all this. All that when the disk speed tests showed sustained speeds of only 50-60MB/sec.

I'm all for DIY systems if they work and are reliable...so I'd be interested to hear how the system works in an editing and capturing environment.

By the way...with some software tweaks from Apace, we were able to increase both our read & write speeds by about 20-30% over what's listed above. So we get nearly 100MB/sec write, and about 75-85MB/sec read speeds.


Chris Blair
Magnetic Image, Inc.
Evansville, IN
http://www.videomi.com


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Eric Hansen
Re: Build your own affordable SAN -- that works! Discussions
on Nov 3, 2008 at 11:21:36 pm

hey bob

as i understand it from Tiger's site, link aggregation works by opening a new connection for every request coming to the server from a client. so would it make sense to get a card (or cards) with as many ports as there are concurrent edit suites requesting media? ie, get a 6 port card for the server because there are 6 edit suites running at once. and if that's the case, is there a limit to the number of ethernet ports a Mac Pro or Tiger's software can support?

thanks

e

4 G5s, OSx 10.4.11, Final Cut 6.0.2, Kona LH (v5.1)
Xsan: Xserve 2.0 G5, 3GB RAM, 2 7TB Xserve RAIDs, Sanbox 5200
Quantum SDLT600A
decks: Sony HDW-M2000/10 HDCAM, HVR-M10U HDV with HD-Connect, DSR-1500 DVCAM, UVW-1800 BetacamSP
MacBook Pro: 2.33, 2GB RAM, OSx 10.4.11, Final Cut 6.0.2
cameras: Panasonic HVX200, Sony FX1 and A1U, Arri S/B 16mm
skis: Volkl Gotama 183s with 914s and Lange Fluid 120 boots


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Jeff Smith
Re: Build your own affordable SAN -- that works! Discussions
on Dec 3, 2008 at 11:19:17 pm

BoB said: "...you take 4 or 6 of those ports, go to a multi port card in your "server", link aggregate, and you are done."


Bob, I have the Smalltree PXG4 card and HP Procurve 1800 series 24-port switch. Isn't the link aggregation set in the switch software and not the card software?

Thanks,

Jeff



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Bob Zelin
Re: Build your own affordable SAN -- that works! Discussions
on Dec 3, 2008 at 11:27:17 pm

Hi Jeff -
I mean no offense by any comment that I may make here.

The ProCurve 1800-24 needs to have 4 ports link aggregated together, and jumbo frames enabled. Do you know how to do this ? You won't figure this out by just poking around. Do you know the settings (I sure don't and would love to know what they are for this specific switch).

Same with the Small Tree PEG4. Once the card is in the server MAC, you have to go to System Preferences/Network, and create a new link aggregate, call it bond0, and disable the 4 individual ports. Do you know how to do this ? Do you know how to enable jumbo frames in OS-X 10.5 with a link aggregate port ?

You can email me directly at maxavid@cfl.rr.com

bob Zelin




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