Fibre Channel Switches

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uunix
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Fibre Channel Switches

Unread postby uunix » Sat Nov 19, 2016 10:21 am

Does anyone have any experience with these. It's something I have never even looked at before , but considering I have a massive amount of space on a fibre array and have had to remove 7 of the 9 disks due to restrictions with StoneFS (no point running 9 disks worth of electricity if you can only use 2, I'm wondering if this would be a better option.

Yes I'd need FC cards for any other client of the switch but that's no problem. I will guess though that if I bought the faster switches, it would be backward compatible with the slower speeds of the FC in my octane etc?

To summarize, I know nothing about these switches.

Anyone have experiences using FC Switches with SGI et al ?
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Re: Fibre Channel Switches

Unread postby jan-jaap » Sat Nov 19, 2016 2:41 pm

I've used SAN switches with my SGIs for years. Currently I'm using a Brocade 5000, a 32 port 4Gb switch.

The simple FC case is 1 host to 1 simple JBOD array. It's called FC-AL. This is your average Discreet setup. The advantage of FC here over SCSI is IMHO the use of fibre which means the array can be far away :)

A SAN shares storage between multiple hosts, but this storage is a SAN server, not a JBOD. A SAN server can configure volumes and share them out to hosts, among many may other things.

A SAN switch has more capabilities than most ethernet switches, it can also configure who gets to talk to who etc. Depending on your switch and it's licensed features you can trunk ports, route FC over ethernet to a remote site etc etc.

A couple of things to keep in mind:
1. SAN switches are usually 1U and can be unbelievably loud. I used to have a Brocade 2Gb switch which was totally unbearable.
2. Most switches in the 4Gb generation have for example 16 or 32 ports, but half of them won't work unless you but a license to enable them. Newer switches also won't accept just any GBICs, but require the expensive ones of the original vendor. If the password to the switch and the it's bootrom are unknown you'll need the manufacturer to unlock it and they won't do it unless you get a service contract first.
3. SAN servers are the same: you may find one which takes SATA disks in brackets with FC-SATA adapters, but the adapters only talk to half a dozen types of SATA disks, now 10 years old and impossible to find. They require licenses for interesting features (snapshots, replication, ...).

If you want to get into SAN hardware you should read a book first to get the concepts.
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Re: Fibre Channel Switches

Unread postby uunix » Sat Nov 19, 2016 3:02 pm

jan-jaap wrote:I've used SAN switches with my SGIs for years. Currently I'm using a Brocade 5000, a 32 port 4Gb switch.

The simple FC case is 1 host to 1 simple JBOD array. It's called FC-AL. This is your average Discreet setup. The advantage of FC here over SCSI is IMHO the use of fibre which means the array can be far away :)

A SAN shares storage between multiple hosts, but this storage is a SAN server, not a JBOD. A SAN server can configure volumes and share them out to hosts, among many may other things.

A SAN switch has more capabilities than most ethernet switches, it can also configure who gets to talk to who etc. Depending on your switch and it's licensed features you can trunk ports, route FC over ethernet to a remote site etc etc.

A couple of things to keep in mind:
1. SAN switches are usually 1U and can be unbelievably loud. I used to have a Brocade 2Gb switch which was totally unbearable.
2. Most switches in the 4Gb generation have for example 16 or 32 ports, but half of them won't work unless you but a license to enable them. Newer switches also won't accept just any GBICs, but require the expensive ones of the original vendor. If the password to the switch and the it's bootrom are unknown you'll need the manufacturer to unlock it and they won't do it unless you get a service contract first.
3. SAN servers are the same: you may find one which takes SATA disks in brackets with FC-SATA adapters, but the adapters only talk to half a dozen types of SATA disks, now 10 years old and impossible to find. They require licenses for interesting features (snapshots, replication, ...).

If you want to get into SAN hardware you should read a book first to get the concepts.

jan-jaap, that's highly informative, thanks.
I did notice on ebay there were many that said for example, 16 port, 8 active, which is obviously a licencing restriction.
In my case the switch would connected to Sun StorEdge T3 + possibly 2 or 3 clients. My Discreet Octane is currently connected directly to the T3.

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Re: Fibre Channel Switches

Unread postby jpstewart » Tue Nov 22, 2016 1:36 pm

A couple of points to add to what jan-jaap already said:

The fibre channel switches I've seen are backwards compatible for two generations. So a 4Gbps unit can be expected to support 2Gbps and 1Gbps, but an 8Gbps switch may not support 1Gbps (which is what the T3 runs at, IIRC).

With a SAN setup, you can easily partition the T3 to have a different filesystem for each of the clients. You cannot easily share a single common filesystem among multiple clients unless you're using a cluster filesystem such as CXFS. Beware the licensing costs and difficulties with CXFS! (There are open-source cluster filesystems on Linux but they're not supported under IRIX, AFAIK.) Good old NFS is simpler if you need multiple clients to have access to the same filesystem.

Based on my own experience, I'd suggest reading the manual and anything else you can find on Google for any SAN hardware (switch or storage) you're interested in before you buy. That way you'll know ahead of time if you need expensive (or impossible to get) licenses, management software, or support contracts. Assume any gear you get will have old passwords. Fortunately, there was a well-documented way to reset the passwords on my switches using a serial terminal without erasing the existing licenses for add-on features. Some sellers will reset passwords and/or itemize installed licenses. Then they'll charge extra. Other sellers who aren't so familiar with SAN hardware will offer much lower prices for as-is hardware with unknown passwords. If you know how to reset passwords yourself and are willing to take a chance on what extra licenses are installed, great deals can be had. So I highly recommend reading about whatever specific hardware you're looking at.
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Re: Fibre Channel Switches

Unread postby uunix » Tue Nov 22, 2016 1:41 pm

Nice one jpstewart, and in particular the backwards compatibility statements. I may have got stung on that one.
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Re: Fibre Channel Switches

Unread postby uunix » Wed May 17, 2017 7:57 am

Well, I went and purchased a very very cheap Silkworm 3850, I thought it's a good gamble to get my hands dirty, understanding that it probably hadn't got the admin/root password.
It arrived today, I powered it up and tried connecting to the serial, no joy there. Correct cables are at home.
So I connected it to a small network hub along with my Origin and ran 'snoop' watching for any addresses and viola, in a few seconds, 10.10.10.33 was asking whois 10.10.10.1..
Then I set my windows box to have an additional IP in that range, and tried to open up the web front end, no joy, the java was out of date and I'm not messing with policy settings to allow it, so I used putty to telnet in and bingo.. telnet session..
But alas no default passwords worked and I don't have a support contract, so it would be painful to get a reset image.
Then I read about taking out the flash card and resetting the password files with a flash card reader, which I have at home. So I have taken the unit apart and have the flash drive. The process is just replacing the /etc/passwd files in both partitions with the passwd.default file.
Now, I do have a USB flash reader, but the writer of the instructions stated you required a LINUX machine. Alas, I do not have one, but does anyone know, if a USB flash drive reader would work in my FUEL with 6.5.30 installed?
If it doesn't I'll just build myself a LINUX box, but I would rather not.
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Re: Fibre Channel Switches

Unread postby jan-jaap » Wed May 17, 2017 8:53 am

You should really use the serial port. I'm not sure the port is PC DB9 compatible, you may have to create your own cable.

The trick is essentially to boot it in single user mode from the boot rom. If the boot rom is password protected and prints out a boot password recovery challenge I can solve that puzzle 8-)

Be careful not to scramble the CF card, because the feature license strings are stored on it.
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