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PostPosted: Tue Mar 16, 2010 8:40 am 
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I posed the idea of running a "diskless" LinHES frontend install off of a USB memory stick on the 2nd page of this thread: http://knoppmyth.net/phpBB2/viewtopic.p ... 0c9c97226d

As opposed to hijacking that thread I though I'd create a new thread to discuss the merits of this idea.

I'll quote BigBoyStan from the linkned thread:

Big boy stan wrote:
This is an interesting concept. Has anyone ever run a Knoppmyth/Linhes frontend off a USB stick before? This could be an interesting alternative to diskless frontends. You can get a 4GB thumbdrive for less then $10. I have heard that flash drives have a limited number of read and writes so that may be a problem.


Newer flash drives use load balancing algorithms so that they aren't constantly hammering the same bits / sectors and they can also mask bits / sectors similar to the way hard disks can if those bits / sectors develop errors.

With the extremely low cost of USB flash drives they are almost disposable anyway and thanks to Cecil's amazing efforts re-installing a frontend in most cases can be done in minutes.

With current threads I'd think the drive would be out-dated long before it's worn out but even if then you wouldn't be out much.

I've been wanting to try this but since I only have one TV I haven't had much motivation.

Thoughts?

Martian

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PostPosted: Tue Mar 16, 2010 9:07 am 
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To take this a step further (and why not), I suppose that this could even be done as a backend for root with real hard drives for media.

One real advantage for this could the ability to have a "test" system on one thumbdrive and a "production" system on another thumb drive. Once the test system is up and running, do a Linhes & mythtv back up of the old "production" system and a restore to the new one. Should do wonders for the WAF.

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PostPosted: Tue Mar 16, 2010 10:22 am 
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Location: LA, CA
I twice tried installing R6 on a 4GB usb stick without success. I could get it started, but I think I ran out of space to install correctly. idk why this was the case, as it seems like it would be OK. I adjusted the settings to the smallest drive space setting. I would try again, but I don't have a larger stick that is free at the moment.

Might also reference here.


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PostPosted: Tue Mar 16, 2010 11:14 am 
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Location: Calgary, Canada
Too Many Secrets wrote:
I twice tried installing R6 on a 4GB usb stick without success. I could get it started, but I think I ran out of space to install correctly. idk why this was the case, as it seems like it would be OK. I adjusted the settings to the smallest drive space setting. I would try again, but I don't have a larger stick that is free at the moment.

FWIW, I have a frontend running R6.01 with just an old 4GB hard drive and there's plenty of room to spare.


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PostPosted: Tue Mar 16, 2010 5:47 pm 
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Location: LA, CA
paulsid wrote:
Too Many Secrets wrote:
I twice tried installing R6 on a 4GB usb stick without success. I could get it started, but I think I ran out of space to install correctly. idk why this was the case, as it seems like it would be OK. I adjusted the settings to the smallest drive space setting. I would try again, but I don't have a larger stick that is free at the moment.

FWIW, I have a frontend running R6.01 with just an old 4GB hard drive and there's plenty of room to spare.


Well I'm thinking back and I might have to adjust my comment in context of pure FE. I might have been trying to run BE and FE off of the 4G stick, and not a pure FE as this box also has a encoder card in it. Or else I borked the install elsewhere. Just my experience. :roll:


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PostPosted: Tue Mar 16, 2010 6:25 pm 
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I like this idea. I am currently using older hard drives in all of my front ends (hand me downs from my main big ass server). But I think flash drives have come down enough in price that I will use them at the next opportunity.

My main concern will be sufficient I/O speed. The memory speeds can vary widely on these things but I haven't determined what I/O speed is required for a front end. I'm guessing it is low.


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PostPosted: Wed Mar 17, 2010 12:22 am 
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I guess Im biased because I wrote the diskless frontend script, but what is this doing that diskless frontends dont (other than having another device that may fail).

The only reason I can see where this could be useful is where someone has already formatted their root partition too small to fit the nfs root for the diskless FEs. Otherwise, the disk is already sitting there, spinning in the backend, why not use it?


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PostPosted: Wed Mar 17, 2010 8:50 am 
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Location: Ottawa, Canada
Greg Frost wrote:
but what is this doing that diskless frontends dont (other than having another device that may fail).

It is a reasonable question. I have looked at diskless front end briefly (not your how-to specifically though) and I was concerned about:

1) set up complexity and ongoing maintenance and updates of each front end image. Once you set up an image, how much process is it to up date to the latest packages, themes, etc.

2) Boot up performance (initial discovery can take about 10s)

3) potential complexity in my environment which is networked with 3 backends running virtualized on my main server.

Feel free to correct my understanding.


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PostPosted: Wed Mar 17, 2010 10:30 am 
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christ wrote:
It is a reasonable question. I have looked at diskless front end briefly (not your how-to specifically though) and I was concerned about:

1) set up complexity and ongoing maintenance and updates of each front end image. Once you set up an image, how much process is it to up date to the latest packages, themes, etc.

2) Boot up performance (initial discovery can take about 10s)

3) potential complexity in my environment which is networked with 3 backends running virtualized on my main server.

Feel free to correct my understanding.


1) You update on the server first. This will download all the pacman packages and install just on the server. Then on the diskless clients you update but since the pacman cache directory is NFSed. it only has to install, not re-download packages. Pretty simple and easy.

So for me the diskless clients are great (thank you Mr Frost for that work).

But it would be interesting to see how booting from flash would work. I would think the local theme/image caching would exercise it pretty good. Especially the newer themes that use Fanart/posters in watch recordings and mythvideo. It would be interesting to see how it behaves.


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PostPosted: Wed Mar 17, 2010 11:10 am 
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djb61230 wrote:
1) You update on the server first. This will download all the pacman packages and install just on the server. Then on the diskless clients you update but since the pacman cache directory is NFSed. it only has to install, not re-download packages. Pretty simple and easy.

interesting. The cache is no issue for me as I have this on my firewall anyway with squid. But to make sure I understand your point, once the image is set up, to update a front end, I just boot the front end and update from the front end as normal and the changes will be updated on the hosted image. Is that correct?

So in other words once the diskless environment is set up, you operate it as if it had a disk.


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PostPosted: Wed Mar 17, 2010 12:15 pm 
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Exactly.


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PostPosted: Wed Mar 17, 2010 12:21 pm 
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perfect. What is your experience with (2) in regards to discovery of the diskless image? From reading, PXE/BOOTP look like they will take about 10s before loading will begin.


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PostPosted: Wed Mar 17, 2010 1:03 pm 
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Well I run my clients all the time so rebooting is infrequent. I would guess the discovery is 2-3 seconds and it's loading the kernel. It still takes time to boot and start the frontend though. I have never timed it nor fine tuned it from what the script sets it up to run. I could time it and report back if that is useful information.

As mentioned earlier, you do need space on / to have the client file systems. When I installed R6 last summer the "default" size for root was 5gb. Knowing I was going to have up to 5 clients I maxxed out the size the install would allow (25gb I think) for root. I think I use about 70% of root. These numbers are from memory so they could be a little off :)


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PostPosted: Wed Mar 17, 2010 6:38 pm 
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djb61230 wrote:
I could time it and report back if that is useful information.

If it is easy then sure but I expect actual boot time will vary by processor and bandwidth. I currently run most of my front ends on Core2 8500's (ie. 3.1GHz dual core) over 100Mb links though I'll probably move these to GigE before long.

I'm not sure what the process is that it uses (ie. tftp the image or treats the host as a virtual disk; I guess I should read Greg's script). If the latter then I would think the ethernet bandwidth would not be much of an issue so the delay would be from the moment the BIOS decides to BOOTP to the moment it starts loading. So perhaps the only useful part would be from when BIOS BOOTP's to the point LILO runs.

djb61230 wrote:
As mentioned earlier, you do need space on / to have the client file systems.

I have 15TB of disk space... is that enough? ;-)


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PostPosted: Thu Mar 18, 2010 12:07 am 
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christ wrote:
djb61230 wrote:
I could time it and report back if that is useful information.

If it is easy then sure but I expect actual boot time will vary by processor and bandwidth. I currently run most of my front ends on Core2 8500's (ie. 3.1GHz dual core) over 100Mb links though I'll probably move these to GigE before long.

I'm not sure what the process is that it uses (ie. tftp the image or treats the host as a virtual disk; I guess I should read Greg's script). If the latter then I would think the ethernet bandwidth would not be much of an issue so the delay would be from the moment the BIOS decides to BOOTP to the moment it starts loading. So perhaps the only useful part would be from when BIOS BOOTP's to the point LILO runs.

djb61230 wrote:
As mentioned earlier, you do need space on / to have the client file systems.

I have 15TB of disk space... is that enough? ;-)


:shock:

NICE!


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