[mythtv-users] Diskless backend?

[Ray Olszewski]

I don't run nfs at the speed you wonder about, but I routinely transfer via 
Samba and ftp at rates way above 8 Mbps. (So do a lot of people, I'm sure.) 
Over CAT5 100 Mbps connections, I routinely exceed 50 Mbps, sometimes hit 
70 Mbps, on sustained transfers. Id' be surprised if you were to need 
either fibre or gigabit to handle the load you describe, unless you scaled 
up quite a bit further then you seem to be contemplating.

Whether the backend host is up to the task is a different questions, but 
that is just the usual question of calculating your needs against disk 
transfer speeds, disk buffer sizes, and CPU (and, I suppose, choosing a 
decdnt NIC, since some drivers seem to load the CPU more than others).

My skepticism about this idea comes from looking at its economics. I 
suspect you would do better cost-wise to have each backend store its video 
locally, and if you needed to share it some way other than through 
mythfrontend's ability to access multiple backends, just use samba or nfs 
to export the relevant directories. That's how I handle my DivX captures 
here, though I haven;t set Myth up to work that way yet.

At 06:12 PM 6/22/2003 -0400, Joseph H. Fry wrote:
>If it were me, I'd probably use Gigabit copper to the storage machine if
>possible... that way you could use multiple backends that utilize the
>same storage device... I'm pretty sure their ring buffers would have to
>be located in different folders, but they could at least have access to
>the same recorded shows (I should think anyway)
>
>Of course your storage machine will need to be gigabit, which most
>"non-upgradeable" NFS machines aren't, unless they are recent.
>
>Or you could just put multiple net cards in the storage device and using
>crossover cables network them direct to the backend machines... a little
>private network between devices, so your frontend traffic wouldn't
>interefere with data to your nfs machine...
>
>HMM... I've been planning to do the same thing... I got a steal on a 6
>drive ATA-33 raid 5 NAS machine... of course it only has one 10/100
>network port on it, but I can go directly scsi from it as well (it has
>integrated scsi to ide raid converter.  I haven't loaded drives in it
>yet, so I don't know if it will handle the 100+gb drives I want to use,
>but I got it for $200 without the drives, so even if it's limited to
>small drives it's still cheaper than a machine with a 6 drive raid card.
>
>Please keep me updated on what you end up doing... look into gigabit,
>it's come down in price a lot... hell they had a whole section (half an
>isle) dedicated to it at my local compUSA... a year ago you would never
>find it retail.
>
>-----Original Message-----
>From: mythtv-users-bounces at snowman.net
>[mailto:mythtv-users-bounces at snowman.net] On Behalf Of Max
>Sent: Sunday, June 22, 2003 4:57 PM
>To: MythTV Users List
>Subject: [mythtv-users] Diskless backend?
>
>I've been pondering going diskless on front AND backend (store all data
>on NAS). The frontend is easy and I am sure plenty of people are doing
>it, however I am wondering how practical is it on the backend. At around
>4GB per hour with higher quality, it works out to be about 8Mbits/s
>worth of raw data. Add overhead and all and double for playback, this
>will clearly not work with 10baseT and wireless, but theoretically
>should not be an issue on a "no-collision-domain" 100Mbit (I think the
>figures I seem to recall is about 40Mb/s sustained data transfer on
>100Mbit copper, a bit more on fiber. Plus I am wondering if NFS can even
>handle this sort of the data without severe load increase on the server
>and client.
>
>... or I could be overly paranoid and it may work just fine.
>
>Anyone played with this sort of a setup? Any experiences?