Re: RamDisk size for HVS-2


Ernst Lobsiger
 

Alan,

if you have already solved the transfer problem of received RAM-disk --> HDD then remains the broken tmp files. In one post you said to have a missed/incomplete HVS-2 files every 10 minutes. This is far too high for whatever reason (with your SNR of 16dB you should rather have one missed/incomplete file per day). Assuming these are OLCI EFR files of typically 700MB would mean you get 700MB more every 10 minutes that hang around for the next 3 hours.

This is in a nutshell what I found out: EUMETSAT can set a kind of timeout per product disseminated. This used to be 3 hours for OLCI EFR files but can be up to 24 hours for other low priority stuff according to KP. When you have missed (missed/unrecovered = lost) packets in the stream to that file it will hang around as incomplete tmp (actually full 700MB but with some 0 filled hole in it) and wait to be fixed. After the set timeout the client will delete a still incomplete tmp. It can be fixed by retransmissions within the set delay that EIP (Extremly Important Persons) can ask for (NACKs). Perhaps EUMETSAT also has a network of reference receivers so that they can detect widespread reception problems (maybe caused by their uplink) and initiate retransmission for those specific cases automatically. But the fact is most missed/incomplete files we get are caused by our local receiver problems EUMETSAT will never know about and will certainly not send some more extra packets for an amateur user in Cyprus or Sweden. That's why I asked EUMETSAT for the client switch I was talking about. With that switch every station that wants to use RAM-disks can decide whether the client should delete missed/incomplete files immediately. In this case you can forget tmp file management and just organize the RAM-disk ---> HDD transfer for fully received files. As a matter of fact, as the Windows client can even have tmp and received on different file systems (I don't recommend that), you could just have an unmanaged RAM-disk as a dynamic buffer for tmp files. More details in my two two papers inside the MVMSG 0.22 distribution that you will certainly understand.


Regards,
Ernst

P.S.
Just recently we suffered from sun satellite antenna colinearity (solar outage) that occurs twice a year.
This of course is a main RAM-disk filler event if broken HVS-2 tmp files are not deleted fast enough.

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