Re: Gaps in AVHRR images yesterday.

David J Taylor GM8ARV 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🇪🇺


Thanks for pointing me (again) to TD 15.
It really is now quite comprehensive.

And I still have my 999 MB RAMdisk unused which I was going to (will) experiment with.
As you know Ops want me to do a couple of tests on my current setup which I'll do hopefully under clear sky conditions - when they return.

I've also thought of having a second HDD for HVS-1 alone.

[I have an SSD for 'Windows.']

TD 15 also recommends RAMdisk - and interestingly - SSD's which you used not to favour(?) as it points out HDD's are 'slow' in these days of high data level I/O's..
And, Ernst has pointed out that the new generation of HDD's are 'slower' and best avoided.

So I have a couple of updates to consider to 'speed things up?'



I am not completely happy with SSDs for EUMETCast data because they have a limited number of write cycles, a limited total data throughput, resulting in a limited lifetime. Perhaps with today's SSDs these limits are such that it's an acceptable choice,and if the user is aware of that, fine. Remember that there's not only receiving the data, but there might be processing as well. For HVS-2 it's something like 450 GB per day from the source.

HDD - slow
SSD - fast
RAMdisk - much faster

But RAMdisk is limited in capacity and may need more management. Some of my systems are now using RAMdisk (1-2 GB for BAS, 10 GB for HVS-2 [receive-only]) with Robocopy moving the data from the RAMdisk onto HDD once a minute, and with TrimTree running regularly to remove any lingering "tmp" files. One HVS-1 system writes directly to a separate HD, One BAS system works well without any RAMdisk.

It's other things which can help too - preventing any unwanted disk access from e.g. indexing and anti-virus. Minimising the data you take.

One thing which I'm increasingly finding critical is to maximise the number of data paths through the system. Perhaps add a second HDD controller rather than just another SATA connection. I'm currently thinking about adding a second USB internal hub for the TBS5925 as the PC has a single master hub. There's an element of "try it and see" about this level of changes.

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Email: david-taylor@...
Twitter: @gm8arv

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