25 replies to this topic

[WanWizard]

You should not use an AV disk in an STB, but a regular disk.

 

AV disks have firmware optimized for CCTV recording which favours sequential writes and high throughput over data consistency, in other words it accepts data loss. That is not a requirement for an STB. An average 5400rpm laptop disk is plenty fast enough for all the recordings you plan to make, so save yourself some money on this point...

[nisseH]

With an ordinary HDD: when a data fault, the hdd expects that a new package instead of the faulty one will be sent.

The probelem with that is that it will not come a new package and because of that the hdd will wait a "long" time which can result in a "big" glitch in the picture.

An AV hdd don't wait for a new package and therefore will not wait and continue as nothing have happend, no wait time, and the glitch much less if you even will notice it.

This problem may not happend often for a normal user.

 

I record more than 4-10 programs evry day, It's not unusual that I have 4 or more recordings at the same time, for several hours, so for me there is a diffrence.

[littlesat]

I’m afraid wanwizard is right....

[WanWizard]

I do the same (Duo 4K with 2 FBC modules, so 16 tuners), with a bog-standard 2,5" 1500GB laptop disk. Which has been running for years.

 

You're disucssing a theoretical situation that will simply never happen, but hey, it's your money.

[anudanan]

The main problem with the current 2,5 inch HDDs is the use of the SMR recording instead of using the classic CMR recroding technology. Sometimes a SMR HDD are very slow during write requests in particular if the are many parallel recordings running or in parallel some other actions are on the HDD.

 

I´ve made many tests with a classic CMR HDD and a modern SMR HDD.

A SMR HDD is not a good working HDD and is not usefull for the realtime requirement of the recordings. For an archive HDD the SMR ist ok.

 

Today most current 2,5 inch HDDs with 2TB or more use the SMR technology and that is very bad.

 

I have  made many tests in the past with a ST2000LM0t5 or ST2000LX001 2TB HDD in my two uno4kse and these HDDs are not suitable for a STB which can make many parallel recordings and which has a powerful CPU to do a copy or movie cut in parallel to the recordings. With a SMR HDD it doesn´t work without hicks in the recorrdings, but with a classic HDD (ST2000LM003) it works very perfectly.

 

Sometime the SMR HDD musts make many internal additional track reads and writes for writing a new track betweeing existing data tracks. The tracks are overlapping in SMR HDD and that is the disadvantage of the SMR HDD. They are not able to write a single track between neighbour tracks as a classic CMR HDD can do

 

A SMR HDD normally has 128MB and more internal cache to handle the additional internal reads and writes  So if a HDD has so much cache it maybe a SMR HDD.

Edited by anudanan, 13 August 2019 - 06:59.

[twol]

DUO4K is faster than Ultimo4K and have probably a better cpu than Ultimo4K.


The first problem is DUO4K and the hdd and this problem could be that decide which box I buy.
I can't find any company that sells any AV hdd bigger than 1TB The only 2.5" AV hdd's that I could find is WD AV-25 WD10JUCT 16MB 1TiB and HGST Cinemastar 5K1000 HCC541010B9E360 16MB 1TB


It seems that Ultimo4K is better if I want to be able to use a 3.5" hdd and more than 2TB. Then I would by a WD Purple NV 4TB Surveillance Hard Disk Drive, WD4NPURX , 3.5"

There are maybee a solution in how to use a 3.5" hdd with DUO4K but I don't know if it's possible in a simple way.

If it is possible to connect the hdd to the DUO4K as I have done with my Dreambox 8000 then DUO4K could be the one.
I have the 3.5" hdd outside my Dreambox 8000, but it 's connected to the SATA and power connections inside the box.
The hdd is in a "4-in-3" hdd case with a 120mm fan. I have done this so that the hdd always will be cold and this also makes the box temp lower.
Dreambox have it's power supply inside the box and it can get very varm so the above solution solved that problem.

Is it possible to take away the DUO4K's hdd bay and connect sata + power cables so that I can have the hdd as an "external" drive?
Anyway it have been better if VU+ have released an upgraded Ultimo4K box.


The second "problem": Which LNB should I buy?

It must be very good one that will work even if it's snowing very much (in the winter) or when it's raining very much. That shouldn't be a problem, but next could be.
I hope that there is one that have 4 old type of lnb connectors + 1 Single Cable connector that have more than 24 channels,
if not I have one, with 2 old type lnb connectors + 1 single cable connector with 24 channels but I'm not shure if it can handle both types together at the same time.

Rain/Snow .... buy a hood for the LNB - works well (or make your own from a plastic container) - only issue is that after a few years depending on the plastic you have to replace due to the sunshine destroying it.

External drive - Gigablue Quad 4K has esata connection

Edited by twol, 13 August 2019 - 07:23.

[WanWizard]

I have  made many tests in the past with a ST2000LM0t5 or ST2000LX001 2TB HDD in my two uno4kse and these HDDs are not suitable for a STB which can make many parallel recordings and which has a powerful CPU to do a copy or movie cut in parallel to the recordings. With a SMR HDD it doesn´t work without hicks in the recorrdings, but with a classic HDD (ST2000LM003) it works very perfectly.

 

Quite possible, I never said that all disks are ok.

 

I use an ST1500LM connected to my Duo 4K (via USB2), and it has none of the issues you descriibe, I've never seen a hickup in a recording.

[anudanan]

The two ST1500LM models from seagate are HDDs with the classic CMR recording technology. They don´t have the typical SMR problems

[WanWizard]

Ok. So the statement can be revised to "Any HDD not using SMR technology will do". In general that means "most non-Seagate disks will be fine".

 

BTW, also avoid those Seagate Hybrid drives, HDD with SSD cache. The HDD is SMR too, and the SSD doesn't do a bit to help. I've got one in my laptop at the moment, I/O wise it's a disaster, it's slow and under heavy I/O processes freeze waiting for I/O.

[anudanan]

Many WD HDDs also use SMR and many versions of the L200 Toshiba HDDs use also SMR

[nisseH]

Many WD HDDs also use SMR and many versions of the L200 Toshiba HDDs use also SMR

 

How do I know if a hdd uses SMR or CMR recording? I can't find any information about that in the datasheet. 

[WanWizard]

They are very good at hiding it. One of the clues you can look for is buffer size.

 

SMR drives have very high buffers (like 128MB) to deal with the poor write performance, which PMR drives don't need that and have typical 4-16MB buffers.

[anudanan]

That is a very poor information strategie of all HDD manufactors to say nothing about SMR and many users don‘t about the poor write performance. Instead of that they advertise the big cache size.

That is very poor and 0 percent customer orientet.

[nisseH]

And I thought that a bigger cache was better. The WD Purple NV 4TB Surveillance Hard Disk Drive, WD4NPURX , 3.5"  have 64MB cache but does it use CMR?.   But an AV hdd should use CMR or?

Do you have a list of hdd's that use CMR recording?

[WanWizard]

Afaik, the current WD Purple series is still CMR.

 

Other that spend quite a bit of time on Google, I haven't found a way to determine whether or not a disk is using SMR.

 

If I'd known, I wouldn't have bought this crap Seagate FireCuda...

[betacentauri]

Yes, it’s a shame that most new hdds use SMR.

Here you can search/filter:
https://geizhals.de/?cat=hde7s
But I think not everything is correct.
And yes, the buffer size is a good indicator.

[WanWizard]

That goes in my bookmarks!

 

And it confirms the 2,5" FireCuda's are SMR disks, which explains the dreadful performance under I/O. Time for a new disk.

[twol]

It would be worth selectively editing this post and using it as a HDD selection sticky - with my background I thought I knew most things about disks - but shows how quickly you can miss something and be out of date.
Really useful information that makes you think hard.

[anudanan]

It would be a good idea to shift the HDD discussion in an extra new thead, if a mod will do this.

[Tech]

It would be a good idea to shift the HDD discussion in an extra new thead, if a mod will do this.

Good suggestion,..... done