Using multiple USB hard disks for extra capacity

[iogikuma]

I would like to connect two or more USB hard disks to my V2. They are standard external USB Seagate 2.5" hard disks of 4 and 5 terabyte capacity.
I have tried connecting my 2 USB hard disks through a USB3 powered hub on the standard hard disk USB port but then the V2 hangs on boot. I suspect that the port is USB2.
If I connect the USB3 hub via the USB port marked USB3 where the dongle tuner normally plugs in, I have to plug the USB tuner into the hub and it does not work, so I lose my extra tuners.
Can anybody advise how I can successfully connect my two hard disks simultaneously using a powered USB2 or USB3 hub?
At this stage, the only successful way to change hard disks is to switch off the V2, unplug the USB cable of the hard disk that is currently connected, plug in the other hard disk, then reboot the V2.
Another problem is that any scheduled recordings end up on the hard disk that is currently connected. So switching hard disks means that recordings end up on both hard disks which makes it hard to track what is where.
And if I can plug in more than one hard disk, how do I control on which disk the scheduled recordings get saved?

[MrQuade]

It sounds like you need a more powerful hub to supply all of those devices at once. Either that or make sure the hard-disks have their own independent supply.

Have you checked to see what happens if you plug the same things (hub, hard-disks and tuner) in to your PC? So they work there in the same connection arrangement?


The V2 will assign device ID's to the disks in whatever order it wants, which means, if you change the ports that the drives plug into, then the V2 may bring them online in a different order and your recordings location will change.

[Grumpy_Geoff]

And if I can plug in more than one hard disk, how do I control on which disk the scheduled recordings get saved?

With a V2 I think that you're asking for trouble if you boot with more than one USB storage device attached. The mount order may change from one boot to the next.

Transient attachments however should be okay.

"If you have more than one locally attached mass storage device, then it is unpredictable as to where it will be mounted."
viewtopic.php?f=66&t=13725&p=182830#p182830

[Grumpy_Geoff]

Have you checked to see what happens if you plug the same things (hub, hard-disks and tuner) in to your PC? So they work there in the same connection arrangement?

Won't the default ext4 format kibosh that (assuming Windows PC)?

The V2 will assign device ID's to the disks in whatever order it wants, which means, if you change the ports that the drives plug into, then the V2 may bring them online in a different order and your recordings location will change.

I don't think that changing ports specifically is required, sometimes just a reboot is sufficient. But true, swapping between a USB2 and USB3 port would probably do it (as prl has posted elsewhere of the port attachment order). What happens with multiple storages devices in a hub is anyone's guess, I guess.

If I had a V2, with multiple USB storage devices, I'd probably assign the primary recording device to the USB2 port (so mounted as /media/hdd or /media/usb if a micro SD card was also inserted). I'd then have a powered hub attached to the USB3 port, with the other HDD drives, tuner(s), wireless adapter connected. Then daily/weekly, depending on prevailing winds and celestial mechanics, sacrifice a few goats and hope all device mounts remain stable.
Otherwise, if network connected, I'd buy a NAS and record to it instead. Should be far more relaible.

[said by a bloke who doesn't have a V2 but has read a lot of the forum]

[MrQuade]

Won't the default ext4 format kibosh that (assuming Windows PC)?

They might not be able to see anything, but the drive should still be visible.

Otherwise, if network connected, I'd buy a NAS and record to it instead. Should be far more relaible.

I agree, that having multiple drives connected to the V2 is not ideal, and if you need dozens of TB of storage, then some sort of alternate arrangement would be preferable.

[prl]

I don't think that changing ports specifically is required, sometimes just a reboot is sufficient. But true, swapping between a USB2 and USB3 port would probably do it (as prl has posted elsewhere of the port attachment order). What happens with multiple storages devices in a hub is anyone's guess, I guess.

On the V2, I think the port scan order is microSD, USB2, USB3. The response and attachment order from devices attached directly or through a hub, will depend on how the firmware iterates over the hub tree and how quickly the devices respond, and thow quickly the devices partition map is scanned.

I think that's the reason why peteru thinks that the device name and mount order can never be completely relied on.

That said, when I have single-partition USB storage devices directly connected to both the USB2 and USB3 ports at boot time, the USB2 device has always been detected as /dev/sdb1 and the USB3 device as /dev/sdc1. But it;'s a situation I try to avoid, because it means that the (typically) USB thumb drive on the USB2 port gets mounted as /media/hdd

[Brainz]

I have tried connecting my 2 USB hard disks through a USB3 powered hub on the standard hard disk USB port but then the V2 hangs on boot. I suspect that the port is USB2.
If I connect the USB3 hub via the USB port marked USB3 where the dongle tuner normally plugs in, I have to plug the USB tuner into the hub and it does not work, so I lose my extra tuners.

I don't own a V2 but I am fairly sure the USB3 port is a correct option for HDDs leaving the USB2 port for the tuner dongle. I would connect the hub to USB3 to power the drives and leave the dongle in the USB2 port. If you are not using Wifi that should be all you need.

[prl]

I don't own a V2 but I am fairly sure the USB3 port is a correct option for HDDs leaving the USB2 port for the tuner dongle. I would connect the hub to USB3 to power the drives and leave the dongle in the USB2 port. If you are not using Wifi that should be all you need.

I think that "correct" isn't quite the term I'd use.

• The USB3 port can provide more current (1000mA) than the USB2 port (500mA). Some portable HDDs that are powered from USB require more than 500mA (900mA isn't unusual). They will work on the USB3 port but not on the USB2 port. The Toshiba Canvio Basica 1TB drive I have on my test V2 will work just fine on both. It's unusual to find the USB current requirements in HDD specs these days, so you can often only find out by experimentation.
• The USB3 port can support a total of 1000mA current out. If you use a USB-powered hub, you'll be unlikely to be able to attach more than one HDD to it. To do so, you'd need the total current needs of the HDDs to sum to less than 900mA (since the hub will typically demand 100mA for its own purposes, and many HDDs need 500mA or more. See here in another similar discussion for an example of how quickly a USB-powered hub's current budget can evaporate.
• The USB3.0 port can provide more data throughput (nominal 5Gb/s) than the USB2 port (nominal 480Mb/s), though both can easily handle typical record/playback disk I/O traffic. However, it makes sense to put more bandwidth-demanding devices on the USB3 port: so HDD(s) on USB3 and WiFi dongle or USB tuner on USB2. Or, if you use a hub, you could put everything that's "permanently" connected on the hub, and leave the USB2 port free for firmware updates and USB drive file transfer (but note the next dot point)
• In a simple setup with only a USB HDD connected for recording & timeshift, if the USB HDD is connected to the USB3 port, and a USB thumb drive is connected to the USB2 port, and the V2 is restarted, the thumb drive is likely to be mounted as /media/hdd, and recordings and timeshift will be directed to it. If the HDD is connected to the USB2 port and a USB thumb drive is connected to the USB3 port and the PVR is restarted, then the two devices will normally be attached as expected, with the HDD mounted as /media/hdd and the thumb drive as /media/usb.

The vagaries of USB HDD attachment, especially in more complicated setups with multiple HDD mounts through hubs, are one of my least favourite things about the V2, and make it, except in the simplest of setups, a bit of a challenge even for reasonably technically knowledgeable people.

Throwing a microSD card into the mix just adds to the HDD attachment naming issues.

[peteru]

I think that's the reason why peteru thinks that the device name and mount order can never be completely relied on.

From a software design point of view, the current enumeration mechanisms are not guaranteed to result in a behaviour that can be considered consistent and predictable. Most of my contributions to these discussions in the past have been take from a point of view that looks for a workable and robust solution. The tricky part is covering all the edge cases, including the fact that with the V2 mostly using external media, devices are likely to come and go and use a variety of partitioning schemes and file systems.

The empirical observations that users may have are very likely to include many scenarios where one particular configuration and sequence always results in the same enumeration. That is great and possibly quite workable for specific cases. For now, it's probably the best "solution" available. However, it is not the generic software solution that I would like to see implemented.

Returning back to the original poster... Multiple HDDs should work without any issues as long as you supply enough power to each device, including the hub.