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PostPosted: Sun Jun 25, 2017 12:55 pm 
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Joined: Sun Jun 25, 2017 12:35 pm
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Hi all,

I've been using an external 5GB USB3 Expansion Desktop Drive from Seagate as a JBOD on my NSA-310. For some reason, once in a while the NSA would fail to recognise the USB drive and the USB led at the front would go red. The only way to recover was to power cycle the NSA.

So I went about purchasing an eSATA caddy, and using the drive via eSATA instead. I hoped that as it was the same drive, the NSA would just recognise it and mount the volume.

It has not... :-(

The drive is recognised, and I could create a JBOD or PC Compatible Volume, but I guess that even selecting a JBOD volume, it would simply create a new volume on it, possibly deleting the contents. I do not want to risk that as the drive contain data.

Is there any other way to get this volume added? I'm using FFP 0.7 on the NSA.

Thanks


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PostPosted: Sun Jun 25, 2017 1:01 pm 
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Joined: Sun Jun 25, 2017 12:35 pm
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Just to be clear, the device gets recognised by the NSA, but the existing volume does not get mounted automatically. The NSA does give me the opportunity to create a new eSATA volume on the external drive, but I don't wish to risk losing my data on it.

And I'm running this on it:

== Welcome at FFP version 0.7/arm, running on NSA310_ZyXEL nas, firmware V4.70(AFK.3) ==

Cheers


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PostPosted: Sun Jun 25, 2017 5:43 pm 
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Joined: Mon Jun 16, 2008 10:45 am
Posts: 6050
This is complicated. I'm not sure how an e-sata disk on a 310 should behave. All ZyXEL boxes treat external disks different from internal ones, and maybe an e-sata disk is treated as internal. You can create a raid array with an e-sata disk and an internal disk, AFAIK. But you can't using an USB disk. Not using the firmware.

fackie wrote:
an external 5GB USB3 Expansion Desktop Drive
I guess you mean 5TB? That *might* be a problem. A lot of the USB-sata controllers around expose 4k sectors for disks >2TiB. The reason is down compatibility with Windows XP. Using an MBR partition table (the only one supported by Windows XP) can only address 2^32 sectors. Using the default sector size of 512 bytes, this means you can't have a partition starting or ending beyond 2TiB. Using 4k sectors, this is stretched to 16TiB.
An e-sata interface can't do that, as there is nothing 'in between' the disk and the sata port.
*If* your USB-sata controller has such a function, the partition table is just not compatible with 512 byte sectors, and so the disk can't be mounted using e-sata.
You can see if that trick is used by connecting the disk by USB, and then execute (as root)
Code:
fdisk -l /dev/sdb
It will show a logical and a physical sector size. If the logical sector size is 4k, you can only use that disk over e-sata by re-partitioning it.


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PostPosted: Mon Jun 26, 2017 11:44 am 
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Joined: Sun Jun 25, 2017 12:35 pm
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Quote:
I guess you mean 5TB?


Doh! Of course! I did indeed mean 5TB - sorry about that.

Thanks for your explanation. Funny thing is, I already knew all that from years of experience in the field, yet didn't think of it at all... Thanks for the nudge.

So, you were absolutely correct. Mounted the drive back in the original USB enclosure and plugged it in:

root@nas:~# fdisk -l /dev/sdb1
Note: sector size is 4096 (not 512)

Disk /dev/sdb1: 5001.0 GB, 5000979808256 bytes
255 heads, 63 sectors/track, 76000 cylinders, total 1220942336 sectors
Units = sectors of 1 * 4096 = 4096 bytes
Sector size (logical/physical): 4096 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk identifier: 0x00000000

Disk /dev/sdb1 doesn't contain a valid partition table


It does of course contain a valid partition, because I can use it - just not from a firmware perspective, just like you said.

So I guess I'll have to park it for now until I find the alternative space to clear the drive and perhaps re-partition it in smaller chunks.

Also as an aside to potentially help others, the eSATA caddy also has a USB3 connection. I tried using it before reverting back into the old caddy, but that didn't seem to work. So one of three observations potentially apply here:

- The UUID of the drive would be different to the original and therefore the NSA310 would not automatically re-add it to the list
- The eSATA/USB3 caddy I've does not have the same sector translation abilities as the Seagate's own caddy
- The drive is just no recognised via USB in this caddy - I wasn't able to see it at all on NSA. Or perhaps a faulty caddy?

Cheers


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PostPosted: Mon Jun 26, 2017 4:19 pm 
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Joined: Mon Jun 16, 2008 10:45 am
Posts: 6050
fackie wrote:
perhaps re-partition it in smaller chunks.

That won't help you. The problem is not the size of the partition(s), it's the different sector size for the different interfaces.


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