Re: Question: raid1 behaviour on failure

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On Thu, Apr 28, 2016 at 7:09 AM, Matthias Bodenbinder
<matthias@xxxxxxxxxxxxxx> wrote:
> Am 26.04.2016 um 18:19 schrieb Henk Slager:
>> It looks like a JMS567 + SATA port multipliers behaind it are used in
>> this drivebay. The command   lsusb -v  could show that. So your HW
>> setup is like JBOD, not RAID.
>
> Here is the output of lsusb -v:
>
>
> Bus 003 Device 004: ID 152d:0567 JMicron Technology Corp. / JMicron USA Technology Corp.
> Device Descriptor:
>   bLength                18
>   bDescriptorType         1
>   bcdUSB               3.00
>   bDeviceClass            0 (Defined at Interface level)
>   bDeviceSubClass         0
>   bDeviceProtocol         0
>   bMaxPacketSize0         9
>   idVendor           0x152d JMicron Technology Corp. / JMicron USA Technology Corp.
>   idProduct          0x0567
>   bcdDevice            2.05
>   iManufacturer          10 JMicron
>   iProduct               11 USB to ATA/ATAPI Bridge
>   iSerial                 5 152D00539000
>   bNumConfigurations      1

OK, that is how the drivebay presents itself. It does not really
correspond to this:
http://www.jmicron.com/PDF/brief/jms567.pdf
It looks more like a jms562 is used, but I don't know what is on the
PCB and in the FW

Anyhow, hot (un)plug capability on the 4 internal SATA i/f is not
explicitly mentioned. If you expect or want that, ask Fantec I would
say.

>   Configuration Descriptor:
>     bLength                 9
>     bDescriptorType         2
>     wTotalLength           44
>     bNumInterfaces          1
>     bConfigurationValue     1
>     iConfiguration          0
>     bmAttributes         0xc0
>       Self Powered
>     MaxPower                2mA
>     Interface Descriptor:
>       bLength                 9
>       bDescriptorType         4
>       bInterfaceNumber        0
>       bAlternateSetting       0
>       bNumEndpoints           2
>       bInterfaceClass         8 Mass Storage
>       bInterfaceSubClass      6 SCSI
>       bInterfaceProtocol     80 Bulk-Only
>       iInterface              0
>       Endpoint Descriptor:
>         bLength                 7
>         bDescriptorType         5
>         bEndpointAddress     0x81  EP 1 IN
>         bmAttributes            2
>           Transfer Type            Bulk
>           Synch Type               None
>           Usage Type               Data
>         wMaxPacketSize     0x0400  1x 1024 bytes
>         bInterval               0
>         bMaxBurst              15
>       Endpoint Descriptor:
>         bLength                 7
>         bDescriptorType         5
>         bEndpointAddress     0x02  EP 2 OUT
>         bmAttributes            2
>           Transfer Type            Bulk
>           Synch Type               None
>           Usage Type               Data
>         wMaxPacketSize     0x0400  1x 1024 bytes
>         bInterval               0
>         bMaxBurst              15
> Binary Object Store Descriptor:
>   bLength                 5
>   bDescriptorType        15
>   wTotalLength           22
>   bNumDeviceCaps          2
>   USB 2.0 Extension Device Capability:
>     bLength                 7
>     bDescriptorType        16
>     bDevCapabilityType      2
>     bmAttributes   0x00000002
>       Link Power Management (LPM) Supported
>   SuperSpeed USB Device Capability:
>     bLength                10
>     bDescriptorType        16
>     bDevCapabilityType      3
>     bmAttributes         0x00
>     wSpeedsSupported   0x000e
>       Device can operate at Full Speed (12Mbps)
>       Device can operate at High Speed (480Mbps)
>       Device can operate at SuperSpeed (5Gbps)
>     bFunctionalitySupport   1
>       Lowest fully-functional device speed is Full Speed (12Mbps)
>     bU1DevExitLat          10 micro seconds
>     bU2DevExitLat        2047 micro seconds
> Device Status:     0x0001
>   Self Powered
>
>
>
>> IMHO, using such a setup for software RAID (like btrfs RAID1)
>> fundamentally violates the concept of RAID (redundant array of
>> independent disks). It depends on where you define the system border
>> of the (independent) disks.
>> If it is at:
>>
>> A) the 4 (or 3 disk in this case) SATA+power interfaces inside the drivebay or
>>
>> B) inside the PC's chipset.
>>
>> In case A) there is a shared removable link (USB) inside the
>> filesystem processing machine.
>> In case B) the disks aren't really independent as they share a
>> removable link (and as proven by the (un)plug of 1 device affecting
>> all others).
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>
>
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