usb devices disappear from /dev

[KingDuckZ]

Hello, I've built a lvm group with a few spare usb keys, made a LV and formatted it with ext4. The problem I have is that the devices making up my VG sometimes disappear from /dev or never appear at all. Sometimes, even after the LV is mounted and while I'm doing stuff on it, one of the usb keys goes missing or disconnects and pops back under a different /dev/sd* name.
In such cases lsusb would still show all the connected devices, but dmesg would show messages like:
device descriptor read/64, error -110.

I just had to reboot my raspberry, but I'll post more detailed messages as soon as the problem happens again. Can somebody help me with this please? Could it be a faulty usb key/hub? Other devices attached to my hub are working just fine.
$this->bbcode_second_pass_code('', '/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=dwc_otg/1p, 480M
|__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/3p, 480M
|__ Port 1: Dev 3, If 0, Class=Vendor Specific Class, Driver=smsc95xx, 480M
|__ Port 2: Dev 4, If 0, Class=Vendor Specific Class, Driver=rtl8192cu, 480M
|__ Port 3: Dev 5, If 0, Class=Hub, Driver=hub/7p, 480M
|__ Port 1: Dev 6, If 0, Class=Mass Storage, Driver=usb-storage, 480M
|__ Port 2: Dev 7, If 0, Class=Mass Storage, Driver=usb-storage, 480M
|__ Port 5: Dev 8, If 0, Class=Hub, Driver=hub/4p, 480M
|__ Port 1: Dev 10, If 0, Class=Mass Storage, Driver=usb-storage, 480M
|__ Port 2: Dev 11, If 0, Class=Mass Storage, Driver=usb-storage, 480M
|__ Port 3: Dev 12, If 0, Class=Mass Storage, Driver=usb-storage, 480M
|__ Port 4: Dev 13, If 0, Class=Hub, Driver=hub/1p, 480M
|__ Port 1: Dev 14, If 0, Class=Mass Storage, Driver=usb-storage, 480M
|__ Port 6: Dev 9, If 0, Class=Mass Storage, Driver=usb-storage, 480M')

Edit: So, quickly as expected, here is the problem:
$this->bbcode_second_pass_code('', '[root@alarmpi media]# vgscan
Reading all physical volumes. This may take a while...
/dev/vg_chiavona/lv_chiavona: read failed after 0 of 4096 at 57201852416: Errore di input/output
/dev/vg_chiavona/lv_chiavona: read failed after 0 of 4096 at 0: Errore di input/output
/dev/vg_chiavona/lv_chiavona: read failed after 0 of 4096 at 4096: Errore di input/output
Couldn't find device with uuid 2gCf39-wUeR-rfPA-iucp-7Yfw-jEFn-WL1tht.
Couldn't find device with uuid H7cQkI-hxwb-ZaEb-PzUv-Lvpl-cxEG-ehBva0.
Found volume group "vg_chiavona" using metadata type lvm2
[root@alarmpi media]# lsusb
Bus 001 Device 002: ID 0424:9512 Standard Microsystems Corp. LAN9500 Ethernet 10/100 Adapter
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 001 Device 016: ID 03f0:b107 Hewlett-Packard v255w/c310w Flash Drive
Bus 001 Device 017: ID 03f0:b107 Hewlett-Packard v255w/c310w Flash Drive
Bus 001 Device 018: ID 03f0:b107 Hewlett-Packard v255w/c310w Flash Drive
Bus 001 Device 019: ID 067b:2515 Prolific Technology, Inc. Flash Disk Embedded Hub
Bus 001 Device 003: ID 0424:ec00 Standard Microsystems Corp.
Bus 001 Device 004: ID 7392:7811 Edimax Technology Co., Ltd EW-7811Un 802.11n Wireless Adapter [Realtek RTL8188CUS]
Bus 001 Device 005: ID 050d:0307 Belkin Components USB 2.0 - 7 ports Hub [FSU307]
Bus 001 Device 006: ID 1058:1021 Western Digital Technologies, Inc. Elements 2TB
Bus 001 Device 007: ID 13fd:1340 Initio Corporation Hi-Speed USB to SATA Bridge
Bus 001 Device 015: ID 05e3:0608 Genesys Logic, Inc. USB-2.0 4-Port HUB
Bus 001 Device 009: ID 05dc:a017 Lexar Media, Inc.
Bus 001 Device 020: ID 067b:2517 Prolific Technology, Inc. Flash Disk Mass Storage Device
[root@alarmpi media]# lsusb -t
/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=dwc_otg/1p, 480M
|__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/3p, 480M
|__ Port 1: Dev 3, If 0, Class=Vendor Specific Class, Driver=smsc95xx, 480M
|__ Port 2: Dev 4, If 0, Class=Vendor Specific Class, Driver=rtl8192cu, 480M
|__ Port 3: Dev 5, If 0, Class=Hub, Driver=hub/7p, 480M
|__ Port 1: Dev 6, If 0, Class=Mass Storage, Driver=usb-storage, 480M
|__ Port 2: Dev 7, If 0, Class=Mass Storage, Driver=usb-storage, 480M
|__ Port 5: Dev 15, If 0, Class=Hub, Driver=hub/4p, 480M
|__ Port 1: Dev 16, If 0, Class=Mass Storage, Driver=usb-storage, 480M
|__ Port 2: Dev 17, If 0, Class=Mass Storage, Driver=usb-storage, 480M
|__ Port 3: Dev 18, If 0, Class=Mass Storage, Driver=usb-storage, 480M
|__ Port 4: Dev 19, If 0, Class=Hub, Driver=hub/1p, 480M
|__ Port 1: Dev 20, If 0, Class=Mass Storage, Driver=usb-storage, 480M
|__ Port 6: Dev 9, If 0, Class=Mass Storage, Driver=usb-storage, 480M')
From dmesg:
$this->bbcode_second_pass_code('', '[ 64.614265] NFSD: Using /var/lib/nfs/v4recovery as the NFSv4 state recovery directory
[ 64.850371] NFSD: starting 90-second grace period
[ 989.585868] EXT4-fs (dm-0): warning: mounting fs with errors, running e2fsck is recommended
[ 989.613156] EXT4-fs (dm-0): recovery complete
[ 989.619227] EXT4-fs (dm-0): mounted filesystem with ordered data mode. Opts: (null)
[ 1290.785725] EXT4-fs (dm-0): error count: 3
[ 1290.785759] EXT4-fs (dm-0): initial error at 1358858117: ext4_journal_start_sb:349
[ 1290.785782] EXT4-fs (dm-0): last error at 1358858152: ext4_put_super:859
[ 1697.619048] usb 1-1.3.5.1: reset high-speed USB device number 10 using dwc_otg
[ 1697.799087] usb 1-1.3.5.2: reset high-speed USB device number 11 using dwc_otg
[ 1698.048879] usb 1-1.3.5.1: reset high-speed USB device number 10 using dwc_otg
[ 1707.389508] usb 1-1.3.5.2: reset high-speed USB device number 11 using dwc_otg
[ 1707.569753] usb 1-1.3.5.1: reset high-speed USB device number 10 using dwc_otg
[ 1738.181890] usb 1-1.3.5.2: reset high-speed USB device number 11 using dwc_otg
[ 1739.182060] usb 1-1.3.5.1: reset high-speed USB device number 10 using dwc_otg
[ 1741.172164] usb 1-1.3.5.1: reset high-speed USB device number 10 using dwc_otg
[ 1772.184305] usb 1-1.3.5.1: reset high-speed USB device number 10 using dwc_otg
[ 1796.946424] usb 1-1.3.5.2: reset high-speed USB device number 11 using dwc_otg
[ 1827.228409] usb 1-1.3.5.2: reset high-speed USB device number 11 using dwc_otg
[ 1840.573217] hub 1-1.3.5:1.0: cannot reset port 2 (err = -71)
[ 1840.573573] hub 1-1.3.5:1.0: cannot reset port 2 (err = -71)
[ 1840.573816] hub 1-1.3.5:1.0: cannot reset port 2 (err = -71)
[ 1840.574073] hub 1-1.3.5:1.0: cannot reset port 2 (err = -71)
[ 1840.574317] hub 1-1.3.5:1.0: cannot reset port 2 (err = -71)
[ 1840.574340] hub 1-1.3.5:1.0: Cannot enable port 2. Maybe the USB cable is bad?
[ 1840.574571] hub 1-1.3.5:1.0: cannot disable port 2 (err = -71)
[ 1840.574835] hub 1-1.3.5:1.0: cannot reset port 2 (err = -71)
[ 1840.575070] hub 1-1.3.5:1.0: cannot reset port 2 (err = -71)
[ 1840.575317] hub 1-1.3.5:1.0: cannot reset port 2 (err = -71)
[...]
[ 1840.603953] hub 1-1.3.5.4:1.0: cannot reset port 1 (err = -71)
[ 1840.604260] hub 1-1.3.5.4:1.0: cannot reset port 1 (err = -71)
[ 1840.604536] hub 1-1.3.5:1.0: hub_port_status failed (err = -71)
[ 1840.604601] hub 1-1.3.5.4:1.0: cannot reset port 1 (err = -71)
[ 1840.604858] hub 1-1.3.5.4:1.0: cannot reset port 1 (err = -71)
[ 1840.604934] hub 1-1.3.5:1.0: hub_port_status failed (err = -71)
[ 1840.605231] hub 1-1.3.5.4:1.0: cannot reset port 1 (err = -71)
[ 1840.605257] hub 1-1.3.5.4:1.0: Cannot enable port 1. Maybe the USB cable is bad?
[ 1840.605333] hub 1-1.3.5:1.0: hub_port_status failed (err = -71)
[ 1840.605573] hub 1-1.3.5.4:1.0: cannot disable port 1 (err = -71)
[...]
[ 1840.620559] usb 1-1.3.5: USB disconnect, device number 8
[ 1840.620633] usb 1-1.3.5.1: USB disconnect, device number 10
[ 1840.629314] sd 3:0:0:0: [sdd] Unhandled error code
[ 1840.629351] sd 3:0:0:0: [sdd]
[ 1840.629364] Result: hostbyte=0x01 driverbyte=0x00
[ 1840.629380] sd 3:0:0:0: [sdd] CDB:
[ 1840.629406] cdb[0]=0x2a: 2a 00 00 01 31 08 00 00 08 00
[ 1840.629459] end_request: I/O error, dev sdd, sector 78088
[ 1840.629492] Buffer I/O error on device dm-0, logical block 9249
[ 1840.629506] lost page write due to I/O error on dm-0
[ 1840.629680] Buffer I/O error on device dm-0, logical block 67110
[...]
[ 1841.853306] usb 1-1.3.5.2: New USB device found, idVendor=03f0, idProduct=b107
[ 1841.853357] usb 1-1.3.5.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 1841.853414] usb 1-1.3.5.2: Product: USB FLASH DRIVE
[ 1841.853445] usb 1-1.3.5.2: Manufacturer: HP
[ 1841.853463] usb 1-1.3.5.2: SerialNumber: AA2B1C4A00000180
[ 1841.867875] scsi8 : usb-storage 1-1.3.5.2:1.0
[ 1841.950304] usb 1-1.3.5.3: new high-speed USB device number 18 using dwc_otg
[ 1842.058377] usb 1-1.3.5.3: New USB device found, idVendor=03f0, idProduct=b107
[ 1842.058451] usb 1-1.3.5.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 1842.058485] usb 1-1.3.5.3: Product: USB FLASH DRIVE
[ 1842.058503] usb 1-1.3.5.3: Manufacturer: HP
[ 1842.058519] usb 1-1.3.5.3: SerialNumber: AA2A171800000493
[ 1842.075554] scsi9 : usb-storage 1-1.3.5.3:1.0
[ 1842.150331] usb 1-1.3.5.4: new high-speed USB device number 19 using dwc_otg
[ 1842.264308] usb 1-1.3.5.4: New USB device found, idVendor=067b, idProduct=2515
[ 1842.264343] usb 1-1.3.5.4: New USB device strings: Mfr=1, Product=3, SerialNumber=0
[ 1842.264403] usb 1-1.3.5.4: Product: Eutron PicoDisk ProHS+ Hub
[ 1842.264423] usb 1-1.3.5.4: Manufacturer: Prolific Technology Inc.
[ 1842.265848] hub 1-1.3.5.4:1.0: USB hub found
[ 1842.266315] hub 1-1.3.5.4:1.0: 1 port detected
[ 1842.539619] usb 1-1.3.5.4.1: new high-speed USB device number 20 using dwc_otg
[ 1842.653536] usb 1-1.3.5.4.1: New USB device found, idVendor=067b, idProduct=2517
[ 1842.653587] usb 1-1.3.5.4.1: New USB device strings: Mfr=1, Product=4, SerialNumber=0
[ 1842.653607] usb 1-1.3.5.4.1: Product: USB Mass Storage Device
[ 1842.653624] usb 1-1.3.5.4.1: Manufacturer: Prolific Technology Inc.
[ 1842.664084] scsi10 : usb-storage 1-1.3.5.4.1:1.0
[ 1852.304141] scsi 9:0:0:0: Direct-Access hp USB Flash Drive 1638 PQ: 0 ANSI: 4
[ 1852.311522] sd 9:0:0:0: [sdh] 31950720 512-byte logical blocks: (16.3 GB/15.2 GiB)
[ 1852.312327] sd 9:0:0:0: [sdh] Write Protect is off
[ 1852.312380] sd 9:0:0:0: [sdh] Mode Sense: 43 00 00 00
[ 1852.313297] sd 9:0:0:0: [sdh] No Caching mode page present
[ 1852.313327] sd 9:0:0:0: [sdh] Assuming drive cache: write through
[ 1852.328896] sd 9:0:0:0: [sdh] No Caching mode page present
[ 1852.328933] sd 9:0:0:0: [sdh] Assuming drive cache: write through
[ 1852.330463] sdh: sdh1
[ 1852.335071] sd 9:0:0:0: [sdh] No Caching mode page present
[ 1852.335121] sd 9:0:0:0: [sdh] Assuming drive cache: write through
[ 1852.335145] sd 9:0:0:0: [sdh] Attached SCSI removable disk
[ 1852.672486] scsi 10:0:0:0: Direct-Access Eutron PicoDisk ProHS+ 1.00 PQ: 0 ANSI: 0 CCS
[ 1852.676630] sd 10:0:0:0: [sdi] 253952 512-byte logical blocks: (130 MB/124 MiB)
[ 1852.680276] sd 10:0:0:0: [sdi] Write Protect is off
[ 1852.680348] sd 10:0:0:0: [sdi] Mode Sense: 00 26 00 00
[ 1852.683727] sd 10:0:0:0: [sdi] No Caching mode page present
[ 1852.683762] sd 10:0:0:0: [sdi] Assuming drive cache: write through
[ 1852.697364] sd 10:0:0:0: [sdi] No Caching mode page present
[ 1852.697414] sd 10:0:0:0: [sdi] Assuming drive cache: write through
[ 1852.738058] sdi: sdi1
[ 1852.748713] sd 10:0:0:0: [sdi] No Caching mode page present
[ 1852.748890] sd 10:0:0:0: [sdi] Assuming drive cache: write through
[ 1852.748935] sd 10:0:0:0: [sdi] Attached SCSI removable disk
[ 1873.232044] usb 1-1.3.5.1: reset high-speed USB device number 16 using dwc_otg
[ 1873.412162] usb 1-1.3.5.2: reset high-speed USB device number 17 using dwc_otg
[ 1883.412790] usb 1-1.3.5.1: reset high-speed USB device number 16 using dwc_otg
[ 1883.592828] usb 1-1.3.5.2: reset high-speed USB device number 17 using dwc_otg
[ 1899.594155] usb 1-1.3.5.1: reset high-speed USB device number 16 using dwc_otg
[ 1899.774027] usb 1-1.3.5.2: reset high-speed USB device number 17 using dwc_otg
[ 1899.954157] usb 1-1.3.5.1: reset high-speed USB device number 16 using dwc_otg
[ 1900.134227] usb 1-1.3.5.2: reset high-speed USB device number 17 using dwc_otg
[ 1910.135009] usb 1-1.3.5.1: reset high-speed USB device number 16 using dwc_otg
[ 1910.236429] scsi 7:0:0:0: Device offlined - not ready after error recovery
[ 1910.315035] usb 1-1.3.5.2: reset high-speed USB device number 17 using dwc_otg
[ 1910.415965] scsi 8:0:0:0: Device offlined - not ready after error recovery')

Last, ls:
$this->bbcode_second_pass_code('', '[root@alarmpi media]# ls -1 /dev/sd*
/dev/sda
/dev/sda1
/dev/sdb
/dev/sdb1
/dev/sdc
/dev/sdc1
/dev/sdh
/dev/sdh1
/dev/sdi
/dev/sdi1')
Why does it keep on happening?? My kernel version: 3.6.11-3-ARCH+

[pepedog]

USB problems on the raspberry pi used to be worse than this
Might be best to look thru this
https://github.com/raspberrypi/linux/issues

[KingDuckZ]

So uhm... it's a power problem? I'm using one of these, which shows a green led for every connected port. Sometimes when connecting a usb key (or more often, another hub) all the leds go blank for half a second and then turn green again. Of course that wreaks havok to any mounted device. I thought the raspberry was responsible for that, not the power supply. My raspberry is connected to the wall socket directly through a dedicated plug. The usb hub has its own power plug, so I suppose usb keys get powered from there. :/

[KingDuckZ]

I attached two smaller hubs to the main usb hub, and only connected two usb keys to each. This has somewhat mitigated the problem, but I still "lose" a device occasionally. I'm waiting for a new usb hub, hopefully it will help fixing the problem.

Besides, I have the problem that even when all devices are detected the LV is shown as inactive after reboot. I enabled lvm.service already, and the only way to activate my LV is to either issue the vgchange command manually or restart lvm.service (just starting won't do anything). Any help please? Should I start a new thread? (Edit: I suspect my usb devices only appear after lvm.service is started).