Re: Failed reads from RAID-0 array (from newbie who has read the FAQ)
Neil:
Relevant stack trace follows. Any suggestions? blk_backing_dev_unplug...
Does that mean the raid subsystem thinks one of the usb drives has been
removed? I assure you that physically this is untrue, but that doesn't
mean that some sort logical disconnect hasn't happened...
Makes me wonder if one of my USB hub connections is intermittent...
I would also welcome any tips on any other developers group to follow up
with. I haven't hacked any kernel code since the 2.2.x kernel and things
have changed a bit! I don't mind digging into this, but I suspect I could
get things cleared up fast if I could find the right subject expert!
===
cpD E2FBEDB0 1784 4271 4270 (NOTLB)
e2fbedb4 00200086 c15dc550 e2fbedb0 0001 00200082 1000
c15dc550 000a e94182b0 f3161430 26320f40 01c5
e94183bc c1c8c480 ecd7d300 c04e0bf2 c042e0e4 f7d767f8
003b6622
Call Trace:
[] blk_backing_dev_unplug+0x73/0x7b
[] getnstimeofday+0x30/0xb6
[] io_schedule+0x3a/0x5c
[] sync_page+0x0/0x3b
[] sync_page+0x38/0x3b
[] __wait_on_bit_lock+0x2a/0x52
[] __lock_page+0x58/0x5e
[] wake_bit_function+0x0/0x3c
[] do_generic_mapping_read+0x1e0/0x459
[] generic_file_aio_read+0x173/0x1a6
[] file_read_actor+0x0/0xe0
[] do_sync_read+0xc7/0x10a
[] autoremove_wake_function+0x0/0x35
[] do_sync_read+0x0/0x10a
[] vfs_read+0xa6/0x152
[] sys_read+0x41/0x67
[] syscall_call+0x7/0xb
===
--
Michael Schwarz
> My guess would be a locking bug in the usb storage driver or some
> lower level USB driver..
> A significant difference between raid0 and linear is that a largish IO
> will touch all drives for raid-0, but only one or two for linear.
> That gives much more opportunity for locking bugs to hit.
>
> When it is in the hanging state, do
> echo t > /proc/sysrq-trigger
>
> and look in the kernel logs for the stack trace of all processes.
> Hopefully the stack trace for the processes in 'D' state will be
> informative.
>
> NeilBrown
>
>
>>
>> Here are my mdadm commands to create the array:
>>
>> mdadm --create /dev/md0 --level=linear --auto=md --chunk=32
>> --raid-devices=7 /dev/sd?
>>
>> (The wildcard works because the seven flash drives are the only scsi
>> devices on the system).
>>
>> The command for the raid-0 array is the same as above except for the
>> "--level=0" it takes to make a raid 0 array.
>>
>> I then use "mkfs" to make the filesystem and mount the resulting array
>> at
>> "/mnt"
>>
>> Can anyone give a raid newbiw some tips? Is there something obvious I'm
>> missing? Would it help to provide strace/ltrace/ptrace of the hanging
>> copy
>> command?
>>
>> Any help (including URLs of manuals I should RTFM) would be most
>> welcome.
>>
>> Thanks!
>>
>>
>> --
>> Michael Schwarz
>>
>>
>> -
>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>> the body of a message to [EMAIL PROTECTED]
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>
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Re: Failed reads from RAID-0 array (from newbie who has read the FAQ)
On Friday March 16, [EMAIL PROTECTED] wrote: > I'm not a Linux newbie (I've even written a couple of books and done some > very light device driver work), but I'm completely new to the software > raid subsystem. > > I'm doing something rather oddball. I'm making an array of USB flash > drives and comparing read and write rates. > > Well, I've had great success writing. I've got seven flash drives on a > hub. I've joined them up both linear and raid0 and written large amounts > of data to them. But come time to read from them, linear works, but raid0 > hangs after transferring just shy of 2G of data. It doesn't matter if it > reading from one file or from many files whose cumulative size is just shy > of 2G. It doesn't matter if I'm using "dd" or "cp" to read the file or > files. > > The process doing the transfer is unkillable. Not with a kill -15 or a > kill -9. It won't die, but it also won't make progress. > > "Linear" always works. Raid-0 always hangs. My guess would be a locking bug in the usb storage driver or some lower level USB driver.. A significant difference between raid0 and linear is that a largish IO will touch all drives for raid-0, but only one or two for linear. That gives much more opportunity for locking bugs to hit. When it is in the hanging state, do echo t > /proc/sysrq-trigger and look in the kernel logs for the stack trace of all processes. Hopefully the stack trace for the processes in 'D' state will be informative. NeilBrown > > Here are my mdadm commands to create the array: > > mdadm --create /dev/md0 --level=linear --auto=md --chunk=32 > --raid-devices=7 /dev/sd? > > (The wildcard works because the seven flash drives are the only scsi > devices on the system). > > The command for the raid-0 array is the same as above except for the > "--level=0" it takes to make a raid 0 array. > > I then use "mkfs" to make the filesystem and mount the resulting array at > "/mnt" > > Can anyone give a raid newbiw some tips? Is there something obvious I'm > missing? Would it help to provide strace/ltrace/ptrace of the hanging copy > command? > > Any help (including URLs of manuals I should RTFM) would be most welcome. > > Thanks! > > > -- > Michael Schwarz > > > - > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to [EMAIL PROTECTED] > More majordomo info at http://vger.kernel.org/majordomo-info.html - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
