Re: RAID-1 and Reiser4 issue: umount hangs

[Arend Freije <afreije@inn.nl>]

Alexander Zarochentsev wrote:
> On Tuesday 30 May 2006 23:20, Arend Freije wrote:
>   
>> Alexander Zarochentsev wrote:
>>     
>>> Hello,
>>>
>>> On Tuesday 30 May 2006 00:17, Arend Freije wrote:
>>>       
>>>> Hi,
>>>>
>>>> I'm using Reiser4 for my filesystems on disk (/dev/sda) , and it
>>>> works just fine. Recently I bought a second disk (/dev/sdb) for
>>>> RAID-1 mirroring. With mdadm I created a degraded raid-1 array  on
>>>> /dev/md/0, devices missing,/dev/sdb1. After that I created a
>>>> Reiser4 filesystem on /dev/md/0 and mounted it at /mnt. Then I
>>>> copied the data from /dev/sda1 to /mnt.
>>>>         
>>> would it work better with "no_write_barrier" mount option?
>>>       
>> It would indeed. What's the purpose of this option?
>>     
>
> It disables write barrier support in reiser4 which may be buggy.  It is 
> not necessary that reiser4 code has a bug, but the elevator, md device 
> or disk driver code.
>   
Alexander,

You're probably right. I found several posts on the linux-kernel list
involving problems with write barrier support in combination with SATA
and ext3 . So I tried:

# mkfs -t ext3 /dev/md/0
# mount -o barrier=1 /dev/md/0 /mnt
# cp -a $src /mnt
# umount /mnt

And indeed, umount hangs now as well.
So it seems to be a linux-kernel issue after all...

If write-barrier support is a known problem, wouldn't it be better to
disable it in the Reiser4 driver by default, as in the ext3-driver ?

Kind Regards,

Arend Freije