Is that normal a removed part in RAID0 still showed as "active sync"

Is that normal a removed part in RAID0 still showed as "active sync"

[Hxsrmeng]

The /dev/md0 is set as RAID0
"cat /proc/mdstat" shows
md0 : active raid0 sda1[0] sdd1[3] sdc1[2] sdb1[1]
157307904 blocks 64k chunks

Then sdd is removed.

But  "cat /proc/mdsta" still shows the same information as above, while two
RAID5 devices show their sdd parts as (F)
md0 : active raid0 sda1[0] sdd1[3] sdc1[2] sdb1[1]
157307904 blocks 64k chunks

Is this normal?

Also, when using "mdadm --detail"
sdd1( part of RAID0) is showed as "active sync", but sdd2(which is part of
RAID5) is showed as "removed"

Thank you.

-- 
View this message in context: http://www.nabble.com/Is-that-normal-a-removed-part-in-RAID0-still-showed-as-%22active-sync%22-tp14670113p14670113.html
Sent from the linux-raid mailing list archive at Nabble.com.

Re: Is that normal a removed part in RAID0 still showed as "active sync"

[Neil Brown]

On Monday January 7, hxsrmeng@gmail.com wrote:
> 
> The /dev/md0 is set as RAID0
> "cat /proc/mdstat" shows
> md0 : active raid0 sda1[0] sdd1[3] sdc1[2] sdb1[1]
> 157307904 blocks 64k chunks
> 
> Then sdd is removed.
> 
> But  "cat /proc/mdsta" still shows the same information as above, while two
> RAID5 devices show their sdd parts as (F)
> md0 : active raid0 sda1[0] sdd1[3] sdc1[2] sdb1[1]
> 157307904 blocks 64k chunks
> 
> Is this normal?

Yes.

raid0 is not real raid.  It is not able to cope with disk failures, so
it doesn't even try.  Devices in a raid0 are never marked failed as
doing so would be of no benefit.

NeilBrown

Re: Is that normal a removed part in RAID0 still showed as "active sync"

[hxsrmeng]

Thanks. That's really helpful.

When doing this, I used "tail -f /var/log/messages" to monitor my
program, which does I/O to md0.

After sdd was removed physically, it seemed the I/O operations to the
md0 continued: 
"tail -f /var/log/messages" occasionally shows:
     SCSI error: return code = 0x00040000
     kernel: end_request: I/O error, dev sdd, sector 15357599
but showed all the other messages just as sdd was still there.

Is this normal? 

I am really not sure whether the result of my program is still
trustable.

Also, if sdd1 is the only device which fails, is there any way to know
it? Just as what "mdadm --monitor" does?

Thank you.


On Tue, 2008-01-08 at 14:53 +1100, Neil Brown wrote:
> On Monday January 7, hxsrmeng@gmail.com wrote:
> > 
> > The /dev/md0 is set as RAID0
> > "cat /proc/mdstat" shows
> > md0 : active raid0 sda1[0] sdd1[3] sdc1[2] sdb1[1]
> > 157307904 blocks 64k chunks
> > 
> > Then sdd is removed.
> > 
> > But  "cat /proc/mdsta" still shows the same information as above, while two
> > RAID5 devices show their sdd parts as (F)
> > md0 : active raid0 sda1[0] sdd1[3] sdc1[2] sdb1[1]
> > 157307904 blocks 64k chunks
> > 
> > Is this normal?
> 
> Yes.
> 
> raid0 is not real raid.  It is not able to cope with disk failures, so
> it doesn't even try.  Devices in a raid0 are never marked failed as
> doing so would be of no benefit.
> 
> NeilBrown
> 
>