Re: [git patch] 2.6.x libata fix

[Matt Darcy <kernel-lists@projecthugo.co.uk>]

>
>
> I can now provide further updates for this, although this are not 
> really super useful.
>
> I've copied the linux-raid list in as well, as after a little more 
> testing on my part I'd appriciate some input from the raid guys also.
>
> First of all, please ignore the comments above, there was a problem 
> with grub and it actually "failed back" and booted into the older git 
> release, so my initial test was actually done running the wrong kenel 
> which I didn't notice. Appologies to all for this.
>
> Last nights tests where done using the correct kernel (I fixed the 
> grub typo) 2.6.15-g5367f2d6
>
> The details I have are as follows.
>
> I can run the machine accessing the 7 maxtor SATA disks as individual 
> disks for around 12 hours now, without any hangs or errors or any real 
> problems. I've not hit them very hard, but initial performance seems 
> fine and more than usable.
>
> The actual problems occurr when including these disks in a raid group.
>
> root@berger:~# fdisk -l /dev/sdc
>
> Disk /dev/sdc: 251.0 GB, 251000193024 bytes
> 255 heads, 63 sectors/track, 30515 cylinders
> Units = cylinders of 16065 * 512 = 8225280 bytes
>
>   Device Boot      Start         End      Blocks   Id  System
> /dev/sdc1               1       30515   245111706   fd  Linux raid 
> autodetect
>
> root@berger:~# fdisk -l /dev/sde
>
> Disk /dev/sde: 251.0 GB, 251000193024 bytes
> 255 heads, 63 sectors/track, 30515 cylinders
> Units = cylinders of 16065 * 512 = 8225280 bytes
>
>   Device Boot      Start         End      Blocks   Id  System
> /dev/sde1               1       30515   245111706   fd  Linux raid 
> autodetect
>
>
> As you can see from my two random disks examples, they are partitioned 
> and makred as raid auto detect.
>
> I issue the mdadm command to build the raid 5 array
>
> mdadm -C /dev/md6 -l5 -n6 -x1 /dev/sdc1 /dev/sdd1 /dev/sde1 /dev/sdf1 
> /dev/sdg1 /dev/sdh1 /dev/sdi1
>
> and the array starts to build.......
>
> md6 : active raid5 sdh1[7] sdi1[6](S) sdg1[4] sdf1[3] sde1[2] sdd1[1] 
> sdc1[0]
>      1225558080 blocks level 5, 64k chunk, algorithm 2 [6/5] [UUUUU_]
>      [>....................]  recovery =  0.1% (374272/245111616) 
> finish=337.8min speed=12073K/sec
>
>
> however at around %25 - %40 completion the box will simpley just hang 
> - I'm getting no on screen messages and the sylog is not reporting 
> anything.
>
> SysRQ is unusable.
>
> I'm open to options on how to resolve this and move the driver forward 
> (assuming it is the drivers interfaction with the raid sub system)
> or
> how to get some meaningful debug out to report back to the appropriate 
> development groups.
>
> thanks.
>
> Matt.
>
>
>
Further further information

The speed that the raid array is being built att appears to drop as the 
array is created

[=====>...............]  recovery = 29.2% (71633360/245111616) 
finish=235.1min speed=12296K/sec
[=====>...............]  recovery = 29.3% (71874512/245111616) 
finish=235.2min speed=12269K/sec
[=====>...............]  recovery = 29.4% (72115872/245111616) 
finish=236.0min speed=12209K/sec
[=====>...............]  recovery = 29.7% (72839648/245111616) 
finish=237.4min speed=12091K/sec
[=====>...............]  recovery = 29.8% (73078560/245111616) 
finish=238.6min speed=12010K/sec
[=====>...............]  recovery = 29.8% (73139424/245111616) 
finish=350.5min speed=8176K/sec
[=====>...............]  recovery = 29.8% (73139424/245111616) 
finish=499.6min speed=5735K/sec
[=====>...............]  recovery = 29.8% (73139776/245111616) 
finish=691.0min speed=4147K/sec

Now the box is hung

I didn't notice this until about %20 through the creation of the array 
then I started paying attention to this. These snap shots are taken 
every 30 seconds

So the problem appears to sap bandwidth on the card to the point there 
the box hangs.

This may have some relevance, or it may not, but worth mentioning at least.

Matt










[=====>...............]  recovery = 29.8% (73139424/245111616) 
finish=350.5min speed=8176K/sec