Re: Kernel 2.6.17 and RAID5 Grow Problem (critical section backup)

[Justin Piszcz <jpiszcz@lucidpixels.com>]

On Fri, 7 Jul 2006, Justin Piszcz wrote:

> On Fri, 7 Jul 2006, Justin Piszcz wrote:
>
>> p34:~# mdadm /dev/md3 -a /dev/hde1
>> mdadm: added /dev/hde1
>> 
>> p34:~# mdadm -D /dev/md3
>> /dev/md3:
>>        Version : 00.90.03
>>  Creation Time : Fri Jun 30 09:17:12 2006
>>     Raid Level : raid5
>>     Array Size : 1953543680 (1863.04 GiB 2000.43 GB)
>>    Device Size : 390708736 (372.61 GiB 400.09 GB)
>>   Raid Devices : 6
>>  Total Devices : 7
>> Preferred Minor : 3
>>    Persistence : Superblock is persistent
>>
>>    Update Time : Fri Jul  7 08:25:44 2006
>>          State : clean
>> Active Devices : 6
>> Working Devices : 7
>> Failed Devices : 0
>>  Spare Devices : 1
>>
>>         Layout : left-symmetric
>>     Chunk Size : 512K
>>
>>           UUID : e76e403c:7811eb65:73be2f3b:0c2fc2ce
>>         Events : 0.232940
>>
>>    Number   Major   Minor   RaidDevice State
>>       0      22        1        0      active sync   /dev/hdc1
>>       1      56        1        1      active sync   /dev/hdi1
>>       2       3        1        2      active sync   /dev/hda1
>>       3       8       49        3      active sync   /dev/sdd1
>>       4      88        1        4      active sync   /dev/hdm1
>>       5       8       33        5      active sync   /dev/sdc1
>>
>>       6      33        1        -      spare   /dev/hde1
>> p34:~# mdadm --grow /dev/md3 --raid-disks=7
>> mdadm: Need to backup 15360K of critical section..
>> mdadm: Cannot set device size/shape for /dev/md3: No space left on device
>> p34:~# mdadm --grow /dev/md3 --bitmap=internal --raid-disks=7
>> mdadm: can change at most one of size, raiddisks, bitmap, and layout
>> p34:~# umount /dev/md3
>> p34:~# mdadm --grow /dev/md3 --raid-disks=7
>> mdadm: Need to backup 15360K of critical section..
>> mdadm: Cannot set device size/shape for /dev/md3: No space left on device
>> p34:~#
>> 
>> The disk only has about 350GB of 1.8TB used, any idea why I get this error?
>> 
>> I searched google but could not find anything on this issue when trying to 
>> grow the array?
>> 
>> 
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>
> Is it because I use a 512kb chunksize?
>
> Jul  7 08:44:59 p34 kernel: [4295845.933000] raid5: reshape: not enough 
> stripes.  Needed 512
> Jul  7 08:44:59 p34 kernel: [4295845.962000] md: couldn't update array info. 
> -28
>
> So the RAID5 reshape only works if you use a 128kb or smaller chunk size?
>
> Justin.
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>From the source:

/* Can only proceed if there are plenty of stripe_heads.
@@ -2599,30 +2593,48 @@ static int raid5_reshape(mddev_t *mddev,
* If the chunk size is greater, user-space should request more
* stripe_heads first.
*/
- if ((mddev->chunk_size / STRIPE_SIZE) * 4 > conf->max_nr_stripes) {
+ if ((mddev->chunk_size / STRIPE_SIZE) * 4 > conf->max_nr_stripes ||
+ (mddev->new_chunk / STRIPE_SIZE) * 4 > conf->max_nr_stripes) {
printk(KERN_WARNING "raid5: reshape: not enough stripes. Needed %lu\n",
(mddev->chunk_size / STRIPE_SIZE)*4);
return -ENOSPC;
}

I don't see anything that mentions one needs to use a certain chunk size?

Any idea what the problem is here?

Justin.