isw: array length calculation seems to be wrong

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]


I'm trying to help a user with a problem with their isw set. After upgrading to Ubuntu 11.04 ( 1.0.0.rc16 ) it seems that their partition extends beyond the end of the raid array. I'm looking at how isw computes the array length and it seems to be wrong. It looks like _cal_array_size() computes the length of the ( raid1 ) array by finding the smallest component disk and subtracting some reserved blocks. This does not seem to be correct. Relevant fields from the user's metadata:

0x0e8 disk[0].totalBlocks: 1953523055
0x118 disk[1].totalBlocks: 1953525168
0x148 isw_dev[0].SizeLow: 1953519616
0x1ac isw_dev[0].vol.map[0].blocks_per_member: 1953519880
0x1b0 isw_dev[0].vol.map[0].num_data_stripes: 7630936
0x1b4 isw_dev[0].vol.map[0].blocks_per_strip: 128

Further, it looks like create_rd() sets the size of each component disk to the same thing anyhow:

if ((r->sectors = dev->vol.map[0].blocks_per_member - RAID_DS_JOURNAL))

This seems to have given the user a block device with a total size of 1953519880 sectors. Debian and Ubuntu are carrying a patch that removes the subtraction of RAID_DS_JOURNAL above, or the array would be even smaller. This seems to have been added because a Debian user had a similar shrinkage of their disk after an upgrade. As you can see, the array size seems to be exactly equal to blocks_per_member, even though _cal_array_size() appears to be subtracting DISK_RESERVED_BLOCKS, which should make it a few hundred sectors smaller. I am not sure why this is.

I believe that the array size should be correctly computed as blocks_per_strip * num_data_stripes. That appears to be off by a factor of two however, so maybe blocks_per_strip is actually in kb instead of sectors? Correcting for that gives an array length of 1953519616 sectors. This matches isw_dev[0].SizeLow. Perhaps this field should be used directly since it gives the correct size, instead of doing any calculations?

_______________________________________________
Ataraid-list mailing list
Ataraid-list@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/ataraid-list


[Linux RAID]     [Linux IDE]     [Linux SCSI]     [Kernel]     [Linux Books]     [Linux Admin]     [GFS]     [RPM]     [Photos]     [Yosemite Photos]     [Yosemite News]     [AMD 64]
  Powered by Linux