Hey Max - Check out the on-disk specification document at
http://opensolaris.org/os/community/zfs/docs/.
Page 32 illustration shows the rootbp pointing to a dnode_phys_t
object (the first member of a objset_phys_t data structure).
The source code indicates ub_rootbp is a blkptr_t, which contains
a 3 member array of dva_t 's called blk_dva (blk_dva[3]).
Each dva_t is a 2 member array of 64-bit unsigned ints (dva_word[2]).
So it looks like each blk_dva contains 3 128-bit DVA's....
You probably figured all this out already....did you try using
a objset_phys_t to format the data?
Thanks,
/jim
[EMAIL PROTECTED] wrote:
> Hi All,
> I have modified mdb so that I can examine data structures on disk using
> ::print.
> This works fine for disks containing ufs file systems. It also works
> for zfs file systems, but...
> I use the dva block number from the uberblock_t to print what is at the
> block
> on disk. The problem I am having is that I can not figure out what (if
> any) structure to use.
> All of the xxx_phys_t types that I try do not look right. So, the
> question is, just what is
> the structure that the uberblock_t dva's refer to on the disk?
>
> Here is an example:
>
> First, I use zdb to get the dva for the rootbp (should match the value
> in the uberblock_t(?)).
>
> # zdb -dddd usbhard | grep -i dva
> Dataset mos [META], ID 0, cr_txg 4, 1003K, 167 objects, rootbp [L0 DMU
> objset] 400L/200P DVA[0]=<0:111f79000:200> DVA[1]=<0:506bde00:200>
> DVA[2]=<0:36a286e00:200> fletcher4 lzjb LE contiguous birth=621838
> fill=167 cksum=84daa9667:365cb5b02b0:b4e531085e90:197eb9d99a3beb
> bp = [L0 DMU objset] 400L/200P DVA[0]=<0:111f6ae00:200>
> DVA[1]=<0:502efe00:200> DVA[2]=<0:36a284e00:200> fletcher4 lzjb LE
> contiguous birth=621838 fill=34026
> cksum=cd0d51959:4fef8f217c3:10036508a5cc4:2320f4b2cde529
> Dataset usbhard [ZPL], ID 5, cr_txg 4, 15.7G, 34026 objects, rootbp [L0
> DMU objset] 400L/200P DVA[0]=<0:111f6ae00:200> DVA[1]=<0:502efe00:200>
> DVA[2]=<0:36a284e00:200> fletcher4 lzjb LE contiguous birth=621838
> fill=34026 cksum=cd0d51959:4fef8f217c3:10036508a5cc4:2320f4b2cde529
> first block: [L0 ZIL intent log] 9000L/9000P
> DVA[0]=<0:36aef6000:9000> zilog uncompressed LE contiguous birth=263950
> fill=0 cksum=97a624646cebdadb:fd7b50f37b55153b:5:1
> ^C
> #
>
> Then I run my modified mdb on the vdev containing the "usbhard" pool
> # ./mdb /dev/rdsk/c4t0d0s0
>
> I am using the DVA[0} for the META data set above. Note that I have
> tried all of the xxx_phys_t structures
> that I can find in zfs source, but none of them look right. Here is
> example output dumping the data as a objset_phys_t.
> (The shift by 9 and adding 400000 is from the zfs on-disk format paper,
> I have tried without the addition, without the shift,
> in all combinations, but the output still does not make sense).
>
> > (111f79000<<9)+400000::print zfs`objset_phys_t
> {
> os_meta_dnode = {
> dn_type = 0x4f
> dn_indblkshift = 0x75
> dn_nlevels = 0x82
> dn_nblkptr = 0x25
> dn_bonustype = 0x47
> dn_checksum = 0x52
> dn_compress = 0x1f
> dn_flags = 0x82
> dn_datablkszsec = 0x5e13
> dn_bonuslen = 0x63c1
> dn_pad2 = [ 0x2e, 0xb9, 0xaa, 0x22 ]
> dn_maxblkid = 0x20a34fa97f3ff2a6
> dn_used = 0xac2ea261cef045ff
> dn_pad3 = [ 0x9c2b4541ab9f78c0, 0xdb27e70dce903053,
> 0x315efac9cb693387, 0x2d56c54db5da75bf ]
> dn_blkptr = [
> {
> blk_dva = [
> {
> dva_word = [ 0x87c9ed7672454887,
> 0x760f569622246efe ]
> }
> {
> dva_word = [ 0xce26ac20a6a5315c,
> 0x38802e5d7cce495f ]
> }
> {
> dva_word = [ 0x9241150676798b95,
> 0x9c6985f95335742c ]
> }
> ]
> None of this looks believable. So, just what is the rootbp in the
> uberblock_t referring to?
>
> thanks,
> max
>
>
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