FWIW -- xfs-oss, included as 'last line' was of minor interest; known bug on
this kernel?:
Linux Ishtar 2.6.35.7-T610-Vanilla-1 #2 SMP PREEMPT Mon Oct 11 17:19:41
PDT 2010 x86_64 x86_64 x86_64 GNU/Linux
PÃdraig Brady wrote:
On 23/02/11 04:30, Linda Walsh wrote:
I understand, somewhat, what is happening. I have two different utils,
'dd' and mbuffer both of which have a 'direct' option to write to disk.
mbuffer was from my distro with a direct added, which is
I'm not sure if it's truncating the write to the lower bound of the
sector size or the file-allocation-unit size but from a {dump|cat},
piped into {cat, dd mbuffer}, the output sizes are:
file size delta
------------- ---------- ----
dumptest.cat 5776419696
dumptest.dd 5776343040 76656
dumptest.mbuff 5368709120 407710576
- params:
dd of=dumptest.dd bs=512M oflag=direct
mbuffer -b 5 -s 512m -direct -f -o dumptest.mbuff
----
I'm not aware of what either did, but no doubt neither expected an
error in the final write and didn't handle the results properly.
Vanilla kernel 2.6.35-7 x86_64 (SMP PREMPT)
Note dd will turn off O_DIRECT for the last write
if it's less than the block size.
http://git.savannah.gnu.org/gitweb/?p=coreutils.git;a=commitdiff;h=5929322c
------
FWIW, 'dd' is from 'coreutils-7.1-3.2.x86_64' (from the suse 11.2 release):
While I used dump (xfsdump to be precise) to produce my initial output
to mbuffer, it was the error message at the end which caught my attention.
Prior I had a tried a series of filters after the initial mem-to-mem
buffer performed by 'dd', then later 'mbuffer'. The filters were
successively lower-io compress options over the years as disk and
network speeds rose and cpu-compression became the choke-point.
(xfsdump -b 512m )|(initially 'dd', later, 'mbuffer' )| \
(su -f -m backup -c "$umask $um;${Compress:-} ${Compress_ops:-} \
>${Dmpfile}${Compress_ext}" )
---
Eventually I wanted to get rid of the final filter step altogether and
have that 'buffer' statement after the 'dump' go direct to disk, then
later "--direct" to disk...
It was adding the 'DIRECT' flag then that I noticed mbuffer's error.
My first debug step was to go for a shorter dump file (the one that
failed on was over 3TB and took over 3h to reproduce). Then I substituted
'cat' as that final filter and ended up with my 'testfile' I used for later
tests for 'mbuffer' and 'dd'.
NOTE:
I tried using the 'iflag=fullblock' as you recommend and it made the problem
'consistent' with the output of 'mbuffer', i.e. it transfered less data
and the truncation was consistent with a 512M divisor, indicating it was
'cat' default record output size that was causing the difference.
If I use 'dd' to read the base file (no direct i/o) I get consistent results
with 'mbuffer' and 'dd':
Input: DumpTest.out: 5776419696
Output file sizes are as reported by 'dd', with 'test1' giving the closest
answer (short record line concatenated with ' & '):
test1> cat DumpTest.out |dd of=dumptest.dd-fb oflag=direct
bs=512M
dd: writing `dumptest.dd-fb': Invalid argument
0+7346 records in & 0+7345 records out
5776343040 bytes (5.8 GB) copied, 12.4361 s, 464 MB/s
test2> cat DumpTest.out |dd of=dumptest.dd+fb oflag=direct bs=512M
iflag=fullblock
dd: writing `dumptest.dd+fb': Invalid argument
10+1 records in & 10+0 records out
5368709120 bytes (5.4 GB) copied, 12.581 s, 427 MB/s
test3> dd if=DumpTest.out bs=512M |dd of=dumptest2.dd+fb oflag=direct
bs=512M iflag=fullblock
10+1 records in & 10+1 records out
5776419696 bytes (5.8 GB) copieddd: writing `dumptest2.dd+fb', 11.6493
s, 496 MB/s
: Invalid argument
10+1 records in & 10+0 records out
5368709120 bytes (5.4 GB) copied, 11.6513 s, 461 MB/s
test4> dd if=DumpTest.out bs=512M |dd of=dumptest2.dd-fb oflag=direct
bs=512M
10+1 records in & 10+1 records out
dd: writing `dumptest2.dd-fb'5776419696 bytes (5.8 GB) copied, 11.4503
s, 504 MB/s
: Invalid argument
10+1 records in & 10+0 records out
5368709120 bytes (5.4 GB) copied, 11.4503 s, 469 MB/s
---
I've tried significantly shorter files and NOT had this problem
(record size=64k, and 2 files one @ 57k and one at 64+57k). Both copied
fine.
Something to do with large file buffers.
Of *SIGNIFICANT* note. In trying to create an empty file of the size
used, from scratch, using 'xfs_mkfile', I got an error:
xfs_mkfile 5776419696 testfile
pwrite64: Invalid argument
---
I'm having problems generating new kernels (will ask in separate
message) so will have to fix those before moving ahead...
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