Re: [Bacula-users] btape vs. dd: Strange behavior on LTO-5

Hi Andreas,

I have exactly the same problem with LTO-4 drives.  I don't have an 
answer, just a me too.  I've ignored this for a long time just because 
it worked with 128K blocks.

I am currently rebuilding a server based on CentOS 6.4, 
2.6.32-358.18.1.el6.x86_64 #1 SMP Wed Aug 28 17:19:38 UTC 2013 x86_64 
x86_64 x86_64 GNU/Linux.

I just got everything compiled, and here is the output using 256K blocks.

# ./btape -c ../etc/bacula-sd.conf Tape
Tape block granularity is 1024 bytes.
btape: butil.c:290-0 Using device: "Tape" for writing.
btape: btape.c:477-0 open device "Tape" (/dev/nst0): OK
*rewind
btape: btape.c:579-0 Rewound "Tape" (/dev/nst0)
*test

=== Write, rewind, and re-read test ===

I'm going to write 10000 records and an EOF
then write 10000 records and an EOF, then rewind,
and re-read the data to verify that it is correct.

This is an *essential* feature ...

btape: btape.c:1157-0 Wrote 10000 blocks of 262044 bytes.
btape: btape.c:609-0 Wrote 1 EOF to "Tape" (/dev/nst0)
btape: btape.c:1173-0 Wrote 10000 blocks of 262044 bytes.
btape: btape.c:609-0 Wrote 1 EOF to "Tape" (/dev/nst0)
btape: btape.c:1215-0 Rewind OK.
Got EOF on tape.
btape: btape.c:1233-0 Read block 3617 failed! ERR=Success
*quit

On 08/21/2013 01:20 PM, Andreas Koch wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> Hi all,
>
> I am stumped by the behavior of an HP LTO-5 drive running on Scientific
> Linux 6.4 (Kernel 2.6.32-358.14.1.el6.x86_64) and Bacula 5.2.12.
> Specifically, using dd, I can read and write block sizes of 2 MB, but btape
> cannot reliably handle anything larger than 128 KB (fails on reading, see
> below).
>
> However, when I read the tape that btape supposedly has written two files of
> 10000 blocks each (and then fails after reading 3616 of them) using dd, I
> read each of btape-written 10000-block ``files'' as _three_ actual tape
> files (of 3616+3616+2768=10000 blocks). Note that this test was performed
> with a block size of 512KB (see Device definition from bacula-sd.conf, below).
>
> I would be grateful for any ideas on how to resolve this. With the smaller
> block sizes, the backup is noticeably slower for compressible data (e.g.,
> database dumps), so I really would like to move back up to larger block sizes.
>
> Many thanks in advance,
>    Andreas Koch
>
> gundabad ~ # btape -c /etc/bacula/bacula-sd.conf /dev/nst0
> Tape block granularity is 1024 bytes.
> btape: butil.c:290 Using device: "/dev/nst0" for writing.
> btape: btape.c:477 open device "LTO-4" (/dev/nst0): OK
> *test
>
> === Write, rewind, and re-read test ===
>
> I'm going to write 10000 records and an EOF
> then write 10000 records and an EOF, then rewind,
> and re-read the data to verify that it is correct.
>
> This is an *essential* feature ...
>
> btape: btape.c:1157 Wrote 10000 blocks of 524188 bytes.
> btape: btape.c:609 Wrote 1 EOF to "LTO-4" (/dev/nst0)
> btape: btape.c:1173 Wrote 10000 blocks of 524188 bytes.
> btape: btape.c:609 Wrote 1 EOF to "LTO-4" (/dev/nst0)
> btape: btape.c:1215 Rewind OK.
> Got EOF on tape.
> btape: btape.c:1233 Read block 3617 failed! ERR=Success
> *q
> btape: smartall.c:404 Orphaned buffer: btape 280 bytes at 15e55e8 from 
> jcr.c:362
> gundabad ~ # mt -f /dev/nst0 rewind
> gundabad ~ # dd if=/dev/nst0 of=/dev/null bs=512k
> 3616+0 records in
> 3616+0 records out
> 1895825408 bytes (1.9 GB) copied, 3.7062 s, 512 MB/s
> gundabad ~ # dd if=/dev/nst0 of=/dev/null bs=512k
> 3616+0 records in
> 3616+0 records out
> 1895825408 bytes (1.9 GB) copied, 3.7542 s, 505 MB/s
> gundabad ~ # dd if=/dev/nst0 of=/dev/null bs=512k
> 2768+0 records in
> 2768+0 records out
> 1451229184 bytes (1.5 GB) copied, 2.88829 s, 502 MB/s
> gundabad ~ # dd if=/dev/nst0 of=/dev/null bs=512k
> 3616+0 records in
> 3616+0 records out
> 1895825408 bytes (1.9 GB) copied, 3.75554 s, 505 MB/s
> gundabad ~ # dd if=/dev/nst0 of=/dev/null bs=512k
> 3616+0 records in
> 3616+0 records out
> 1895825408 bytes (1.9 GB) copied, 3.75338 s, 505 MB/s
> gundabad ~ # dd if=/dev/nst0 of=/dev/null bs=512k
> 2768+0 records in
> 2768+0 records out
> 1451229184 bytes (1.5 GB) copied, 2.88846 s, 502 MB/s
> gundabad ~ # dd if=/dev/nst0 of=/dev/null bs=512k
> 0+0 records in
> 0+0 records out
> 0 bytes (0 B) copied, 0.247548 s, 0.0 kB/s
>
> Device {
>    Name = LTO-5
>    Media Type = LTO-5
>    Archive Device = /dev/nst0
>    AutomaticMount = yes;               # when device opened, read it
>    AlwaysOpen = yes;
>    RemovableMedia = yes;
>    RandomAccess = no;
>    Maximum File Size = 8g;
>    Minimum block size = 524288
>    Maximum block size = 524288
>    Changer Device = /dev/changer
>    AutoChanger = yes
>    # AHK we want to interrogate the drive, not the changer
>    Alert Command = "sh -c 'smartctl -H -l error /dev/sg11'"
>    Maximum Spool Size = 3000g
>    Spool Directory = /etc/bacula/spooldisk/BaculaSpool
>    Maximum Network Buffer Size = 65536
> }
>
>
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