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Re: Backup to Tape Incomplete

From: "Phillip Smith" <phillip(dot)smith(at)weatherbeeta(dot)com(dot)au>
To:
Cc: <pgsql-admin(at)postgresql(dot)org>
Subject: Re: Backup to Tape Incomplete
Date: 2008-02-28 02:32:00
Message-ID: 02e901c879b2$18ee0210$9b0014ac@wbaus090 (view raw or flat)
Thread:
Lists: pgsql-admin
"Scott Marlowe" <scott(dot)marlowe(at)gmail(dot)com> writes:
> > I wonder what it's meaning by invalid arg?
> 
> On my Fedora machine, "man write" explains EINVAL thusly:
> 
>        EINVAL fd  is attached to an object which is unsuitable for
writing; or
>               the file was opened with  the  O_DIRECT  flag,  and  either
the
>               address  specified  in buf, the value specified in count, or
the
>               current file offset is not suitably aligned.
> 
> I'm not sure that writing to a tape is quite like O_DIRECT, but the
mention of
> an un-aligned count seems pretty relevant.  If you grant the assumption
that
> the underlying problem is that the tape drive has to be written to in
> multiples of its blocksize, then this supports the idea that a violation
of
> that rule would be reported as EINVAL.

Interesting... If I set the block-size to 32, everything goes without any
error,
But not ending with "PostgreSQL database dump complete":

[postgres(at)stirling ~]$ mt setblk 32
[postgres(at)stirling ~]$ mt stat
SCSI 2 tape drive:
File number=0, block number=0, partition=0.
Tape block size 32 bytes. Density code 0x25 (DDS-3).
Soft error count since last status=0
General status bits on (41010000):
 BOT ONLINE IM_REP_EN
[postgres(at)stirling ~]$ pg_dump dbname > /dev/st0
[postgres(at)stirling ~]$ tail - < /dev/st0
REVOKE ALL ON TABLE stock_test FROM dbuser;
GRANT ALL ON TABLE stock_test TO dbuser;
GRANT ALL ON TABLE stock_test TO PUBLIC;


--
-- Name: stores; Type: ACL; Schema: public; Owner: dbuser
--

[postgres(at)stirling ~]$


If I set the block-size to 0... Well it's really not happy:

[postgres(at)stirling ~]$ mt setblk 0
[postgres(at)stirling ~]$ mt stat
SCSI 2 tape drive:
File number=0, block number=0, partition=0.
Tape block size 0 bytes. Density code 0x25 (DDS-3).
Soft error count since last status=0
General status bits on (41010000):
 BOT ONLINE IM_REP_EN
[postgres(at)stirling ~]$ pg_dump dbname > /dev/st0
[postgres(at)stirling ~]$ tail - < /dev/st0
tail: error reading `standard input': Cannot allocate memory
[postgres(at)stirling ~]$ cat /dev/st0 > /tmp/test-restore.sql
cat: /dev/st0: Cannot allocate memory
[postgres(at)stirling ~]$


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