> Try to set bigger segment size for your BLOB. 1 byte is too small.
>Try 2000.
> Usually applications don't use segment size anywhere but isql may
>respect it and receiving BLOB byte-by-byte may be the source of
>slowness.

Good point, but didn't help :-(

/opt/firebird/bin/isql -u SYSDBA -p masterkey /tmp/r1.fdb
SQL> show table testdata;
IOBJID BIGINT Not Null
BDATA BLOB segment 4096, subtype UNKNOWN Nullable
CONSTRAINT PK_TESTDATA:
Primary key (IOBJID)
SQL>

time /opt/firebird/bin/isql -u SYSDBA -p masterkey /tmp/r1.fdb -i inputfile

> output.txt

real 1m38.099s
user 0m0.147s
sys 0m0.203s


Anybody else is using blobs on linux?