Failure to restore data from a failed/incomplete backup

Issue
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Cannot restore of data from a failed backup. On issuing a cbrestore command, the .wal file size shrinks to 0 and restore is not able to read any data to complete the restore operation
and throws this error -
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Traceback (most recent call last):
File "/opt/couchbase/lib/python/cbrestore", line 250, in <module>
main()
File "/opt/couchbase/lib/python/cbrestore", line 185, in main
db.executemany("attach ? as ?", zip(db_filenames, attached_dbs))
sqlite3.OperationalError: too many attached databases - max 10
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Steps to reproduce
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Load 1M of data : [/opt/couchbase/bin/memcachetest -h localhost:11211 -i 1000000 -M 1024 -K cb_2 -l ]
Run a backup of the data [ while database is online] : sudo -su couchbase /opt/couchbase/bin/cbbackup /opt/couchbase/var/lib/couchbase/data/default-data/default /tmp/rev7
Copy data from /../default-data to backup folder - [ cp -r /opt/couchbase/var/lib/couchbase/data/default-data/ /tmp/rev7/*]
Run a restore [sudo /opt/couchbase/bin/cbrestore -H localhost:11211 /tmp/rev7/default*]

Error
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Traceback (most recent call last):
File "/opt/couchbase/lib/python/cbrestore", line 250, in <module>
main()
File "/opt/couchbase/lib/python/cbrestore", line 185, in main
db.executemany("attach ? as ?", zip(db_filenames, attached_dbs))
sqlite3.OperationalError: too many attached databases - max 10

ls -lt -h /tmp/rev7/*

Before Restore
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rw-rr- 1 ketaki ketaki 13M 2012-04-17 09:21 /tmp/rev7/default-wal
rw-rr- 1 ketaki ketaki 128K 2012-04-17 09:21 /tmp/rev7/default-shm
rw-rr- 1 ketaki ketaki 824M 2012-04-17 09:21 /tmp/rev7/default-3.mb-wal
rw-rr- 1 ketaki ketaki 6.4M 2012-04-17 09:21 /tmp/rev7/default-3.mb-shm
-rwxrwxrwx 1 couchbase couchbase 477M 2012-04-17 09:21 /tmp/rev7/default-3.mb
rw-rr- 1 ketaki ketaki 820M 2012-04-17 09:21 /tmp/rev7/default-2.mb-wal
rw-rr- 1 ketaki ketaki 6.3M 2012-04-17 09:21 /tmp/rev7/default-2.mb-shm
-rwxrwxrwx 1 couchbase couchbase 478M 2012-04-17 09:21 /tmp/rev7/default-2.mb
rw-rr- 1 ketaki ketaki 821M 2012-04-17 09:20 /tmp/rev7/default-1.mb-wal
rw-rr- 1 ketaki ketaki 6.3M 2012-04-17 09:20 /tmp/rev7/default-1.mb-shm
-rwxrwxrwx 1 couchbase couchbase 477M 2012-04-17 09:20 /tmp/rev7/default-1.mb
rw-rr- 1 ketaki ketaki 820M 2012-04-17 09:20 /tmp/rev7/default-0.mb-wal
rw-rr- 1 ketaki ketaki 6.3M 2012-04-17 09:20 /tmp/rev7/default-0.mb-shm
-rwxrwxrwx 1 couchbase couchbase 477M 2012-04-17 09:20 /tmp/rev7/default-0.mb
-rwxrwxrwx 1 couchbase couchbase 1.0K 2012-04-17 09:20 /tmp/rev7/default

After issuing restore
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ketaki@ubu-0101:/opt/couchbase$ ls -lt /tmp/rev7/*
-rwxrwxrwx 1 couchbase couchbase 499994624 2012-04-17 09:26 /tmp/rev7/default-3.mb
rw-rr- 1 ketaki ketaki 6619136 2012-04-17 09:26 /tmp/rev7/default-3.mb-shm
rw-rr- 1 root root 0 2012-04-17 09:25 /tmp/rev7/default-2.mb-shm
rw-rr- 1 root root 0 2012-04-17 09:25 /tmp/rev7/default-2.mb-wal
-rwxrwxrwx 1 couchbase couchbase 545611776 2012-04-17 09:25 /tmp/rev7/default-2.mb
rw-rr- 1 root root 0 2012-04-17 09:25 /tmp/rev7/default-1.mb-shm
rw-rr- 1 root root 0 2012-04-17 09:25 /tmp/rev7/default-1.mb-wal
-rwxrwxrwx 1 couchbase couchbase 545002496 2012-04-17 09:24 /tmp/rev7/default-1.mb
rw-rr- 1 root root 0 2012-04-17 09:24 /tmp/rev7/default-0.mb-shm
rw-rr- 1 root root 0 2012-04-17 09:24 /tmp/rev7/default-0.mb-wal
-rwxrwxrwx 1 couchbase couchbase 544702464 2012-04-17 09:24 /tmp/rev7/default-0.mb
-rwxrwxrwx 1 couchbase couchbase 52224 2012-04-17 09:23 /tmp/rev7/default
rw-rr- 1 ketaki ketaki 863795168 2012-04-17 09:21 /tmp/rev7/default-3.mb-wal
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