I asked my contact at QNAP to comment on some recent posts that have complained about errors and slow speed of backups made to USB drives. This is the response I received from QNAP (edited for format and clarity).
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1) Our implementation of "backup to external storage feature" is based on standard Linux "copy" and "rsync" commands. It allows server managers to back up the selected share folders to the external USB disk instantly or by schedule.
2) For the file disappearance issue described in this thread
http://forum.qnap.com/viewtopic.php?f=15&t=10704&p=50465
The failure of copied files to show up can be due to SAMBA not updating quickly. Reconnecting to the share in question should force an update and the user should be able to see the files.
We have investigated and answered other complaints of file copy problems via private message. We found that some issues were due to the USB or eSATA drive used. We have found that some inexpensive drives or drive enclosures do not provide reliable file transfer.
In some cases, replacing the USB or eSATA cable might help. But other problems can be caused by USB-to-SATA bridge chip incompatibility. In that case a different drive or enclosure must be used.
3) Slow backup speed
The current NTFS 3G (refered to in http://forum.qnap.com/viewtopic.php?f=13&t=10484&p=50067) provides the read/write capability for external storage.
We have seen the slow performance (for a 500MHz Marvell ARM, NTFS-3G performance is currently around 2-3MB/s) and have already spent some effort for several months to work/develop with Paragon for a better NTFS-write solution.
The work with Paragon's has yielded a solution that can provide approximately 10MB/s throghput. But we don't yet have a stable release, so currently must continue to use the current NTFS-3G based implementation.
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1) Our implementation of "backup to external storage feature" is based on standard Linux "copy" and "rsync" commands. It allows server managers to back up the selected share folders to the external USB disk instantly or by schedule.
2) For the file disappearance issue described in this thread
http://forum.qnap.com/viewtopic.php?f=15&t=10704&p=50465
The failure of copied files to show up can be due to SAMBA not updating quickly. Reconnecting to the share in question should force an update and the user should be able to see the files.
We have investigated and answered other complaints of file copy problems via private message. We found that some issues were due to the USB or eSATA drive used. We have found that some inexpensive drives or drive enclosures do not provide reliable file transfer.
In some cases, replacing the USB or eSATA cable might help. But other problems can be caused by USB-to-SATA bridge chip incompatibility. In that case a different drive or enclosure must be used.
3) Slow backup speed
The current NTFS 3G (refered to in http://forum.qnap.com/viewtopic.php?f=13&t=10484&p=50067) provides the read/write capability for external storage.
We have seen the slow performance (for a 500MHz Marvell ARM, NTFS-3G performance is currently around 2-3MB/s) and have already spent some effort for several months to work/develop with Paragon for a better NTFS-write solution.
The work with Paragon's has yielded a solution that can provide approximately 10MB/s throghput. But we don't yet have a stable release, so currently must continue to use the current NTFS-3G based implementation.