User manual

Using S.M.A.R.T. Disk Monitor 217
SANTOOLS® is registered in US Patent and Trademark Office No 3,107,854 All rights reserved.
storage system will declare a hard error and reallocate the sector by mapping out the bad sector and
substituting an unused, reserved sector. The use of these corrective operations and reallocation
functions can require a significant amount of time during retrieval of user data and thus, limit the
maximum data transfer rate of the data storage system."
It does not matter whether you are using JBOD, hardware RAID or software-based RAID, BGMS will provide
profound improvement in reliability and data integrity with near-zero overhead.
Benefits of BGMS
First, BGMS will fix bad blocks on-the-fly as they are discovered by the firmware. The disk drive will use idle time to
perform multiple re-reads to correct the data. As the bad blocks are discovered BEFORE the O/S actually needs the
data on those blocks, then no programs have to suspend processing while bad blocks are repaired. If your host is
streaming movies into hotel rooms, then user's won't suffer through the experience of a movie stopping for 5-30
seconds while the host and/or RAID subsystem go through the data recovery/remapping process.
If you are using software RAID, then BGMS can somewhat replace data consistency checks, and provide somewhat
self-healing storage farms. In the event the BGMS-enabled disk can not repair a bad block, then you can use the
report SMARTMonUX generates to provide you a list of physical disk drives and offsets where you know you have
unrecoverable data. You can then use a shell script to find bad blocks , then either run a parity rebuild, or issue a
single command to repair the bad stripe by reading the part of the RAID volume that incorporates the bad block(s).
By issuing a read, the RAID software will discover for itself that there is unreadable data and it will fix it for you.
By exploiting the power of BGMS, you could effectively scan and repair any size storage farm 24x7 without the
inherent overhead when the host tries to scan & repair bad blocks via brute-force techniques.
Disable Background Media Scanning
The -bmsd command disables background media scanning.
Usage
smartmon-ux -bmsd DeviceList
Enable Background Media Scanning
The -bmse command disables background media scanning.
Usage
smartmon-ux -bmse n DeviceList
Where: n represents the hourly scanning interval. Once the disk is programmed to enable scanning, the disk will
automatically begin a new scan after the supplied interval. If disk power is lost, the timer will automatically reset to
zero, and scanning will automatically continue. Send the -bmsd command to stop and disable scanning.
Report Background Media Scan Results
The -bmsr command disables background media scanning.
Usage
smartmon-ux -bmsr DeviceList
The command below was run on a SPARC Solaris 10 system that has 6 SAS disks. We added the time command to
the prompt so that you can see how quickly the command runs. This was also run with wild-cards to select all disks
attached to controller #4.
# time ./smartmon-ux -bmsr /dev/rdsk/c4*s0
SMARTMon-UX [Release 1.36, Build 8-JUN-2008] - Copyright 2001-2008 SANtools(R), Inc. http://www.SANtools.
com
Discovered SEAGATE ST3146855SS S/N "3LN23ER0" on /dev/rdsk/c4t12d0s0 (Not Enabling SMART)(140014 MB)
Background Media Scan Report @ Sun Jun 8 16:33:03 2008
Accumulated power-on minutes: 135086 [94 days]
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