User manual

Using S.M.A.R.T. Disk Monitor 111
SANTOOLS® is registered in US Patent and Trademark Office No 3,107,854 All rights reserved.
that run and report self-tests
Q. Can I test tape drives?
A. Yes, absolutely. We have examples in this section of running self-tests on a cartridge tape drive. Remember, the
self-test is a feature of the firmware.
Q. I am having problems running self-tests on USB-attached devices, or some SATA disks. What is wrong?
A. The most common problem with USB and SATA/ATA disks is that the command isn't getting properly translated to
the disk. When you hook up a ATA/SATA device to a USB port, part of the process is that a bridge chip translates the
native ATA commands that the disk uses to SCSI commands that the USB protocol uses. The low-level commands
that run and report self-tests are incompatible. Unless the manufacturer of your USB enclosure took great care to
properly integrate the necessary translation, then it just won't work. The vast majority of external USB devices will
NOT do the translation properly. Don't blame them as they are more concerned with supporting reads & writes. The
bottom line is that if you want to perform self-tests on USB mounted peripherals, then you are going to have to hook
them up via a native ATA or SATA controller.
There is a similar problem with many of the low-end RAID controllers on motherboards. If your ATA disks appear as
SCSI devices, then the RAID controller is performing protocol translation, and their chip may have the same problem
Other RAID vendors get around the problem by providing a proprietary programming interface that allows a developer
to encapsulate commands so that they work properly.
Q. How does the smartmon-us -verify differ from a self-test?
A. The -verify command will provide you a full list of unreadable blocks. It will not test electronics, or even make sure
that the disk can write anything at all. However, unlike the self-test, a self-test will terminate on the first bad block.
Furthermore a self-test will not verify the media. It is more likely to never even discover that you have a bad block. If
you need to determine if you have unreadable data, then use the -verify command. If you need to do full testing of a
disk to make sure it is burned in and safe for use, then run both a -verify, and a self-test, then follow up with the -dft
family of commands to perform some destructive write tests.
Q. Can I run self-tests on mounted disk drives?
A. Background tests, per the specification, are not supposed to prevent your host O/S from using the disks
concurrently to read and write to. We do this all the time in windows laptops and never have any problems (This does
not mean that it is safe, we are just saying we have not had any problems).. However, the safest thing to do before
performing tests is to make sure they are not mounted. This allows you to run the potentially more extensive
foreground tests. If the disks do not have any data on them, then you can also run destructive tests that verify that the
media is OK.
SANtools' official policy is to check with your storage vendor to see if it is 'safe' to run self-tests on systems
with live data.
1.33 Secure Erase and Validation
The secure erase function wipes out data on the disk per the US Department of Defense standard DoD 5220.22-M
specification. (Note, the specification requires three full triple-pass iterations for DoD compliance). This function is
reserved for SCSI, SAS, SSA, and Fibre Channel disks only.
SMARTMon-UX has several commands relating to secure erase:
-securecheckall Scans the entire disk, and reports the count and standard deviation for all 256 possible byte
values on the
entire disk.
-securecheck n This performs the action in the same way as -securecheck, but it will automatically terminate
after either
a user-specified amount of time, or after it determines that the data is not random, whichever
comes first.
-secure This is the function that implements the secure erase.
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