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Using S.M.A.R.T. Disk Monitor 127

follow up with the -scrub family of read commands, run the -steb , and repeat. This tests every component

of the device including every block of media as well as the electronics components. Seagate recommends using the

E6 pattern as it will generally sniff out more weak sectors that would need to be remapped.

What about host overhead?

SMARTMonUX sends only one I/O command to write 30MB at a time. Even measuring this amount of overhead

generates a higher load then zeroing your disk. (Note, due to the pass-through I/O limitations unique to SGI's IRIX

operating system, the -scrub family of commands will run significantly slower on that platform. (That is because the

O/S does not support multiple concurrent pass-through commands to the same device, the handle must be opened &

closed between I/Os.). These limitations will not affect the ANSI-type self-test commands, and they will not be

noticeable with the write same commands since they might generate only one or two I/Os per second.

Is this a safe operation?

It is safe to do this on any disk other than your O/S disk and any disks required by your O/S, such as swap, to stay

alive. Of course, all data will be destroyed on that disk, but it will not hurt the drive. In fact, storage manufacturers use

the write-same command as means of stress testing drives to make weak sectors fail so those defects can be

remapped.

How long does this take?

A fast 73 GB disk typically completes in around 15 minutes.

How do I test really large devices, like a 5 TB LUN on a RAID controller?

Append the -16 function, which instructs the software to send 16-byte SCSI commands. These commands are

required for devices greater than the approximately 2.1 TB limitation for the 10-byte SCSI commands.

1.36 Spin Disk Up and Down

These commands are supported on SCSI, SAS, and Fibre Channel Disks. They let you query whether the selected

disk is currently spun up, spun down, or in a transitional state.

Spin Up

The -spinup command sends the SCSI START UNIT command to the selected disk, which causes it to spin up. If

the drive is already spun up, then the command will be ignored. This version of the spin-up command waits for the

disk to complete the spin-up process before returning the results.

Reasons for using spin up/down

· You can simulate a type of a drive failure by spinning a disk down, and add delays to benchmarks for situations

when you want to see what will happen to some hardware when it is under stress.

· Sometimes JBOD-attached fibre channel disks will spin down if they have not been accessed for a while. Use the

spin-up either as a stand-alone command, or a background job to prevent a system from spinning disks down.

· If you have a subsystem that will not be accessed for a while, and your host O/S allows, you can spin it down to

conserve power as part of a green initiative.

# ./smartmon-ux -spinup /dev/rdsk/c4t16d0s0

Discovered SEAGATE ST3146855SS S/N "3LN27XJ9" on /dev/rdsk/c4t16d0s0 (Not Enabling SMART)(140014 MB)

The disk is now spun up

Program Ended.

(The reported results for this and subsequent commands, with exception of the spin inquiry, will be the same

regardless of whether the disk is currently up, down, or in a transitional state)

Spin Up Immediate

The -spinupi command sends the SCSI START UNIT IMMEDIATE command to the selected disk. Results are

similar to START UNIT, but the command is sent to the disk, and does not wait for the drive to spin up before it

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