Specifications

ManualsBrandsCradlepoint ManualsComputer equipmentEscape

4) RAID card settings: Native Command Queuing (NCQ)

is supposed to offer better performance by letting the drive

electronics reorder commands for optimized disk access. I

have found that NCQ is not always enabled by default on

the 3ware controllers. It can be turned on manually using

the queuing check box in the Controller Settings page of

3dm or via tw_cli:

# tw_cli /c0/u0 set qpolicy = on

The current setting can be verified on a per-drive basis via

3dm or by using tw_cli:

# tw_cli /c0/p5 show ncq

/c0/p5 NCQ Supported = Yes

/c0/p5 NCQ Enabled = Yes

5) Linux kernel settings: 3ware’s knowledge base has arti-

cles that mention several kernel settings that are supposed

to improve performance over the defaults, but I have not

tried any of those myself.

6) Operational issues: despite all 16 disks being the same

type and firmware version, some of them failed to display their

model number properly in the various 3ware interfaces. For

example, most of the disk model numbers are displayed cor-

rectly—for example, ST31000340AS. But, several show “ST3

INVALID PFM” in the model field. You can see this in the

tw_cli interface. For instance, port 4 displays the model

number properly, but port 5 does not:

# tw_cli /c0/p4 show model

/c0/p4 Model = ST31000340AS

# tw_cli /c0/p5 show model

/c0/p5 Model = ST3_INVALID_PFM

This situation would be intolerable in a system with a mix

of drive types, as it would be difficult to determine which drive

type was plugged in to which port. I was able to determine

that the problem was with the drive firmware version and

upgraded all the drives that exhibited this behavior.

As the system already was in active use before I deter-

mined that the firmware was the issue, I needed a way to

upgrade each drive while keeping the system running. I could

not simply upgrade the drives while they were part of an

active disk array, as Seagate claims the upgrade could destroy

data. I used the 3ware interface to remove the problem drive,

which then forced the hot spare to replace it. The RAID con-

troller automatically started to rebuild the RAID 5 array using

the hot spare. I then physically removed the drive from the

chassis and upgraded the drive firmware using another com-

puter. After the upgrade, I re-inserted the drive and desig-

nated it as the new hot spare. The array rebuild operation

took something like six hours to complete, and as I could

remove and upgrade only one drive at a time, I was limited

to one drive upgrade a day.

Conclusion

I have been using this system in production for several months

and have consumed only a fraction of the available space:

# df -t xfs

Filesystem 1K-blocks Used Available Use% Mounted on

/dev/sdb1 13566738304 2245371020 11321367284 17% /backup

I am quite happy with the result, as I have plenty of room

to add more systems to the backup schedule, and I am confi-

dent I will not lose any backups due to hardware failures.

Eric Pearce is the IT Lead for AmberPoint, Inc, an SOA governance software company based in

Oakland, California. He has authored several books on UNIX and Windows system administration

for O’Reilly & Associates.

The script command is used to log an entire session. Type the

command

script

at the command prompt, and script then copies

everything you type and its response to the file typescript. Script

starts a sub-shell; when you want to stop saving the session, end

the sub-shell (normally with Ctrl-D or by typing

exit

A very useful feature of the script command is that it can

output timing information to a separate file. The script and

the timing information then can be used to replay the script.

The following example creates a script and timing data

(timing data is always written to standard error):

$ script -t 2> timinginfo

Script started, file is typescript

$ ls

Desktop test scripts redbooks

$ pwd

/home/jagadish

$ hostname

homepc

$ exit

exit

Script done, file is typescript

The entire terminal session then can be replayed later (with

exact timing) using the

scriptreplay

command:

$ scriptreplay timinginfo

$ ls

Desktop test scripts redbooks

$ pwd

/home/jagadish

$ hostname

homepc

$ exit

exit

Script is a useful tool for training and educational purposes.

—JAGADISH KAVUTURU

TECH TIP

Capture and Play Back Your Session