如果在中需要改变默认的参数如压缩、块大小、缓冲区等，可以使用
smit工具。
具体的方法如下：
1）确定中要修改的设备
# lsdev -Cc tape
smc0 Available 14-08-00-6,0 3583 Library Medium Changer
rmt0 Available 14-08-00-0,0 3580 Ultrium Tape Drive
rmt1 Available 14-08-00-1,0 3580 Ultrium Tape Drive
rmt2 Available 30-68-01 3580 Ultrium Tape Drive (FCP)
smc1 Available 30-68-01 3584 Library Medium Changer (FCP)
rmt3 Available 30-68-01 3580 Ultrium Tape Drive (FCP)
smc2 Available 30-68-01 3584 Library Medium Changer (FCP)
rmt4 Available 30-68-01 3580 Ultrium Tape Drive (FCP)
smc3 Available 30-68-01 3584 Library Medium Changer (FCP)
通过上面的信息我们可以知道系统连接了两个磁带库：
a)用连接的3583，smc0带两个驱动器rmt0,rmt1。
smc0 Available 14-08-00-6,0 3583 Library Medium Changer
rmt0 Available 14-08-00-0,0 3580 Ultrium Tape Drive
rmt1 Available 14-08-00-1,0 3580 Ultrium Tape Drive
b)用光纤连接的3584，三个驱动器各自的control path都被使能。
rmt2 Available 30-68-01 3580 Ultrium Tape Drive (FCP)
smc1 Available 30-68-01 3584 Library Medium Changer (FCP)
rmt3 Available 30-68-01 3580 Ultrium Tape Drive (FCP)
smc2 Available 30-68-01 3584 Library Medium Changer (FCP)
rmt4 Available 30-68-01 3580 Ultrium Tape Drive (FCP)
smc3 Available 30-68-01 3584 Library Medium Changer (FCP)
1.1)假设我们要修改连接的3583上的 ID=2的驱动器的参数：
通过分析我们可以确定rmt1的 ID是1，正是我们要修改的对象。
1.2)假设我们要修改光纤连接的3584上的驱动器的参数：
我们还要通过三个驱动器的WWN来区分他们。首先驱动器的WWN可以
通过驱动器上面的标签得到，然后你可以使用lsattr命令得到WWN和
设备名的对应关系：
#lsattr -El rmt2
block_size 0 Block Size (0=Variable Length) True
compress yes Use Hardware Compression on Tape True
autoload no Use Autoloading Feature at End-of-Tape True
logging no Activate volume information logging True
max_log_size 500 Maximum size of log file (in # of entrIEs) True
space_mode Backward Space/Forward Space Record Mode True
rew_immediate no Use Immediate Bit in Rewind Commands True
trailer_labels no Trailer Label Processing True
retain_reserve no Retain Reservation False
devtype ULT3580- Device Type False
_id 0x213ca Target ID True
lun_id 0x0 Logical Unit Number True
location Location True
ww_name 0x5005076300410803 World Wide Name False
new_name New Logical Name True
1.3)如果驱动器上没有WWN标签，或复杂的环境，或使用FC--GATAWAY
的情况我们可以通过交换机来确定，限于篇幅这里不做介绍。
2）参数：
3.1)显示现有参数的命令：
# lscfg -vl rmt1
DEVICE LOCATION DESCRIPTION
rmt7 30-68-01 3580 Ultrium Tape Drive (FCP)
Manufacturer................
Machine Type and Model......ULT3580-TD1
Serial Number...............6811288675
Device Specific.(FW)........25D4
#lsattr -El rmt2
block_size 0 Block Size (0=Variable Length) True
compress yes Use Hardware Compression on Tape True
autoload no Use Autoloading Feature at End-of-Tape True
logging no Activate volume information logging True
max_log_size 500 Maximum size of log file (in # of entries) True
space_mode Backward Space/Forward Space Record Mode True
rew_immediate no Use Immediate Bit in Rewind Commands True
trailer_labels no Trailer Label Processing True
retain_reserve no Retain Reservation False
devtype ULT3580- Device Type False
_id 0x213ca Target ID True
lun_id 0x0 Logical Unit Number True
location Location True
ww_name 0x5005076300410803 World Wide Name False
new_name New Logical Name True
3.2）设置参数的方法:
我们可以使用SMIT工具修改某一个指定的设备。
具体方法是：
3.2.1)#SMITTY
3.2.2)选择菜单Devices -> Tape Drive -> Change/Show
Characteristics of a Tape Drive.
3.2.3)选择我们指定的设备
3.2.4)修改参数：
Change / Show Characteristics of a Tape Drive
Type or select values in entry fields.
Press Enter AFTER making all desired changes.
[Entry Fields]
Tape Drive rmt0
Tape Drive type 3580
Tape Drive interface
Description 3580 Ultrium Tape
Status Available
Location 14-08-00-0,0
Parent adapter 1
Connection address 0,0
Block Size (0=Variable Length) [0]
Use Hardware Compression on Tape yes
Activate volume information logging no
Maximum size of log file (in # of entries) [500]
Backward Space/Forward Space Record Mode
Use Immediate Bit in Rewind Commands no
Trailer Label Processing no
比如我们可以修改不使用硬件压缩
Use Hardware Compression on Tape no
这种修改是永久生效的。