Mounting a USB stick
Be sure to have the correct fileset(s) installed before inserting your USB stick. The following file-sets are required to access a USB stick:
# lslpp -L devices.usbif.08025002.rte
Fileset Level State Type Description (Uninstaller)
devices.usbif.08025002.rte
7.1.0.15 A F USB Mass Storage Device
Software
# lslpp -L devices.common.IBM.usb.rte
Fileset Level State Type Description (Uninstaller)
devices.common.IBM.usb.rte
7.1.0.15 A F USB System SoftwareInsert the USB stick and run cfgmgr to discover it:
# cfgmgr
Once discovered, you have two devices (the block and raw device):
ls -l *usbms0 cr--r--r-- 1 root system 44, 0 Aug 22 18:59 rusbms0 br--r--r-- 1 root system 44, 0 Aug 22 18:59 usbms0 //usbms0就是AIX6.1及7.1系统中识别到的U盘的设备文件
It is also shown in the devices output:
# lsdev |grep usb usb0 Available USB System Software usbhc0 Available 08-08 USB Host Controller (33103500) usbhc1 Available 08-09 USB Host Controller (33103500) usbhc2 Available 08-0a USB Enhanced Host Controller (3310e000) usbms0 Available 2.1 USB Mass Storage
For AIX 5.3, the first USB device is shown as flashdrive0. //在AIX5.3中是flashdrive0
At this point, I could treat the USB stick as a raw volume and write data to it. However, in this demonstration, I will mount the USB stick as a file system. I feel there is no need to create a log device for this USB mount, since the purpose of a scratch file system is that it is temporary and thus speed is of the essence when transferring data. To create the USB stick file system use the following command:
# mkfs -V jfs2 -o ea=v2 /dev/usbms0 //原理很简单，你要在AIX中挂载U盘，那U盘就必须是AIX所支持的文件系统格式才行，而AIX支持的本地文件系统类型就jfs和jfs2，所以需要将u盘创建为jfs或者jfs2格式的文件系统 mkfs: destroy /dev/usbms0 (yes)? File system created successfully. 3927736 kilobytes total disk space. Device /dev/usbms0: Standard empty filesystem Size: 7855472 512-byte (DEVBLKSIZE) blocks
The previous command initialized the USB stick. Select "Yes" to destroy, or rather initialize, the device. The file system type is of jfs2 type. I do not believe that a type of jfs2 really matters for this task, as the file system is not going to use the jfs2 log device. But as this is the norm when creating file systems, I created it as a jfs2. To ensure the file system is scalable, I specify that with the 'ea' option. In this example, the device to use is the USB stick inserted, which is usbms0.
For AIX 5.3, there is no NOLOG option in the mount command.
//在AIX5.3中是有-o nolog的参数可以指定的
Next, mount the file system specifying that is it to be mounted without a log device; be sure to create the directory it is to be mounted on first:
# mkdir /usb_mnt # mount -o log=NULL /dev/usbms0 /usb_mnt //挂载的时候需要指定log卷，或者指定log卷为NULL，也就是不指定log卷 # df -g |grep usb /dev/usbms0 3.75 3.73 1% 4 1% /usb_mnt
If you wish to use a log device to mount the usb stick, use the inline log. This ensures that it is contained within the file system:
# mkfs -olog=INLINE,ea=v2 -Vjfs2 /dev/usbms0 //另一种就是在创建jfs2的时候指定log卷为INLINE模式，推荐这种模式，因为我们曾经用Ｕ盘向无法启动的系统中拷贝东西，因为没有创建为INLINE日志卷模式，而导致在光盘启动的维护模式下无法挂载。 mkfs: destroy /dev/usbms0 (yes)? logform: Format inline log for ?y File system created successfully. 3912376 kilobytes total disk space. Device /dev/usbms0: Standard empty filesystem Size: 7824752 512-byte (DEVBLKSIZE) blocks # mkdir /usb_mnt # mount -V jfs2 -o log=/dev/usbms0 /dev/usbms0 /usb_mnt
Unmounting a memory stick
Once you have finished using the a USB stick file system, unmount it, remove it, then delete the usbms0 device:
# umount /usb_mnt # rmdev -dl usbms0
Data on the stick
In this demonstration, I am using a CSV text file called plaks.txt. It is an extract from a database, partial contents of the file is shown below:
alpha,uk01w,12001,jan,-2 bravo,ge01w,98801,jan,-3 charlie,se01w,98111,jan,0 delta,my01w,18811,jan,4 echo,sg01w,34131,janq,2
Earlier I suggested that reading from a USB stick is quick but writing to the USB stick is slower compared to internal disks. This can be somewhat verified by doing an example copy. First, I copied a file from the USB stick to an internal disk. Then, I copied the same file from the internal disk back to the USB stick using the timex command to show the timings of the copy commands. Before both copy operations are carried out, the file systems have been unmounted and re-mounted, so that the operation does not use the file system cache and thus does not blur the timings.
First, the file is copied from the USB stick onto an internal disk to the /holding directory, which resides on an internal disk:
# pwd /usb_mnt # timex cp plaks.txt /holding/ real 0.03
Next, I remove the file from the USB stick and unmount and remount the file systems.
Next, I copied the file back from /holding to the USB stick.
# cd /holding # timex cp plaks.txt /usb_mnt/ real 0.06
The copy of the USB stick takes nearly half the time of the copy from an internal disk. I typically use the USB stick for text extraction. Using awk as an example on data extraction, I extract the pattern 'bravo' contained in the plaks.txt located on the USB stick:
# pwd /usb_mnt # timex awk '/bravo/' plaks.txt real 5.50
Doing the same operation on an internal disk:
# pwd /holding # timex awk '/bravo/' plaks.txt real 8.48
The text extraction is quicker on the stick; in fact, there is a difference of over 3 seconds. Here I am using a relatively small size text file. Though clearly the saving in time is greater when using larger sized exported file, which typically could be up to 8-10MB.
The above, in my opinion, justifies why I choose to use USB sticks for heavy test processing; however, as suggested earlier, if you need to write data you lose out big time. Here I create a 100MB file on the USB stick:
# pwd /usb_mnt # timex lmktemp myfile 100M myfile real 6.60
Next, I do it on an internal disk:
# pwd /holding # timex lmktemp myfile 100M myfile real 1.65
As you can see, there is a difference of over 5 seconds in the writing to a USB stick compared to an internal disk.
USB sticks are great for transferring data when there is no real alternative. I recall one incident, where one of our machines located in a remote region where the SAN disks were failing. These SAN disks contained work flow images. This machine did not have a sturdy network, and we wanted to get these images onto another remote machine for business users to be able to continue to work. The only method quickly available was to buy some 64GB USB sticks, mount them, and tar the images up on the USB sticks. The images were then extracted onto our other AIX box. This method worked with no data loss.
Mounting a previous initialized memory stick
If you are in possession of a memory stick that contains data what was previously mounted as a file system, to access it simply mount it. Be sure to create the mount point first. For example, assume the USB device is inserted in the second USB slot, then have the device discovered as usbms1:
# mkdir /usbstick # mount -o log=NULL /dev/usbms0 /usbstick
Conclusion
Using USB sticks is a great when you want to create a fast read access scratch file system for processing or maybe a raw device to dump some files into for transport to another AIX system. USB sticks offer one solution where you have a poor network, and you need to get a large amount of data transferred.