Archive for December, 2006

Shall we buy Seagate stock now?

HD DVD’s AACS protection has been compromised base on this news. It is amazing that big giants wasted quite a lot of $$$ (millions of $, I bet) again just because of 8-day hacker’s work. Considering how many people will backup how many HD movies into their hard drives, and considering the huge space a HD movie will take, there is not reason not to buy some Seagate (or other hard drive companies) stocks… ;)

What a new year gift!

Update: Blu-ray is cracked as well…

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blktrace is a tool developed by Jens Axboe to trace the Linux io request. Here is a nice blktrace guide about installation and use. I have a live example to show why blktrace is useful.

Andre post a new io mode, blockio, for IET last month. The code runs well for him with various Linux iSCSI initiator. Later Ross found one problem with it. A Windows host can not create file system on any iSCSI volume export with blockio mode while Linux host can. And more funny thing is once a NTFS or FAT32 partition is created in advanced on an iSCSI volume, the Windows host can recognize the file system and do various file system operation without problem.

So what is the problem?

We used Wireshark to get all the iSCSI traffic. Windows format will read immediately after a write and the data read out is not the same as previous write. This confused the Window and lead to failure. But why normal I/O after format can read correct data out? We need a way to find out what happened exactly in various Linux IO layers. blktrace shines here.

We reran the format with blktrace running. Here is what we got.


8,16 0 768 7.012762981 4916 Q W 6736 + 32 [istiod1]
8,16 0 769 7.012766958 4916 G W 6736 + 32 [istiod1]
8,16 0 770 7.012769506 4916 P R [istiod1]
8,16 0 771 7.012770511 4916 I W 6736 + 32 [istiod1]
8,16 0 772 7.012777259 4916 D W 6736 + 32 [istiod1]
8,16 0 773 7.012981610 4916 C W 6736 + 32 [0]
8,16 0 774 7.013543284 4916 Q R 6736 + 32 [istiod1]
8,16 0 775 7.013546301 4916 G R 6736 + 32 [istiod1]
8,16 0 776 7.013548430 4916 P R [istiod1]
8,16 0 777 7.013549233 4916 I R 6736 + 32 [istiod1]
8,16 0 778 7.014866251 0 UT R [swapper] 1
8,16 0 779 7.014880793 9 U R [kblockd/0] 1
8,16 0 780 7.014885958 9 D R 6736 + 32 [kblockd/0]
8,16 0 781 7.015813374 9 C R 6736 + 32 [0]

Till now it looks ok.
8,16 0 782 7.025277381 4915 Q W 6768 + 32 [istiod1]
8,16 0 783 7.025283850 4915 G W 6768 + 32 [istiod1]
8,16 0 784 7.025286799 4915 P R [istiod1]
8,16 0 785 7.025287794 4915 I W 6768 + 32 [istiod1]

A new write (W) request was inserted (Q) into the queue.

8,16 0 786 7.026059876 4915 Q R 6768 + 32 [istiod1]
8,16 0 787 7.026064451 4915 G R 6768 + 32 [istiod1]
8,16 0 788 7.026066369 4915 I R 6768 + 32 [istiod1]

Before we see the write request finishes, a new read (R) request was also inserted (Q) into the queue.

8,16 0 789 7.034883766 0 UT R [swapper] 2
8,16 0 790 7.034904284 9 U R [kblockd/0] 2

The block device IO queue was unplugged.
8,16 0 791 7.045272094 9 D R 6768 + 32 [kblockd/0]
8,16 0 792 7.045654039 9 C R 6768 + 32 [0]

Bingo! Here the read request was sent to device and finished before write.

8,16 0 793 7.045669809 9 D W 6768 + 32 [kblockd/0]
8,16 0 794 7.049840970 0 C W 6768 + 32 [0]

Repeat Linux mkfs and do not see such IO pattern. So because Windows and Linux do I/O differently during creating file system, such error does not show up in Linux. And since read the same block from last write request (especially bypass the initiator file system cache and send to storage directly) is so rare that we do not see error in normal I/O.

The root reason is because that version of blockio does not preserve the I/O order in all time. Andre, Ross, and I are working on that.

So with a tool that can tell you what precisely happen, life is much easier!

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SNIA dictionary

It is quite easy to misunderstand each other if people do not use a common terminology. At least we had quite a hard time when we misunderstood the “stripe size” in IET mailing list. So this A Dictionary of Storage Networking Terminology from SNIA should be useful. It is not an easy read. But what the hell you want to read a dictionary? ;) Look up when you need.

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Your Linux boot very slow? Try bootchart. It is “a tool for performance analysis and visualization of the GNU/Linux boot process. Resource utilization and process information are collected during the boot process and are later rendered in a PNG, SVG or EPS encoded chart.”

When developing the Linux based appliance, we always want to squeeze the boot time to give user a better experience (over-engineering? ;)). This tool will shine there.

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2007 is coming

2007 is coming to everyone, or already came to my family and friends in China. Like everybody else, I wish we all can have a great 2007, a healthy 2007, and a wealthy 2007.

No pay, no gain. When I think about what I will get in 2007, I should begin to plan what I will pay in 2007, right? :)

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About tape encryption

IBM Redbook released a nice solution guide about its TS1120. Chapter 3 is a nice read and gives you an idea about tape encryption. Regarding others chapters, I am not sure since I can not afford a TS1120 in my home office. Maybe you can?

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TCP/IP Tutorial and Technical Overview

IBM Redbooks just released a nice book about TCP/IP. If you have no money to buy other books about TCP/IP, this is a good free one for you. ;) I have a quick read and need to squeeze more time to spend on it.

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Where is the snow?

No snow this winter so far in MA, guess we can not see more before 2007. So where it is? Or one day no snow any more with more and more snap? BTW, there is people who noticed another kind of warming.

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Put Windows into your next car?!

Read this news that “Ford Motor Co. and software giant Microsoft Corp. are expected to jointly announce soon that new Windows Automotive software soon will be available in Ford vehicles.”

Of course my next car will not be a Ford one. I am never a fan of Ford. But if other Auto makers also do this, I wonder if I can save some $$$ by asking the dealer give me a Linux version?

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Tuning os for high speed network transfer

Yesterday Ross send me a link about tuning OS for high speed network transfer. Thank you!

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