raid question

[jshankar <jshankar@CS.ColoState.EDU>]

Hello,

I have couple of questions regarding raid routine.

1> When i do mkraid, is there any specific routines in md.c that is 
responsible for adding and tracking the device. I have maintain the entries in 
/etc/raidtab. When i copy a file into the raid device, is there any specific 
routine that track  the  device to write the next block( raid 0  case).

2> Also the routine that  keeps track the amount
of buffer size that can be written to each particular device and the case when
the writing to one disk fails.



3> Also i was  wondering whether the source code of raid tools are availaible 
in
linux directory.

It would be great if somebody  can throw some light.

Thanks in advance.


-Jay



>===== Original Message From Neil Brown <neilb@cse.unsw.edu.au> =====
>On Wednesday July 30, jshankar@CS.ColoState.EDU wrote:
>> Hello ,
>>
>> I am Jayshankar, Masters student in Colorado State UNiversity.
>>
>> A small question on raid.
>>
>> Suppose i have got raid0 connected to disk1, disk2 , disk3 , disk4.
>>
>> The operating system writes a block of data to disk1 then to disk2, disk3,
>> disk4. Do the I/O needs to be successful on disk1, for writing the next
block
>> of data on disk2, disk3, disk4. Or it checks the I/O is successful on
disk1,
>> after the block of data has been written to disk2,disk3,disk4.
>>
>>
>> Looking forward for your reply.
>>
>> THanks in advance.
>>
>> -Jay
>
>Please send future questions to
>  linux-raid@vger.kernel.org
>rather than to me personally.
>
>All disk IO in Linux is asynchronous.
>i.e. submitting a block schedules it for IO.  If you submit lots of
>blocks they all get scheduled for IO.  This is true whether your are
>accessing a single device or a raid array.
>
>So there is no check for success of one block before writing the
>next.  quite often the blocks writen to the different drive will all
>be written at one.
>
>NeilBrown