RE: ext3 file system

jshankar
2003-12-18T04:48:03Z

Hello Hans,

>Filesystems don't usually wait on the IO to complete before submitting
>more IO in response to the next write() syscall. They can do this by
>batching a whole bunch of operations into one committed transaction.
>

Is there a timeout mechanism for batching operations. What if certain
operation
is done after the batch operation is executed. Does it mean that the new
operation has to wait.

Thanks
Jay

>===== Original Message From Hans Reiser <reiser@namesys.com> =====
>jshankar wrote:
>
>>Hello,
>>
>>Please provide some more insight.
>>
>>Suppose a filesystem issues a write command to the disk with around 10 4K
>>Blocks to be written. SCSI device point of view i don't get what is the
>>parallel I/O.
>>It has only 1 write command. If some other sends a write request it needs to
>>be queued. But the next question arises how the write data would be handled.
>>Does it mean the SCSI does not give a response for the block of data
written.
>>In otherwords does it mean that the response would be given after all the
>>block of data is written for a single write request.
>>
>>Thanks
>>Jay
>>
>>
>>
>>
>>
>>
>>>===== Original Message From Mike Fedyk <mfedyk@matchmail.com> =====
>>>On Wed, Dec 17, 2003 at 05:25:49PM -0500, Richard B. Johnson wrote:
>>>
>>>
>>>to the physical media. There are special file-systems (journaling)
>>>that guarantee that something, enough to recover the data, is
>>>written at periodic intervals.
>>>
>>>
>>>Most journaling filesystems make guarantees on the filesystem meta-data,
but
>>>not on the data. Some like ext3, and reiserfs (with suse's journaling
>>>patch) can journal the data, or order things so that the data is written
>>>before any pointers (ie meta-data) make it to the disk so it will be harder
>>>to loose data.
>>>-
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>>
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>>
>>
>>
>In reiser4 we do this more carefully than other filesystems such as
>reiserfs v3, and as a result every fs operation is fully atomic.
>
>--
>Hans
>
>
>-
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