Thread (28 messages) 28 messages, 11 authors, 2007-03-13

Re: impact of 4k sector size on the IO & FS stack

From: Ric Wheeler <hidden>
Date: 2007-03-12 02:41:59
Also in: linux-fsdevel, linux-scsi

Alan Cox wrote:
quoted
Are there other concerns in the IO or FS stack that we should bring up 
with vendors?  I have been asked to summarize the impact of 4k sectors 
on linux  for a disk vendor gathering and want to make sure that I put 
all of our linux specific items into that summary...
    
We need to make sure the physical sector size is correctly reported by
the disk (eg in the ATA7 identify data) but I think for libata at least
the right bits are already there and we've got a fair amount of scsi disk
experience with other media sizes (eg 2K) already. 256byte/sector media
is still broken btw 8)
  
It would be really interesting to see if we can validate this with 
prototype drives.
I would be interested to know what the disk vendors intend to use as
their strategy when (with ATA) they have a 512 byte write from an older
file system/setup into a 4K block. The case where errors magically appear
in other parts of the fs when such an error occurs are not IMHO too well
considered.

Alan
As Jeff mentioned, I think that they would have to do a 
read-modify-write simulation which would kill performance for a small, 
random write work load...

ric
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