[ Adding Christoph Lameter to the CC list ]
Hello Ted,
Ted Ts'o wrote:
On Tue, Mar 29, 2011 at 01:52:38PM +0200, Mason wrote:
As far as I can tell from a quick Google search,
there was a push in 2007 to add support for large
blocks in some file-systems, in particular ext2.
e.g. cf. http://lwn.net/Articles/239090/
Was this ever accepted into the main line?
(It seems to have lived within -mm for a while)
Nope, it never was (as you've by now figured out).
I'm working with a ST Microelectronics set-top box.
Here are a few performance results for a 2TB USB HDD:
block size 4k : format = 151 s / mount = 242 s
block size 8k : format = 52 s / mount = 71 s
block size 16k : format = 30 s / mount = 36 s
block size 32k : format = 18 s / mount = 19 s
Using 4kB blocks makes mount too slow on the STB, which
is why I'd like to use larger blocks. It would be nice
if the movies recorded on the STB could also be read on
a Linux PC.
My guess is the mount time slowness is caused an ancient kernel
running on the ST Microelectronics box which is doing mount-time
sanity checks. You can disable this with the mount option -o nocheck.
Unfortunately, the operating system of the set-top box
is not Linux (ST has only very recently started migrating
to Linux).
Their "legacy" OS (OS+ running on top of OS21) provides
(proprietary, I suppose) implementations of FAT32 and ext2.
I used to create FAT32 partitions, until I plugged a 2-TB
USB HDD in the STB:
format = 123 s
mount = 62 s
fsck = 517 s (!!)
I switched to ext2, hoping to avoid the need to fsck, thanks
to the soft updates mode. Problem is, I can't read the files
on a Linux PC if I use large blocks, and performance takes a
dive if I use "normal" blocks.
A lot of the rationale for larger block sizes was obviated by the use
of more advanced file systems, such as ext4, which have other methods
of dealing with the inefficiencies caused by smaller block sizes. If
your main complaint with using a 4k block size on the set-top box was
the mount-time slowness, that can be fixed with the nocheck mount
option.
Unfortunately, the mount function in this OS accepts only
two flags: RDONLY and RDWR :-(
If I understand correctly, I'm screwed, right? :-)
--
Regards.
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