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Re: cpio to ext4 seems much slower than to ext2, ext3 or xfs



On 11/12/2009 03:27 PM, Eric Sandeen wrote:
Roberto Ragusa wrote:
Ric Wheeler wrote:
In our testing with f12, I build a 60TB ext4 file system with 1 billion
small files. A forced fsck of ext4 finished in 2.5 hours give or take a
bit :-) The fill was artificial and the file system was not aged, so
real world results will probably be slower.

fsck time scales mostly with the number of allocated files in my
experience. Allocated blocks (fewer very large files) are quite quick.


What kind of machine did you use?

With 60TB a simple allocation bitmap for 4k-blocks takes almost 2GB;
and this is just to detect free space or double allocation of blocks.
Wow.


The box did have a lot of memory, it's true :)

But ext4 also uses the "uninit_bg" feature:

uninit_bg
   Create  a filesystem without initializing all of the
   block groups.  This feature also  enables  checksums
   and  highest-inode-used  statistics  in  each block-
   group.  This feature can speed  up  filesystem  cre-
   ation   time   noticeably  (if  lazy_itable_init  is
   enabled), and can also reduce e2fsck  time  dramati-
   cally.   It is only supported by the ext4 filesystem
   in recent Linux kernels.

-Eric


A lot in this case was 40GB of DRAM - fsck (iirc) consumed about 13GB of virtual space during the run?

Ric


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