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Re: Limited write bandwidth from ext3



On Jun 19, 2006  14:18 -0400, Sinha_Himanshu emc com wrote:
> We measured the write bandwidth for writes to the block device
> corresponding to the lun (e.g. /dev/sdb), a file in an ext2 filesystem
> and to a file in an ext3 file system.
> 		Write b/w for 512 KB writes
> Block device	312 MBps
> Ext2 file		247 MBps
> Ext3 file		130 MBps
> 
> We are looking for ways to improve the ext3 file write bandwidth.

Have a look at the extents+mballoc+delalloc patches from Alex Tomas:

ftp://ftp.lustre.org/pub/people/alex/2.6.16.8/

Mount the filesystem with "-o extents,mballoc,delalloc" to enable this.

They noticably improve IO performance while also reducing the CPU load
for ext3.  The extent patches are approved by all of the ext3 developers
and will be supported upstream fairly soon (in the kernel and e2fsprogs),
and mballoc+delalloc will follow on afterward.

NOTE: the extents on-disk format is incompatible with older kernels, so
      at this stage consider it "for benchmarking only".

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.


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