Re: raid0 low performance

[Ming Zhang <mingz@ele.uri.edu>]

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i also suspect this marvel driver or chip and want to change to another
one. but before buying one, maybe i should gather some information on
which one is the best 8port or 12 port. :P

cpu utilization is not high. < 20%

i write a small program that allocate a piece of buffer and write the
buffer to device again and again synchronously, no mmap, glibc fwrite,
just basic write system call. i can attach the code here if this list
allows.

i tested to write to /dev/null or a ram disk, pretty fast.

ming


On Thu, 2005-06-30 at 19:28 -0700, Tyler wrote:
> My guess at a glance would be either the Marvel driver is at fault, or 
> the simple fact of software raid performance... did you monitor the cpu 
> useage during the tests?  even PCI 32bit, 33mhz should be able to hit 
> 133 Mbytes per second I believe.  What are you writing *from* ? dev/zero 
> or another drive that may not have a read speed high enough to keep up 
> with what is available?
> 
> Tyler.
> 
> Ming Zhang wrote:
> 
> >I meet some strange low performance when run RAID0 with vanilla kernel
> >2.4.27/2.6.11.12.
> >
> >My box is a 2.8G P4 and 1G RAM. 8 400GB SATA disk and A marvel 8port
> >controller. I run marvel 3.4.1 driver. I wrote a small program to write
> >device sequentially and SYNCHRONOUSLY.
> >
> >This is performance of 1 disk. looks fine.
> >
> > 1048576Bytes *     1024 :    55.466MB/s
> >  524288Bytes *     2048 :    55.830MB/s
> >  262144Bytes *     4096 :    55.782MB/s
> >  131072Bytes *     8192 :    55.567MB/s
> >   65536Bytes *    16384 :    55.926MB/s
> >   32768Bytes *    32768 :    54.344MB/s
> >   16384Bytes *    65536 :    41.415MB/s
> >    8192Bytes *    65536 :    26.499MB/s
> >    4096Bytes *    65536 :    15.110MB/s
> >    2048Bytes *    65536 :     8.422MB/s
> >    1024Bytes *    65536 :     4.318MB/s
> >
> >But when run 2 disk raid0, there is only 10% improvement.
> >
> >md3 : active raid0 sdb[1] sda[0]
> >      781422592 blocks 64k chunks
> > 1048576Bytes *     1024 :    67.300MB/s
> >  524288Bytes *     2048 :    66.796MB/s
> >  262144Bytes *     4096 :    65.728MB/s
> >  131072Bytes *     8192 :    65.017MB/s
> >   65536Bytes *    16384 :    59.223MB/s
> >   32768Bytes *    32768 :    49.766MB/s
> >   16384Bytes *    65536 :    39.162MB/s
> >    8192Bytes *    65536 :    26.386MB/s
> >    4096Bytes *    65536 :    15.084MB/s
> >    2048Bytes *    65536 :     8.383MB/s
> >    1024Bytes *    65536 :     4.303MB/s
> >
> >And when use 4 disks, the speed is slower!
> >md0 : active raid0 sdh[3] sdg[2] sdf[1] sde[0]
> >      1562845184 blocks 64k chunks
> > 1048576Bytes *     1024 :    58.032MB/s
> >  524288Bytes *     2048 :    56.994MB/s
> >  262144Bytes *     4096 :    58.289MB/s
> >  131072Bytes *     8192 :    65.999MB/s
> >   65536Bytes *    16384 :    59.723MB/s
> >   32768Bytes *    32768 :    50.061MB/s
> >   16384Bytes *    65536 :    38.689MB/s
> >    8192Bytes *    65536 :    26.169MB/s
> >    4096Bytes *    65536 :    15.169MB/s
> >    2048Bytes *    65536 :     8.378MB/s
> >    1024Bytes *    65536 :     4.287MB/s
> >
> >
> >Any hint on this?
> >
> >* I do not know how to check current PCI bus speed and I am not sure
> >whether is limited by that. It is a 64bit card but I am not sure if it
> >is run at 66MHZ. Should be, but want to check to make sure.
> >* I tested each disk and all disk performs OK.
> >
> >
> >Thanks
> >
> >
> >Ming
> >
> >  
> >
> 

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