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raid0 and iscsi

DISCUSSION jshankar 1 participant 1 message Oct 13, 2003 MD RAID

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jshankar

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Hello Neil/Rob,

I am using IP based network(2 Intel Ethernet card Pro 1000/T). CPUinfo is as below
:

processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 8
model name : Pentium III (Coppermine)
stepping : 1
cpu MHz : 526.186
cache size : 256 KB
fdiv_bug : no
hlt_bug : no
f00f_bug : no
coma_bug : no
fpu : yes
fpu_exception : yes
cpuid level : 2
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
cmov
pat pse36 mmx fxsr sse
bogomips : 1044.22

Can u please explain me about the below fuctionality:
2>If my chunk size is 8 byte. Does that mean it will write 8 byte into device 0
and then into device 1. Is the write request to the disk in synchronous or asynchronous mode.

3> Is wite_disk_sb in md.c responsible for writing into disk??. Is fsync_dev responsible for synhronous write ??. If so can i change to asynchronous write.I
will really appreciate if somebody can tell me what all routines I need to go through to figure out the functionality of raid0 behaviourand how it write to disk.

Thanks
Jay

===== Original Message From rob <[email protected]> =====

Quoted 84 lines

Hello,
What kind of network are you uasing for the data transfer?

The rest of post does not answer your specific questions, but is to show the transfer speeds on our network to backup servers using hardware and software raid.

Both systems use Mandrake 9.1. network is a fast-lan. speed 100.

Bkup1 is scsi with Mylex hardware raid, athlon 1800 cpu. array has 4 9-gb lvd disks.

Bkup2 is a new test server using software raid. dual 750 intel xeon, 4- 9-gb se scsi disks.

I transfer data 30-40 times per day to each server. 500-mb hourly on the average. ususal tme is less than a min.
The test uses rsync to transfer data. rsync uses a lot of cpu so the speed difference may be more due to cpu than the difference of raid type.

the command used: rsync -e ssh -a --stats /bkup3/ fbc5:/bkup3/

here is the result of sending approx 3-gb of data to each:

-------------------------------------------------
this is the output of an rsync transfer to the backup software-raid server:

Mon Oct 13 07:36:41 EDT 2003
rsync[21832] (sender) heap statistics:
arena: 7996056 (bytes from sbrk)
ordblks: 59 (chunks not in use)
smblks: 2
hblks: 1 (chunks from mmap)
hblkhd: 516096 (bytes from mmap)
usmblks: 0
fsmblks: 80

 uordblks:     7821736   (bytes used)
 fordblks:      174320   (bytes free)
 keepcost:      128840   (bytes in releasable chunk)

Number of files: 65699
Number of files transferred: 45739
Total file size: 2707740663 bytes
Total transferred file size: 2707630760 bytes
Literal data: 2707630760 bytes
Matched data: 0 bytes
File list size: 1,925,417
Total bytes written: 2,711,680,565
Total bytes read: 731844

wrote 2711680565 bytes read 731844 bytes 5,046,348.67 bytes/sec total size is 2707740663 speedup is 1.00
Mon Oct 13 07:45:38 EDT 2003

------------------------------------
to the hardware raid server:
Mon Oct 13 07:23:19 EDT 2003
rsync[19963] (sender) heap statistics:
arena: 7996056 (bytes from sbrk)
ordblks: 59 (chunks not in use)
smblks: 2
hblks: 1 (chunks from mmap)
hblkhd: 516096 (bytes from mmap)
usmblks: 0
fsmblks: 80

 uordblks:     7821736   (bytes used)
 fordblks:      174320   (bytes free)
 keepcost:      128840   (bytes in releasable chunk)

Number of files: 65699
Number of files transferred: 45739
Total file size: 2707740663 bytes
Total transferred file size: 2707630760 bytes
Literal data: 2707630760 bytes
Matched data: 0 bytes
File list size: 1925417
Total bytes written: 2,711,680,565
Total bytes read: 731844

wrote 2711680565 bytes read 731844 bytes 8,384,582.41 bytes/sec total size is 2707740663 speedup is 1.00
Mon Oct 13 07:28:42 EDT 2003

Quoted 14 lines

----------------

Quoted 8 lines · Jayshankar Nair

Hello,

I was testing the raid0 configuration for the iscsi device ( /dev/sdb and /dev/sdc).

For writing a 512MB in a LAN environment it was taking 24 hrs. i was going through the source code of raid0.c and certain things doesn't made sense to

me.

Quoted 3 lines
Quoted 3 lines

1> what role does the Hash bit play.
2>If my chunk size is 8 byte. Does that mean it will write 8 byte into

device 0

Quoted 6 lines
Quoted 6 lines

and then into device 1. Is the write request to the disk in synchronous or asynchronous mode.

3> Is wite_disk_sb in md.c responsible for writing into disk??. Is fsync_dev responsible for synhronous write ??. If so can i change to asynchronous

write.I

Quoted 1 line
Quoted 1 line

will really appreciate if somebody can tell me what all routines I need to

go

Quoted 16 lines
Quoted 11 lines

through to figure out the functionality of raid0 behaviour.

Thanks
Jayshankar

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