Linux drivers for ICH5R (RAID1) and Promise PDC20378, Performance

Linux drivers for ICH5R (RAID1) and Promise PDC20378, Performance

[Hermann Himmelbauer]

Hi,
I am considering buying a new Intel based Motherboard (875P chipset) with 2 
RAID-Controller on Board: ICH5R and Promise PDC20378.

I want to know if the RAID1 functionality of Intel's 875P Southbridge (ICH5R) 
is fully supported by Linux. I read that at the launch of the ICH5R only 
RAID0 was supported but by a BIOS update, RAID1 is now also available. Is the 
driver (if there is any) pre-alpha or has it somehow proved to be stable?

Moreover I want to know if there are drivers for the Promise PDC20378.

But here's another question: Let's assume those 2 RAID chips are perfectly 
supported by Linux and you would want to set up a fast RAID1 solution with 
e.g. 2* WD-Raptor SATA disks. There are 3 ways to do this:

1) Software RAID: Easy, no driver support needed, but would this be very CPU 
intensive? Moreover is grub already capable to load the kernel from a RAID1 
device? Another disadvantage would be that during write operations the 
traffic between the CPU and the disk subsystem is doubled compared to a 
HW-RAID solution.

2) HW RAID with ICH5R: This variant has the advantage that the SATA-channels 
are directly connected to the Chipset and do not stress the PCI-bus.

3) HW RAID with Promise

Theoretically the read speed of a RAID1 device should be double of a single 
disk. Anyway it seems that currently available HW-RAID1 solutions are even 
slower than a single disk. What would this be like with Linux SW-RAID? Would 
SW-RAID double the read-speed?

What would you prefer?

Moreover I would like to know which filesystem would suit best. For the 
HW-RAID solutions this should not make any difference but I heard that e.g. 
ReiserFS + Linux SW-RAID is quite slow.

		Best Regards,
		Hermann

-- 
x1@aon.at
GPG key ID: 299893C7 (on keyservers)
FP: 0124 2584 8809 EF2A DBF9  4902 64B4 D16B 2998 93C7

Re: Linux drivers for ICH5R (RAID1) and Promise PDC20378, Performance

[Steven Dake]

On Mon, 2003-10-13 at 15:08, Hermann Himmelbauer wrote:
> Hi,
> I am considering buying a new Intel based Motherboard (875P chipset) with 2 
> RAID-Controller on Board: ICH5R and Promise PDC20378.
> 
> I want to know if the RAID1 functionality of Intel's 875P Southbridge (ICH5R) 
> is fully supported by Linux. I read that at the launch of the ICH5R only 
> RAID0 was supported but by a BIOS update, RAID1 is now also available. Is the 
> driver (if there is any) pre-alpha or has it somehow proved to be stable?
> 
> Moreover I want to know if there are drivers for the Promise PDC20378.
> 
> But here's another question: Let's assume those 2 RAID chips are perfectly 
> supported by Linux and you would want to set up a fast RAID1 solution with 
> e.g. 2* WD-Raptor SATA disks. There are 3 ways to do this:
> 
> 1) Software RAID: Easy, no driver support needed, but would this be very CPU 
> intensive? Moreover is grub already capable to load the kernel from a RAID1 
> device? Another disadvantage would be that during write operations the 
> traffic between the CPU and the disk subsystem is doubled compared to a 
> HW-RAID solution.
> 
> 2) HW RAID with ICH5R: This variant has the advantage that the SATA-channels 
> are directly connected to the Chipset and do not stress the PCI-bus.
> 
> 3) HW RAID with Promise
> 
> Theoretically the read speed of a RAID1 device should be double of a single 
> disk. Anyway it seems that currently available HW-RAID1 solutions are even 
> slower than a single disk. What would this be like with Linux SW-RAID? Would 
> SW-RAID double the read-speed?
> 
> What would you prefer?
> 
> Moreover I would like to know which filesystem would suit best. For the 
> HW-RAID solutions this should not make any difference but I heard that e.g. 
> ReiserFS + Linux SW-RAID is quite slow.
> 
I use ext3 + raid1 with two western digital 8MB cache disks.  I get
about 65mb/sec sustained read performance.  With one disk, I get about
40mb/sec sustained read performance.  The linux raid code read balances
across disks, but doesn't write balance.

The performance of the ataraid code is worse.  I think it doesn't read
balance, but I'm not sure.  I do know that you probably want to stick
with linux raid, or a real hardware raid controller that doesn't rely on
drivers to concatenate/mirror the devices.

Thanks
-steve
> 		Best Regards,
> 		Hermann

Re: Linux drivers for ICH5R (RAID1) and Promise PDC20378, Performance

[Hermann Himmelbauer]

On Tuesday 14 October 2003 00:15, Steven Dake wrote:
> On Mon, 2003-10-13 at 15:08, Hermann Himmelbauer wrote:
> > Moreover I would like to know which filesystem would suit best. For the
> > HW-RAID solutions this should not make any difference but I heard that
> > e.g. ReiserFS + Linux SW-RAID is quite slow.
>
> I use ext3 + raid1 with two western digital 8MB cache disks.  I get
> about 65mb/sec sustained read performance.  With one disk, I get about
> 40mb/sec sustained read performance.  The linux raid code read balances
> across disks, but doesn't write balance.

Thank you for your quick answer.
This sounds interesting, but what is the CPU Load of your System when 
reading/writing with full speed? (e.g. cat big-file > /dev/null)
I read that the ICH5R and the Promise use only ~ 3% of the CPU.

		Best Regards,
		Hermann

-- 
x1@aon.at
GPG key ID: 299893C7 (on keyservers)
FP: 0124 2584 8809 EF2A DBF9  4902 64B4 D16B 2998 93C7

Re: Linux drivers for ICH5R (RAID1) and Promise PDC20378, Performance

[rob]

fyi,  this is reading from an ide disk, writting to a software raid 
partition:

# time rsync --stats -v sever* /tmp
severn-i386-disc1.iso
severn-i386-disc2.iso
severn-i386-disc3.iso

Number of files: 3
Number of files transferred: 3
Total file size: 1959821312 bytes
Total transferred file size: 1959821312 bytes
Literal data: 1959821312 bytes
Matched data: 0 bytes
File list size: 72
Total bytes written: 1960060740
Total bytes read: 68

wrote 1960060740 bytes  read 68 bytes  13950610.73 bytes/sec
total size is 1959821312  speedup is 1.00

68.19user 80.37system 2:20.26elapsed 105%CPU (0avgtext+0avgdata 
0maxresident)k
0inputs+0outputs (180major+308minor)pagefaults 0swaps
-----------------------------------
here I deleted the files on the ide drive, then cp from software raid 
drive to the ide drive:

root@fbc5:/tmp # time rsync --stats -v sever* /bkup3
severn-i386-disc1.iso
severn-i386-disc2.iso
severn-i386-disc3.iso

Number of files: 3
Number of files transferred: 3
Total file size: 1959821312 bytes
Total transferred file size: 1959821312 bytes
Literal data: 1959821312 bytes
Matched data: 0 bytes
File list size: 72
Total bytes written: 1960060740
Total bytes read: 68

wrote 1960060740 bytes  read 68 bytes  12136599.43 bytes/sec
total size is 1959821312  speedup is 1.00

69.26user 73.34system 2:40.93elapsed 88%CPU (0avgtext+0avgdata 
0maxresident)k
0inputs+0outputs (180major+308minor)pagefaults 0swaps




--------------------------------------
this is a listing of the files used in the above:

root@fbc5:/bkup3 # ls -l sev*
-rw-r--r--    1 rob      pro      658309120 Sep 24 16:08 
severn-i386-disc1.iso
-rw-r--r--    1 rob      pro      668598272 Sep 24 16:10 
severn-i386-disc2.iso
-rw-r--r--    1 rob      pro      632913920 Sep 24 16:12 
severn-i386-disc3.iso

and comments on the speed or cpu usage?

here is info on the cpus... this is an old dell  computer... 

root@fbc5:/bkup3 # cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 7
model name      : Pentium III (Katmai)
stepping        : 3
cpu MHz         : 547.187
cache size      : 512 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        : 1091.17

processor       : 1
vendor_id       : GenuineIntel
cpu family      : 6
model           : 7
model name      : Pentium III (Katmai)
stepping        : 3
cpu MHz         : 547.187
cache size      : 512 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        : 1091.17

root@fbc5:/bkup3 # uname -r
2.4.21-0.25mdksmp










Hermann Himmelbauer wrote:

>reading/writing with full speed? (e.g. cat big-file > /dev/null)
>I read that the ICH5R and the Promise use only ~ 3% of the CPU.
>
>		Best Regards,
>		Hermann
>
>  
>