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SubjectRe: [reiserfs-list] ReiserFS on RAID5 Linux-2.4 - speed problem
Thanks for the reply!

On Thu, 29 Nov 2001 17:11:51 +0000
Edward Shushkin <> wrote:

> Thats odd!
> I don't have three various ide-controllers to reproduce your configuration,

You only need one controller in additoin to your on-board one ... 2x 2 channels
-> 4 IDE Master possible ...

> but for the raid5 of 3 various scsi disks i have that the times of dd readings for
> if= /dev/sda, /dev/md0, /mnt/file_on_reiserfs_on_md0 relates approximately as
> 1.5 : 1 : 1
> So the performance doesn't decrease..
> What is about your speed for (dd if=/dev/hdx...)??

Hardware: AMD K6-2 350Mhz; 128MB RAM; Aladin5 based Gigabyte board; additinal
Promise ULTRA ATA-100 controller; vanilla 2.4.16 kernel; [glibc-2.1.3]

I tuned the kernel a bit by:
echo 1023 > /proc/sys/vm/max-readahead
(without this some short test were much worser ...)

RAID-disk I RAID-disk II RAID-disk III
host2 ch0 ma host2 ch1 ma host0 ch1 ma
1. hdparm -tT
60.66 MB/sec 60.66 MB/sec 60.66 MB/sec
20.13 MB/sec 23.62 MB/sec 15.92 MB/sec (UDMA mode II only)

2. dd if=x of=/dev/null bs=1024 count=100000 (avg. of 3 measurements)
30.52 MB/sec 30.54 MB/sec 30.6 MB/sec (??? UDMA2 ... ?)
# ok too much is cached by LInux ... again with 400 MB:

3. dd if=x of=/dev/null bs=1024 count=400000 (avg. of 3 measurements)
30.92 MB/sec 28.32 MB/sec 29.32 MB/sec

4. time dd if=/dev/md/0 of=/dev/null bs=1024 count=400000 (avg. of 3 measurements)
34.567 MB/sec

4. time dd if=/home/everybody/video/movies/Matrix\ 1-2.avi of=/dev/null bs=1024 count=200000
(home is the ReiserFS on RAID5 filesystem ...) (avg. of 3 measurements)
8.785 MB/sec

5. time dd if=/home/everybody/video/movies/Matrix\ 1-2.avi of=/dev/null bs=1024 count=400000
(home is the ReiserFS on RAID5 filesystem ...) (avg. of 3 measurements)
9.306 MB/ses

So I have ide/discX md/0 file-from-reiserfs:
3.2 : 3.71 : 1

Over NFS I get 7.1 MB/sec - this is MUCH better than yesterday - so the "echo 1023 >
/proc/sys/vm/max-readahead" must have done it ... - but more would still be better ;-)
(I'll write a benchmark script and redo the test without this tuning tonight ...)

1. The uncontinous results may be caused by a compile workstation that currently compiles
my distribution and accesed some source from time to time (not that much ...).

2. I allready "tuned" the IDE by the additional IDE controller. At the beginning
all discs were connected to the on-board Ali - which gave much worser results. So I added
the Promisse one so that each disc is a Master without Slave devices (I thought the
slowdown may be caused by the concurrend IDE-bus accesses ...)

Question: Are there some block-sizes / allignments issues I should take care when using
ReiserFS on RAID5 ?? - The current setup is a straightforward first-try with default
parameters for all tools (mkraid / mkreiserfs ... - I found no hints on the web).

> Can you measure this for ext2 on md0?

No - sorry. It is a "production" machine. I could backup all the stuff and reinitialize
RAID and reiserfs in another way when I know what to do better (except using SCSI ;-)
or what I did wrong - but I can not play arround with the data all the time ...

> Thanks,
> Edward.

k33p h4ck1n6

René Rebe (Registered Linux user: #127875 <>)



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