Hi
The lower performance remains to the bandwidth of the IDE controller. I
think it is one of the older controllers / chipsets, which are only able
to put round about 16 MB/s through.
If you have both drives on one controller (master/slave) the datastream
will be limited to 16 MB/s wether they are striped, mirrored or
whatever.
The fact using raid1 leads to the explanation that the cpu is loaded
higher by reading or writing from/onto two disks same time (raid1).
Also both disks will not be identical, wether they are of the same
manufacturer and model or not; and you will loose some performance by
syncing the disks (the controller has to wait for the writes (reads) of
both disks, before it will go on).
Readperformance will only increase by using raid0 (stripe), but it will
not be twice times faster.
Greetings, Dietmar
Joachim Zobel wrote:
>
> Hi,
>
> I`m running raidtools-0.41 on a P75. I'm using raid1 because I know there
> will be a day when one of my disks will fail. There are three ide disks and
> a cdrom.
>
> Running hdparm on md0 and its components gives me:
>
> dilbert:/root # hdparm -tT /dev/hdd1 /dev/hda6 /dev/md0
>
> /dev/hdd1:
> Timing buffer-cache reads: 64 MB in 3.76 seconds =17.02 MB/sec
> Timing buffered disk reads: 32 MB in 11.64 seconds = 2.75 MB/sec
>
> /dev/hda6:
> Timing buffer-cache reads: 64 MB in 3.78 seconds =16.93 MB/sec
> Timing buffered disk reads: 32 MB in 10.55 seconds = 3.03 MB/sec
>
> /dev/md0:
> Timing buffer-cache reads: 64 MB in 4.03 seconds =15.88 MB/sec
> Timing buffered disk reads: 32 MB in 15.11 seconds = 2.12 MB/sec
>
> Why is this?
> Any hints?
>
> Thanx,
> Joachim
>
> --
> "... ein Geschlecht erfinderischer Zwerge, die fuer alles gemietet werden
> koennen." - Bertolt Brecht - Leben des Galilei
--
"For those about to rock - we salute you!"
Dietmar Stein, Systemadministrator UNIX/Linux
http://home.t-online.de/home/dstein2203
[EMAIL PROTECTED], [EMAIL PROTECTED]
