Re: testing raid 0

["Peter Galbavy" <peter.galbavy@knowtion.net>]

Maybe you have misunderstood the benefit of RAID 0/1/5 etc. RAID 0
givesd you the ability to concatenate disks to get a bigger partition
than would be possible using a single physical device. It will give you
no performance benefits. In fact RAID 0 in RAIDframe is probably rather
inefficient, and you should consider using the simpler ccd(4) drivers.

RAID1 gives you basic mirroring, but at a performance cost and RAID5
gives you parity based protection - at an even higher performance cost.

rgds,
--
Peter Galbavy
Knowtion Ltd.
----- Original Message -----
From: <alx2001@medimex.ro>
To: <misc@openbsd.org>
Sent: Wednesday, August 01, 2001 4:42 PM
Subject: testing raid 0


> Hi,
> I've succesfully configured raid 0 using raidctl on tow hdd (non SCSI;
wd)
> So I went to the next step of testing but I'm disappointed in the
> improvement. Actually it's not an improvement is a loss, I think. Take
a
> look below:
>
> bash-2.05# mount
> /dev/raid0c on /mnt type ffs (local)
>
> bash-2.05# pwd
> /mnt
> bash-2.05# dd if=/dev/zero of=a.file bs=10m count=15
> 15+0 records in
> 15+0 records out
> 157286400 bytes transferred in 20 secs (7864320 bytes/sec)
> bash-2.05# pwd
> /
> bash-2.05# dd if=/dev/zero of=a.file bs=10m count=15
> 15+0 records in
> 15+0 records out
> 157286400 bytes transferred in 9 secs (17476266 bytes/sec)
> bash-2.05#
>
> Hmmm is this a raid ??? or what is it?
>
> Another thing, check this out:
> bash-2.05# iostat 1
>       tty            cd0             wd0             wd1
raid0
> cpu
>  tin tout  KB/t t/s MB/s   KB/t t/s MB/s   KB/t t/s MB/s   KB/t t/s
MB/s
> us ni sy in id
>    1  134  0.00   0 0.00  18.03  12 0.22  15.41   9 0.14  15.25  18
0.27
> 1  0  1  0 98
>   13  268  0.00   0 0.00  29.38 128 3.67  31.18 116 3.53  30.24 244
7.21
> 1  0 16  0 83
>   13   89  0.00   0 0.00  27.16 162 4.31  31.23 144 4.38  29.07 306
8.69
> 0  0
>
> and :
>
> bash-2.05# iostat 1
>       tty            cd0             wd0             wd1
raid0
> cpu
>  tin tout  KB/t t/s MB/s   KB/t t/s MB/s   KB/t t/s MB/s   KB/t t/s
MB/s
> us ni sy in id
>    3   91  0.00   0 0.00  62.54 177 10.82   0.00   0 0.00   0.00   0
0.00
> 2  0 39  6 53
>    0   90  0.00   0 0.00  62.72 271 16.59   0.00   0 0.00   0.00   0
0.00
> 6  0 41  0 53
>    0   90  0.00   0 0.00  62.73 273 16.72   0.00   0 0.00   0.00   0
0.00
> 1  0 31  3 65
>    1   90  0.00   0 0.00  62.06 269 16.29   0.00   0 0.00   0.00   0
0.00
> 0  0 38  3 58
> ....
>
> My raid.conf looks like:
> START array
> 1 2 0
>
> START disks
> /dev/wd0i
> /dev/wd1j
>
> START layout
> 32 1 1 0
>
> START queue
> fifo 100
>
> What can I make to work around this problem. I have openbsd29 current.
> Tks