I am trying to understand the use of this parameter. It says that this
is
the size of a continuous chunk of data on one disk. So I guess one would
want to make it small, spreading data accross disks to gain performance
from the striping.
But this does not seem to be the case. A minimal reasonable size of 8k
means than most one block (1k or 4k) requests will come from one disk
with no striping. How dop I get performance when I do randon
(non-sequential)
reads from a file? If i read each block as a number of small (say 512b
sectors)
reads in parallel from a number of disks then I see how I gain.
I must be missing somethging simple here. I did read the doco which not
enough. I checked the list archives but could not do a search. I read
the
last few collections and could not find any related item.
I am now studying the RAID implementation. For starters I attached some
discarded sun disks (6x200MB QUANTUM Model: PD210S SUN0207 Rev: 492S)
and set to measure the results. the disks seem to be slow on their own
(hdparm says 1.36 MB/sec) and I expected some speedup when striped
(raid0). I
got 2.8 MB/sec, just over twice the speed. What gives? I use an ASUS
SC200
SCSI controller, Narrow SCSI, on 2.1.132 with the latest raid patch and
tools.
I played with the chunk size (from a low of 4k to a high of 32k) with no
visible improvement.
--
Eyal Lebedinsky ([EMAIL PROTECTED])
