On Wed, Feb 28, 2001 at 03:58:11PM +0100, Martin Rauh wrote:
>
> Writing to an software RAID 0 containing 4 SCSI discs is very fast.
> I get transfer rates of about 100 MBytes/s. The filesystem on the RAID
> is ext2.
>
> Writing to the same RAID directly (that means on the raw device without
> a filesystem) works
> but gives low transfer rates of about 31 MBytes/s.
>
> Any explanation for that?
Raw IO is always synchronous: it gets flushed to disk before the write
returns. You don't get any write-behind with raw IO, so the smaller
the blocksize you write in, the slower things get.
--Stephen
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