If "necessity is the mother of invention", then I think laziness is
the father :-)
> btw what does this message in boot.msg mean?
> <4>raid5: switching cache buffer size, 4096 --> 1024
> <4>raid5: switching cache buffer size, 1024 --> 4096
The raid5 module maintains a stripe cache. The width of this cache
needs to be the same as the size of requests that are received.
The initial default size if 4096.
When you mkfs or fsck, the I/O requests that arrive are 1024 bytes
long, so the cache is flushed and rebuilt with a different size.
After you mount a filesystem, requests start coming at filesystem
blocksize, which is typically 4096 bytes.
If you happen to use LVM to partition a raid5 device, and have a
1K-block filesystem in one partition and a 4k-block filesystem in
another, then requests of different sizes will arrived mixed together
and the stripe cache will constantly be flushed and rebuilt and you
will gets lots of these messages together with a performance hit as
lots of requests will get serialised by the cache flushing.
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