Re: Poor raid 1 performance?

Peter wrote:

> It is organized very differently. There are NO STRIPES in RAID1. On each
> disk data seem to be organized exactly the same as on standalone hard drive.

Of course there are no RAID0 stripes in RAID1. But for reading, a stripe is
nothing more than a subset of data. In RAID1, /all/ the data is there, so
the controller can make up, on the fly, as needed, its own "virtual
stripes"; meaning, it can read whatever data it needs to read from disk A
and read whatever data it needs to read from disk B, in that sense read one
"virtual stripe" from disk A and another "virtual stripe" from disk B. The
data is there, on both disks, and parts of it can be read from one disk,
other parts from the other disk. (I just called those parts "virtual
stripes", indicating that they are not real stripes.)

Just lay out in front of you how the data of a certain file is organized in
RAID0, and what the controller does to speed up the reading. Now lay out in
front of you how that same file data is organized in RAID1, and apply the
same technique to speed up the reading. Seems perfectly possible, even
though RAID1 doesn't have explicit stripes.

You may want to go back and read what I wrote... :)

Gerhard
.

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