Justin Piszcz wrote:
On Tue, 28 Aug 2007, T. Eichstädt wrote:
Hello all,
thanks for your responses.
Quoting Bill Davidsen <davidsen@xxxxxxx>:
Neil Brown wrote:
On Monday August 27, jpiszcz@xxxxxxxxxxxxxxx wrote:
I have a few people who asked me this as well, RAID10 or similiar
(SW). I am not so sure, with RAID1 you can have your root disks
on it and boot from it using LILO/GRUB and it is proven pretty
stable; can the same be said about RAID10?
For your boot partition, use raid1 - not raid10.
For others, you get to choose.
The md/raid10 module was created to make is easier to manage a
combination of striping and mirroring, and to provide extra
functionality such as handling an odd number of drives, and 'far' or
'offset' modes which provide raid0-like read performance.
And this is the first (of two) reasons to use RAID-10, it's fast. Even
with a boatload of read ahead, RAID-1 will give you peak read speed of
about that of a single drive. RAID-10 will run at multiples of that.
Okay, you mean the difference between RAID-1 and RAID-10. But the
difference between RAID-(1+0) combination and RAID-10 (in "near"
mode) should be marginal ?!
So, when looking at the raid r/w performance, is the following table
correct ?
+-------------+------------+-------------+
| raid type | read perf. | write perf. |
+-------------+------------+-------------+
+ none/1 HDD | = + = +
+-------------+------------+-------------+
+ raid 1 | = + = +
+-------------+------------+-------------+
+ raid 1+0 | + + + +
+-------------+------------+-------------+
+ raid10(near)| + + + +
+-------------+------------+-------------+
+ raid10(far) | ++ + - +
+-------------+------------+-------------+
Best regards
Thimo Eichstaedt
Raid1 is + if you can do (i believe it is 3) simultaenous reads at the
same time, when I do this I see > 120MB/s from my raid1 raptors.
The "3" can be an issue, I can only be sure that when I'm reading the
number of readers is >0. And with "just one" RAID-10 is faster (asuming
far or offset config).
--
bill davidsen <davidsen@xxxxxxx>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979
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