On 02/26/2009 01:49 PM, Ron Peterson wrote:
2009-02-26_14:21:54-0500 "Douglas A. Tutty" <dtu...@vianet.ca>:
On Wed, Feb 25, 2009 at 08:53:45PM -0600, Ron Johnson wrote:
On 02/25/2009 07:22 PM, Douglas A. Tutty wrote:
[snip]
/proc/megaraid/hba0/raiddrives-0-9
Logical drive: 0:, state: optimal
Span depth: 1, RAID level: 1, Stripe size: 64, Row size: 2
Read Policy: Adaptive, Write Policy: Write thru, Cache Policy: Cached IO
Logical drive: 1:, state: optimal
Span depth: 0, RAID level: 0, Stripe size:128, Row size: 0
Read Policy: No read ahead, Write Policy: Write thru, Cache Policy: Cached
IO
Why is Read Ahead disabled on Logical Drive 1?
My understanding is that "read ahead" in this case refers to the ability
of the raid card to read ahead from one disk while a read is taking
place on another disk. This only makes sense in a redundant raid level.
LD1 is raid0, so there is no other disk from which to read ahead.
My understanding is that read ahead means the controller reads more data
into memory than you asked for, expecting that the next bits you ask for
will be immediately after the ones you just got.
That *is* the standard definition. Though there's nothing stopping
Megaraid from being weird.
--
Ron Johnson, Jr.
Jefferson LA USA
The feeling of disgust at seeing a human female in a Relationship
with a chimp male is Homininphobia, and you should be ashamed of
yourself.
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