Re: "big" machines running Debian?
2009-02-26_14:21:54-0500 "Douglas A. Tutty" <dtutty@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.
--
Ron Peterson
Network & Systems Manager
Mount Holyoke College
http://www.mtholyoke.edu/~rpeterso
-
I wish my computer would do what I want it to do - not what I tell it to do.
Reply to: