lkml.org 
[lkml]   [2008]   [Mar]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [ANNOUNCE] Ramback: faster than a speeding bullet
On Sat, Mar 15, 2008 at 4:26 PM, Pavel Machek <pavel@ucw.cz> wrote:
> On Thu 2008-03-13 12:03:03, Daniel Phillips wrote:
> > On Thursday 13 March 2008 12:50, David Newall wrote:
> > > Daniel Phillips wrote:
> > > > The period where you cannot access the data is downtime. If your script
> > > > just does a cp from a disk array to the ram device you cannot just read
> > > > from the backing store in that period because you will need to fail over
> > > > to the ramdisk at some point, and you cannot just read from the ramdisk
> > > > because it is not populated yet.
> > >
> > > Wouldn't a raid-1 set comprising disk + ramdisk do that with no downtime?
> >
> > In raid1, write completion has to wait for write completion on all
> > mirror members, so writes run at disk speed. Reads run at ramdisk
> > speed, so your proposal sounds useful, but ramback aims for high
> > write performance as well.
>
> raid1 + kflushd tweak?
>
> special raid1 mode that signals completion when it hits _one_ of the
> drives, and does sync when the slower drive is idle?

raid1 already supports marking member(s) as write-mostly. Any
write-mostly member can also make use of write-behind mode (provided
you have a write intent bitmap).


\
 
 \ /
  Last update: 2008-03-15 21:43    [W:0.103 / U:0.100 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site