Re: Software RAID5 with 2.6.0-test

[Pavel Machek <pavel@ucw.cz>]

Hi!

> Now that I'm posting anyway - I thought of a plus for the HW RAID
> controllers (hey, they're way behind on the scoreboard so far, so I
> might as well be a gentleman and give them a point or two):
> *) Battery backed write cache
> 
> This will allow the controller to say 'ok I'm done with your sync()',
> way before the data actually reaches the disk platters.  For some

Well, this would mean not only battery-backed controller,
but battery-backed drives, too. (Unless you want to assume that
memory-backup-battery never goes empty).

> While on that topic: SDRAM PCI cards with battery backup can be had
> relatively cheap up to at least a few gigabytes.  It'd be pretty cool to
> have the kernel recognize that for buffer storage. I could see the fun
> in doing half a million random writes and a sync(), and having the
> system tell me it's done the microsecond I issue the sync().

Sync would still take some time as it still makes sense to
do writeback... Main memory is still faster than PCI.
				Pavel 
-- 
				Pavel
Written on sharp zaurus, because my Velo1 broke. If you have Velo you don't need...