[linux-lvm] Re: [PATCH] 64 bit scsi read/write

[Steven Lembark]

- Alan Cox <alan at lxorguk.ukuu.org.uk> on 07/14/01 09:45:44 +0100:

>> If, after a power outage, the IDE disk can keep going for long enough
>> to write its write cache out to the reserved vendor area (which will
>> only take 20-30 milliseconds) then the data may be considered *safe*
>> as soon as it hits writecache.
> 
> Hohohoho.

Don't laugh, it works.  A 10KRPM drive has enough inertia and
stored charge to write a full cyl in less time than the BFC's in 
the switcher can discharge.

>> If I'm right then the only open question is: which disks do and
>> do not do the right thing when the lights go out.
> 
> As far as I can tell none of them at least in the IDE world

Some SCSI's will use intertia to write a single cyl if the power
goes out.  I've never seen a spec for IDE's that allows for this.

One more reason to use SCSI.