Hardware for EROS? SSD+HD

[Jonathan S. Shapiro]

Valerio is certainly right, but I actually had something else in mind
entirely. EROS and KeyKOS are appropriately transacted already by virtue of
the way the checkpoint system works. A battery-backed log used as a
replicate of an on-disk log would be a fine solution. You write the
checkpoint area to BOTH battery-backed and stable storage, and use the
battery backed area for rapid recovery when/if it is still valid. Depending
on access times, it would also usefully serve as a large, relatively stable
cache between the main memory and the disk.

That is, there is no need for a backup disk to be built in to the solid
state device if the operating system already has systemwide stabilization
transactions.

> it is sure that only with a battery backup an SSD will cause problems with
extended
> power outages....