The MegaRAID 320-2E is the latest and perhaps
greatest U320 SCSI RAID card from LSI. Unlike
the previous two cards in this article, the 320-2E
has a PCI Express x8 interface, allowing it to be
more usable with even the least expensive
motherboards. The 320-2E has an older brother,
the 320-2X, which uses the PCI-X 133MHz interface.
Comparing its specs with the 320-2E, we've concluded
that the 320-2E is slightly more advanced in a few
ways, one of which is its faster DDR cache memory.
Here we go with the results.
We decided to try increasing the cache of the
320-2E to its maximum and see if it had any
noticeable effect on our 2-drive setup.
theoretically, it should not, as cache memory
typically helps in large arrays with many small
reads and writes, especially in RAID-5 and 6
configurations. Check out the two screen
shots showing "512MB cache":
HD Tach 3.0.1.0, 8MB
Zones, RAID-0, 8k stripe
HD Tach 3.0.1.0, 32MB
Zones, RAID-0, 8k stripe
NOT TESTED
ATTO Mark, RAID-0, 8k
stripe
HD Tach 3.0.1.0, 8MB
Zones, RAID-0, 128k stripe
HD Tach 3.0.1.0, 32MB
Zones, RAID-0, 128k stripe
HD Tach 3.0.1.0, 32MB
Zones, RAID-0, 128k stripe, 512MB cache
Looks like the increased cache did not help much
aside from the bigger burst speed...
NOT TESTED
ATTO Mark, RAID-0,
128k stripe
HD Tach 3.0.1.0, 8MB
Zones, RAID-1
HD Tach 3.0.1.0, 32MB
Zones, RAID-1
NOT TESTED
ATTO Mark, RAID-1
ATTO Mark, Software
RAID-0
ATTO Mark, Software
RAID-0, 512MB cache
Similar story here with the increased cache.
It seems to indicate that the cost of adding it
is not worth the expense in this particular
configuration. But for larger arrays and
server patterns, I'm sure the story will be
different. But we're running workstations
here, not servers.
