Stacy White wrote:

We're in the process of buying another Opteron server to run Postgres, and
based on the suggestions in this list I've asked our IT director to get an
LSI MegaRaid controller rather than one of the Adaptecs.

But when we tried to place our order, our vendor (Penguin Computing) advised
"we find LSI does not work well with 4GB of RAM. Our engineering find that
LSI card could cause system crashes. One of our customer ... has found that
Adaptec cards works well on PostGres SQL

Probably, your vendor is trying to avoid problems at all, but
"one of our customers" is not a pretty general case, and
"we find LSI does not work well", but is there a documented reason?

Anyway, my personal experience has been with an Acer Altos R701 + S300
external storage unit, equipped with LSI Logic Megaraid U320 aka
AMI Megaraid aka LSI Elite 1600
(honestly, these cards come with zillions of names and subnames, that
I don't know exactly how to call them).

This system was configured in various ways. The final layout is
3 x RAID1 arrays (each of 2 disks) and 1 x RAID10 array (12 disks).
This configuration is only available when you use 2 LSI cards (one
for each S300 scsi bus).

The system behaves pretty well, with a sustained sequential write rate
of 80Mb/s, and more importantly, a quite high load in our environment
of 10 oltp transactions per second, without any problems and
`cat /proc/loadavg` < 1.

I don't like the raid configuration system of LSI, that is
counter-intuitive for raid 10 arrays. It got me 4 hours and
a tech support call to figure out how to do it right.

Also, I think LSI cards don't behave well with particular
raid configurations, like RAID 0 with 4 disks, or RAID 10
with also 4 disks. It seemed that these configurations put
the controller under heavy load, thus behaving unreasonably
worse than, for example, 6-disks-RAID0 or 6-disks-RAID1.
Sorry, I can't be more "scientific" on this.

For Adaptec, I don't have any direct experience.


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