On Sat, Apr 25, 2009 at 6:02 PM, Wojciech Puchar
<woj...@wojtek.tensor.gdynia.pl> wrote:
>> thinking that a software raid5 solution may not be such a bad idea.
> software raid5 isn't any more bad than hardware raid5 most cases.
> just raid5 is bad if you use it in ANY type of load except:
> a) mostly reads - then set LARGE RAID stripe size
> b) mostly huge files - then set small RAID stripe size to have highest
> single thread transfer, or large to have higher concurency.
> EVERY OTHER case is bad case for RAID5 - just remember small write on
> RAID5=2 reads+2 writes on disks.

True, but aren't both steps done in parallel? So a single-disk
equivalent is actually just one read for every write.

>> The question is what port multiplier hardware does FreeBSD 7 support?
> it unfortunately doesn't. but your hardware RAID controllers drive disks by
> itself and presents virtual drives to system, and system has nothing to do
> with it.
> so ask manufacturer if it supports port multipliers.

The reason I don't want to depend on a hardware implementation is
because this "server" is actually a shuttle xpc box, so not exactly
built for reliability. If something breaks, I have to be able to move
the disks to any other FreeBSD 7 machine and continue accessing the
data. So I really just need some PCIe card and an external enclosure
that will expose all attached disks to the operating system. From
there I will determine how to arrange them, but I'd rather not have
any controller that abstracts away the physical hard drives.

- Max
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