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Cc: freebsd-hackers@freebsd.org
Subject: Re: Request for opinions - gvinum or ccd?
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>> (very roughly, in the non-sequential access case) expected to deliver
>> performance of four drives in a RAID0 array?
>
> According to all the Sun documentation, the I/O throughput of a raidz
> configuration is equal to that of a single drive.

exactly what i say. it's like RAID3. Not RAID5 which have close to n times 
single drive throughput on read and rougly n/4 on writes.

> We remade the pool using 3x 8-drive raidz2 vdevs, and performance has
> been great (400 MBytes/s write, almost 3 GBytes/s sequential read, 800

why write performance is so slow? in Sun theory it should have the same 
speed as reads. I would say that it should be even better a bit - 
filesystem get data first in cache and can plan ahead.

> MBytes/s random read).

random read on how big chunks?

Are you sure you get 3GB/s on read? it would mean each drive must be able 
to do 140MB/s

What disks do you use?