8.0-RELEASE/amd64 - full ZFS install - low read and write disk performance

[James R. Van Artsdalen]

Dan Naumov wrote:
> [jago at atombsd ~]$ dd if=/dev/zero of=/home/jago/test2 bs=1M count=4096
> 4096+0 records in
> 4096+0 records out
> 4294967296 bytes transferred in 143.878615 secs (29851325 bytes/sec)
>
> This works out to 1GB in 36,2 seconds / 28,2mb/s in the first test and
> 4GB in 143.8 seconds / 28,4mb/s
For the record, better results can be seen.  In my test I put 3 Seagate
Barracuda XT drives in a port multiplier and connected that to one port
of a PCIe 3124 card.

The MIRROR case is at about the I/O bandwidth limit of those drives.

[root at kraken ~]# zpool create tmpx ada{2,3,4}  
[root at kraken ~]# dd if=/dev/zero of=/tmpx/test2 bs=1M count=4096
4096+0 records in
4096+0 records out
4294967296 bytes transferred in 20.892818 secs (205571470 bytes/sec)
[root at kraken ~]# zpool destroy tmpx
[root at kraken ~]# zpool create tmpx mirror ada{2,3}
[root at kraken ~]# dd if=/dev/zero of=/tmpx/test2 bs=1M count=4096
4096+0 records in
4096+0 records out
4294967296 bytes transferred in 36.432818 secs (117887321 bytes/sec)
[root at kraken ~]#