FreeNAS with raid-5

The previous setup was working fine. But today I acquired a third 250GB drive. So I'm going to give a raid5 setup a try. Why? Because I'm curious and I'm wondering whether there is a cpu-penalty when running a software raid5 in freenas.

So I took out the 1TB samsung drive and built these three harddisk in:

hd0: maxtor diamondmax 10 6V260F0 sataII NCQ (jumper on sataI)
hd1: maxtor diamondmax 10 6V260F0 sataII NCQ (jumper on sataI)
hd2: maxtor diamondmax 10 6L250S0 sataI

In freeNAS I configured a raid5 with 3 drives formatted in softraid. I takes a while to rebuild the array. But the current status is complete see below.

Software RAID information and status
Geom name: CherRaid5
State: COMPLETE CALM
Status: Total=3, Online=3
Type: AUTOMATIC
Pending: (wqp 0 // 0)
Stripesize: 131072
MemUse: 378880 (msl 9)
Newest: -1
ID: 1726283426
Providers:
1. Name: raid5/CherRaid5
 Mediasize: 501998157824 (468G)
 Sectorsize: 512
 Mode: r1w1e2
Consumers:
1. Name: ad10
 Mediasize: 251000193024 (234G)
 Sectorsize: 512
 Mode: r2w2e3
 DiskNo: 0
 Error: No
2. Name: ad8
 Mediasize: 251000193024 (234G)
 Sectorsize: 512
 Mode: r2w2e3
 DiskNo: 2
 Error: No
3. Name: ad6
 Mediasize: 250999111168 (234G)
 Sectorsize: 512
 Mode: r2w2e3
 DiskNo: 1
 Error: No

So three drives with 234GB results in 468GB of free space. When writing files on the NAS the cpu load is the same as before around 20%.

But a new issue had come up --> temperatures are rising. The disk temperatures are rising above 40 degrees celsius. So I put an extra 12cm fan in the case but temperatures are still too high about 35 degrees celsius. Also the power consumption has risen to about 95 Watt.

Data safety is nice, but I'm probably going to put the samsung drive back.