On Sat, 20 Jun 2026, J. Hannken-Illjes wrote:
Others will know better, but I always thought a Raid5 with four disks spends most time with read-modify-write cycles as usually no requests will fit the stripe size.
Yes, with RAIDframe RAID-5 you want (2^n)+1 disks because of parity being separate, so your MAXPHYS data needs to split neatly across the remaining data disks. You are trying to split your data across 3 disks...
Also make sure you align everything for 4K sectors. But, yes, I vote for using ZFS too.
On 20. Jun 2026, at 18:55, smurfd <[email protected]> wrote: Hey, This will be a long one, sorry for this. I have created a RAID5 NAS using NetBSD 10.1, and im experiencing slow writing speeds. Or is my expectations all wrong? :) I earlier had FreeBSD and ZFS zraid on the same Ugreen DXP4800 plus (https://nas-eu.ugreen.com/products/ugreen-nasync-dxp4800-plus-nas-storage) The NAS drives are 4x7TB, less than a year old Segate Ironwolf NAS 3.5". NetBSD is installed first on the SSD, using a base install. Then the Raid is created manually... Have asked here: https://www.unitedbsd.com/d/1646-raid5-slow-write-on-big-disks/8 Just now redid the raid, for the Xth time, to compare the speeds i got using FreeBSD (because i didnt remember/had that written down) I know, comparing zraid vs raid5 is like comparing apples to oranges, right?... What write speeds should i expect?! is probably the most important question... Or where did i go wrong, because user error is VERY likely. First, i tried to follow the Summary section in the https://man.netbsd.org/raidctl.8, realizing that Disklabel supports no larger than 2TB disks. So found this: https://wiki.netbsd.org/users/mlelstv/using-large-disks/ and tried to follow the Raidframe section. Then i got the correct size i expected... The speed though, is slow! (again compared to zfs zraid) When i had FreeBSD installed, i did the following. Installed the system to the SSD. Then, did this, where **** is repeaded 4 times for the disks... # gpart destroy -F ada0 **** # gpart create -s gpt ada0 **** # gpart add -t freebsd-zfs ada0 **** # zpool create -f island raidz /dev/ada0p1 /dev/ada1p1 /dev/ada2p1 /dev/ada3p1 (this was instant) island/scumm 21T 140K 21T 0% /zstorage/scumm This is the speed... # dd if=/dev/zero bs=1024k count=1000 of=/zstorage/scumm/test.txt 1048576000 bytes transferred in 0.259733 secs (4037123661 bytes/sec) # dd if=/dev/zero bs=4096k count=1000 of=/zstorage/scumm/test.txt 4194304000 bytes transferred in 1.534966 secs (2732505282 bytes/sec) # dd if=/dev/zero bs=1024 count=1000 of=/zstorage/scumm/test.txt 1024000 bytes transferred in 0.004667 secs (219403356 bytes/sec) Then on NetBSD, installed on the SSD i did this: # gpt destroy wd0 **** # gpt create -Af wd0 **** # gpt add -t raid -l raid5@wd0 -b $(( 2048 )) -s 15628051053 wd0 **** # raidctl -C /etc/raid5.conf raid5 # raidctl -I 13371337 raid5 # raidctl -iv raid5 (This took around 72+ hours) # gpt create -Af raid5 # gpt add -a 1024 -t ffs -l island raid5 /dev/rraid5: Partition 1 added: 49f48d5a-b10e-11dc-b99b-0019d1879648 34 46884152860 # dkctl raid5 addwedge island 34 46884152860 ffs # newfs -O2 -b 65536 -s -1g /dev/dk7 (trying to enable https://man.netbsd.org/wapbl.4) # tunefs -l 1g /dev/dk7 # mount -o log /dev/dk7 /mnt # umount /mnt # mount /dev/dk7 /mnt/island/ /dev/dk7 22T 8.0K 21T 0% /mnt/island from /etc/fstab /dev/dk7 /mnt/island ffs rw,noatime,log 1 1 This one, was done before initializing the raid, on one disk nas1# dd if=/dev/zero bs=1024k count=1000 of=/mnt/test.txt 1048576000 bytes transferred in 2.201 secs (476408905 bytes/sec) Writing to the raid: nas1# dd if=/dev/zero bs=1024k count=1000 of=/mnt/island/test.txt 1048576000 bytes transferred in 68.984 secs (15200278 bytes/sec) nas1# dd if=/dev/zero bs=4096k count=1000 of=/mnt/island/test.txt 4194304000 bytes transferred in 478.951 secs (8757271 bytes/sec) nas1# dd if=/dev/zero bs=1024 count=1000 of=/mnt/island/test.txt 1024000 bytes transferred in 0.054 secs (18962962 bytes/sec) If i tried bs=512k and count=1000, i get around 1.6Billion bytes per sek write, woohoo... Then try the same with count=2000 and get 1.3 million bytes per sek write hmmm .... This is /etc/raid5.conf START array # numRow numCol numSpare 1 4 0 START disks /dev/dk3 /dev/dk4 /dev/dk5 /dev/dk6 START layout # sectPerSU SUsPerParityUnit SUsPerReconUnit RAID_level_5 32 1 1 5 START queue fifo 100 Summary: It seems like this is 200 times slower than FreeBSD zraid, is that reasonable? or where did i go wrong?! Again, only curious. Was thinking about installing OpenBSD, they have a more similar raid system compared to netbsd(more or less exactly the same:)) Could it be worth adding a Big disk section to the raidctl manpage: https://man.netbsd.org/raidctl.8 Thanks in advance! Br Nicklas
