Strange Performance problem - help

S

sahostking

Renowned Member
Oct 6, 2015
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Cape Town, South Africa
www.hostking.host
Hi

Got 2 servers same spec besides one has a HW raid controller in RAID 10 with BBU writeback on ext3 which gives the following with no VMs on it yet:

root@vz-cpt-1:~# dd if=/dev/zero of=test bs=1024k count=16k conv=fdatasync; unlink test
16384+0 records in
16384+0 records out
17179869184 bytes (17 GB) copied, 56.9353 s, 302 MB/s

root@vz-cpt-1:~# dd if=/dev/zero of=test bs=64k count=16k conv=fdatasync; unlink test
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB) copied, 3.36386 s, 319 MB/s

root@vz-cpt-1:~# pveperf
CPU BOGOMIPS: 57601.56
REGEX/SECOND: 1902166
HD SIZE: 196.86 GB (/dev/mapper/pve-root)
BUFFERED READS: 408.02 MB/sec
AVERAGE SEEK TIME: 6.98 ms
FSYNCS/SECOND: 4999.66
DNS EXT: 132.71 ms
DNS INT: 19.54 ms

Whereas another proxmox server with 4 KVM VMs on it and ZFS RAID10 gives this:

root@vz-cpt-2:/var/lib/vz# dd if=/dev/zero of=test bs=64k count=16k conv=fdatasync; unlink test
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB) copied, 0.882696 s, 1.2 GB/s

root@vz-cpt-2:/var/lib/vz# dd if=/dev/zero of=test bs=1024k count=16k conv=fdatasync; unlink test
16384+0 records in
16384+0 records out
17179869184 bytes (17 GB) copied, 6.69261 s, 2.6 GB/s

root@vz-cpt-2:/var/lib/vz# pveperf
CPU BOGOMIPS: 55994.88
REGEX/SECOND: 2703129
HD SIZE: 5448.00 GB (rpool/ROOT/pve-1)
FSYNCS/SECOND: 38.94
DNS EXT: 138.54 ms
DNS INT: 20.29 ms


Now ZFS server seems far faster ? Just bad fsync I see though.
Does this indicate throw away HW Raid Controller and stick to ZFS rather?
 
Last edited:
hi

zfs uses compression. turn off compression or use uncompressable data for benchmarking. 300 MB/s should be fine for raid 10. fsync for zfs is ok for regular disks
 
Ok I see what you mean with compression it gives 1GB/s + whereas without compression gives me:

root@vz-cpt-2:~# dd if=/dev/zero of=test bs=1024k count=16k conv=fdatasync; unlink test
16384+0 records in
16384+0 records out
17179869184 bytes (17 GB) copied, 78.0471 s, 220 MB/s
root@vz-cpt-2:~# dd if=/dev/zero of=test bs=64k count=16k conv=fdatasync; unlink test
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB) copied, 4.24248 s, 253 MB/s


Looks more realistic now
 
I decided to take out HW Raid card and put setup a Software raid with ext 4 and lvm and strangely get results closer to HW raid speed:

[root@vz-cpt-2 ~]# dd if=/dev/zero of=test bs=64k count=16k conv=fdatasync; unlink test
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB) copied, 3.58775 s, 299 MB/s
[root@vz-cpt-2 ~]# dd if=/dev/zero of=test bs=1024k count=16k conv=fdatasync; unlink test
16384+0 records in
16384+0 records out
17179869184 bytes (17 GB) copied, 56.4155 s, 305 MB/s


Maybe software raid is just as good as HW raid now adays :)
 
ZFS offers a lot of features. Most notably checksumming. Depending on your hardware a write error occurs roughly every 12TB.

You should also have a look at read performance. A mirrored ZFS reads from multiple disks simultaneously and ensures data integrity. Read IO is also doubled.

I'm using LSI SAS 9207-8i HBA controller with Samsung SM863 SSDs in multiple mirrored pools with LXC. Works very well so far
Code: 
dd if=/dev/zero of=test bs=64k count=16k conv=fdatasync; unlink test
16384+0 records in
16384+0 records out
1073741824 bytes (1.1 GB) copied, 3.35287 s, 320 MB/s
 
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