I have problems with understanding these zfs read results, im using napp-it. To make the benchmarks go faster i use a solaris VM with only 2 GB ram, but i get the same results with 8 GB ram. The disks are old 500 GB samsung 7200 RPM drives. The drives are passed-through from a M1015 to the solaris VM.
Using a clean solaris 11 install, mirror setup, zpool iostat gives me the following during the dd write/read benchmark running from napp-it.
The result:
Using a single disk and benchmarking it i get these results.
Questions
Why am i not seeing twice the read performance using a mirror setup? I have read that using a mirror i should get double the read performance since ZFS uses a round-robin technique to obtain the data. Using zpool iostat i see that one device is performing ~44 MB/s while the other is showing ~100 MB/s. Creating single pools of the devices and running tests i see identical performance.
I plan on buying SSDs to replace these old drives (they are currently for esxi datastore), but i feel i need to solve this issue first so i wont run into it later.
EDIT
If i use another solaris vm with the latest updates i am seeing different performance,
In this case i get half the read performance from each disk, to a total of 50 MB/s according to zpool iostat. However i still get better dd results than using the other solaris machine for some reason.
Using a clean solaris 11 install, mirror setup, zpool iostat gives me the following during the dd write/read benchmark running from napp-it.
Code:
capacity operations bandwidth
pool alloc free read write read write
----------- ----- ----- ----- ----- ----- -----
tank 3.91G 460G 1.40K 0 178M 0
mirror 3.91G 460G 1.40K 0 178M 0
c5t13d1 - - 803 0 134M 0
c5t14d1 - - 166 0 44.0M 0
----------- ----- ----- ----- ----- ----- -----
Code:
Memory size: 2048 Megabytes
write 4.194304 GB via dd, please wait...
time dd if=/dev/zero of=/tank/dd.tst bs=2048000 count=2048
2048+0 records in
2048+0 records out
real 1:18.5
user 0.0
sys 2.1
4.194304 GB in 78.5s = 53.43 MB/s Write
wait 40 s
read 4.194304 GB via dd, please wait...
time dd if=/tank/dd.tst of=/dev/null bs=2048000
2048+0 records in
2048+0 records out
real 1:26.4
user 0.0
sys 2.3
4.194304 GB in 86.4s = 48.55 MB/s Read
Code:
---------- ----- ----- ----- ----- ----- -----
tank 3.91G 460G 620 0 154M 0
c5t13d1 3.91G 460G 620 0 154M 0
---------- ----- ----- ----- ----- ----- -----
Code:
write 4.194304 GB via dd, please wait...
time dd if=/dev/zero of=/tank/dd.tst bs=2048000 count=2048
2048+0 records in
2048+0 records out
real 55.1
user 0.0
sys 2.3
4.194304 GB in 55.1s = 76.12 MB/s Write
wait 20 s
read 4.194304 GB via dd, please wait...
time dd if=/tank/dd.tst of=/dev/null bs=2048000
2048+0 records in
2048+0 records out
real 1:36.2
user 0.0
sys 1.8
4.194304 GB in 96.2s = 43.60 MB/s ReadWhy am i not seeing twice the read performance using a mirror setup? I have read that using a mirror i should get double the read performance since ZFS uses a round-robin technique to obtain the data. Using zpool iostat i see that one device is performing ~44 MB/s while the other is showing ~100 MB/s. Creating single pools of the devices and running tests i see identical performance.
I plan on buying SSDs to replace these old drives (they are currently for esxi datastore), but i feel i need to solve this issue first so i wont run into it later.
EDIT
If i use another solaris vm with the latest updates i am seeing different performance,
Code:
capacity operations bandwidth
pool alloc free read write read write
----------- ----- ----- ----- ----- ----- -----
tank 15.3G 449G 410 0 51.1M 0
mirror 15.3G 449G 410 0 51.1M 0
c5t13d1 - - 32 0 24.5M 0
c5t14d1 - - 33 0 26.6M 0
Last edited: