6. Performance

You will find here the synthesis of our tests, those are the figures which we recorded on our gigabits network , the performances can vary for your specific use but they will give you a good idea of the effectiveness of the architecture of the storage system.

6.1 Raw performance

You will find here the average scores we were able to get during our read/write tests of big files ( more than 100 GB). We obtained the maximum performance of the server.

 

Max usable capacity

Write, MB/sec

Read, MB/sec

Double parity RAID

1.41 TB

165

190

Double parity RAID, wide stripes

1.42 TB

155

170

Mirrored

803 GB

196

248

Single parity RAID, narrow stripes

1.17 TB

171

244

Striped

1.83 TB

202

246


CPU load is 70% while writing data ( and up to 80% using double parity) and is 60% while reading.

6.2 Performance on heavy load

Our tests showed that performance is little impacted by the number of simultaneous users, the overload will neither come from a too big number of users nor from the number of file manipulated.

The biggest source of overload is the number of access regarding small files (read or write). In our test we created thousands of small files ( 1 KB ).
To compare, a standard disk ( 7200rpms) used under Windows XP is able to write 8192 files of 1KD in 9.2 seconds(0.86 MB/s), the reading of these 8192 files takes 8.4 seconds (0.95 Mo/s) …

 

Max usable capacity

Write, MB/sec

Read, MB/sec

Double parity RAID

1.41 To

2.2

1.9

Double parity RAID, wide stripes

1.42 To

1.2

1.9

Mirrored

803 Go

2.6

1.9

Single parity RAID, narrow stripes

1.17 To

1.8

1.9

Striped

1.83 To

3.2

2.0

CPU load is 50% while writing and 10% while reading.

6.3 Performance in degraded mode

During the rebuilding (scrub) of the filesystem following the replacement of a deffective harddisk, ZFS repairs itself and checks the intergrity of the data, this operation is very ressource intensive and impacts services.
A full rebuilding will take an hour, performance are degraded during this time:
- max row performance : 67 MB/sec while writing, 79 MB/sec while reading
- performance under heavy load : 1.7 MB/sec while writing , 1.5 MB/sec while reading

The system is still performing well and responsivness is always good during this critical moment.

Error 16

If the startup stalls and you see this message:

Booting 'Sun Storage 7110 2008.10.23,1-0'

findroot (system,0,a)
Filesystem type is zfs, partition type 0xbf
bootfs system/boot/ak-nas-2008.10.23_1-0
kernel$ /platform/i86pc/kernel/$ISADIR/unix -B zfs-bootfs=system/67,console=ttya,ttya-mode="9600,8,n,1,-"
loading '/platform/i86pc/kernel/$ISADIR/unix -B zfs-bootfs=system/67,console=ttya,ttya-mode="9600,8,n,1,-"' ...
cpu: 'AuthenticAMD' family 16 model 2 step 3
[BIOS accepted mixed-mode target setting!]
[Multiboot-kludge, loadaddr=0xbffe38, text-and-data=0x17b8c8
Error 16: Inconsistent filesystem structure

Don't panic, the hardware initialization failed, all you need is to do is to restart the server to fix the issue.