[ltp] Slightly OT: Filesystem performance on SSD vs HDD: test data request

[Volker Krueger]

Hi,again,

I re-ran the program again with the processor speed fixed to 1.87GHz.
The performance is slightly different now:
0.000u 0.024s 0:00.37 5.4%	0+0k 0+8192io 0pf+0w
0.004u 0.024s 0:00.39 5.1%	0+0k 0+8192io 0pf+0w
0.000u 0.028s 0:00.68 2.9%	0+0k 0+8192io 0pf+0w

With the processor fixed to 800MHz, I get
0.000u 0.036s 0:00.55 5.4%	0+0k 0+8200io 0pf+0w
0.000u 0.052s 0:00.77 6.4%	0+0k 0+8192io 0pf+0w
0.004u 0.040s 0:00.57 7.0%	0+0k 0+8192io 0pf+0w

best,
Volker

Richard Neill wrote:
> Dear All,
>
> I've been looking into filesystem performance for postgresql on
> various configurations. I've found out quite a lot. I'm still curious
> about how it works on a really good SSD; does anyone have an Intel
> X-25 that they would be willing to run a simple test with?
>
> * Postgresql's main issue is when it is doing writes, and is
> frequently very very much i/o-bound. The important measurement is
> fdatasync() speed, not write throughput.
>
> * I have 2 nearly equivalent test machines (apart from the disks):
>
>      T60p, Core 2.0 GHz, 100GB, 7200 rpm HDD (travelstar)
>      Ubuntu Hardy
>
>      X60,  Core 2.0 GHz, 64 GB SSD (OCZ Core 2)
>      Ubuntu Jaunty
>
> In normal use, the X60 feels faster, and I am very happy with the SSD
> for day-to-day use. But postgres really feels slow.
>
>
> * What I've measured so far:
>
>     Test                         Time on X60    Time on T60p
>
>   hdparm -t            94 MB/s        48 MB/s
>
>   syncspeed (ext2)              3.71 s           0.78 s
>   syncspeed (ext3)              11.4 s           2.1 s
>   syncspeed (ext4)              5.9 s            n/a
>
>
> The T60p is running a kernel which doesn't support ext4
> syncspeed is a simple c program - see below
>
>
>
> * Implications (approximately)
>
>   => The SSD is much faster for reads.
>
>   => The SSD is 5 times slower for writes.
>
>   =>  Ext2 is 3 times faster than Ext3 for database workloads
>       [But it may not be as reliable]
>
>   =>  Ext4 is 2 times faster than Ext3
>
>
> * However, I know that the X-25 is supposed to be very much better than
>   almost all the competing SSDs.   Would any X-25 owner be prepared to
>   run the following test:
>
>
>    compile syncspeed (attached):
>        make syncspeed
>    run test:
>        rm -f test.dat; time ./syncspeed test.dat
>
>    The result will be something like:
>       real    0m2.044s
>       user    0m0.000s
>       sys     0m0.048s
>
>    Let me know what the filesystem is too.
>
>
>
> Thanks very much for your input,
>
> Richard
>
>