Re: [squid-users] Hypothetically comparing SATA\SAS to NAS\SAN for squid.

Thanks Marcus,

I indeed understood the subject in more depth.
For now I do look for couple answers about the IOPS tools I can use.
I will just say that on the next squid RPM release I will write about
somethings related to these subjects.
On what level would be the way to test\verify the IOPS?
To me it seems like it's not the FS but the more lower levels of the
devices.
I am asking my self about when testing IOPS what would be the way to
measure it?
Since we have the maximum per the device and the current usage it is
fairly weird to even test.
The basic assumption when testing should be first ACCEPT and only then
REJECT from my understanding.
I heard couple things about the kernel this and the kernel that and
these are like this and that but it requires more then just the basics
to say that.
It is very confusing what tool to measure with the disk quality or the
disk performance.
The kernel might be blame of couple things but I would not expect a 5400
RPM drive to be faster then the speed of light which from what I have
understood is something users "want".
is there anyone that can actually read this thing:
$ iostat /dev/sda -d 2
Linux 3.11.0-15-generic (eliezer-HP) 22/01/14 _x86_64_ (4 CPU)

Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 5.85 95.47 136.58 128853206 184347015

Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 0.00 0.00 0.00 0 0

Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 1.00 0.00 20.00 0 40

Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 0.00 0.00 0.00 0 0

I am trying to understand how kB or kb or tps is converted into IOPS?
bits I know bytes I know Kilo I know and disk that cuts metal I know.
one bytes = 8 bits
one Kbyte = 8 bits * 1024
one IO = ??

Thanks In Advance,
Eliezer

On 20/01/14 03:21, Marcus Kool wrote:
>
> The raw transfer speed of a disk is only interesting when an application
> does
> very large sequential I/Os and squid does not do that.
> Squid writes a lot to disk and reads relatively little and since the
> average object size is
> often around 13 KB, this is also the average I/O size.
> A better performance parameter of disks is I/Os per second (IOPS).
> Average latency is also an interesting parameter but usually the IOPS is
> the
> more important parameter.
>
> The following numbers indicate the speed of disk systems for random 16K
> I/O:
> individual disk: 75-200 IOPS
> individual SSD: 1000-60000 IOPS
> internal RAID disk array with 12 disks and battery backed cache:
> 600-2000 IOPS
> high end SAN or NAS with RAID: 600-20000+ IOPS
Received on Wed Jan 22 2014 - 12:13:40 MST