We (a small college with about 3000 active accounts) are currently in
the process of moving from UW IMAP running on linux to dovecot running
on a cluster of 3 or 4 new faster Linux machines. (Initially using
perdition to split the load.)
As we are building and designing the system, I'm attempting to take (or
find) benchmarks everywhere I can in order to make informed decisions
and so that when we need something faster we have something to compare
it to. I've looked all over the Internet and I haven't seen very many
good benchmarks running on recent hardware for things like this. Even
simple things like how different raid levels perform with fast CPUs and
really fast disks.
We recently got the first of the cluster machines (which has the
following specs: (from penguin computing)
2x 1.6ghz woodcrest (so 4 cores total)
2g ram (we may upgrade to more, depending on what we seem to need)
6x 15k SAS 73G hard drives.
I've always read that RAID 10 is the RAID of choice for mail, because
the checksums take time and whatnot, but on a system that fast I'm sure
that's not an issue (which I could see from the cpu usage during
benchmarks.) We were also wondering whether RAID6 would be a good option
since it would give more redundancy. (raid6 allows 2 drive failures)
All tests were run on ext3 with all 6 disks in the raid. Everything is
using Linux software raid.
I used bonnie++ to run the benchmarks, and here are the initial results
we got:
Output Input
RAID "Per Chr" "Block" "Per Chr"
"Block"
RAID6 34628, 97983, 23316, 39077
RAID5 39559, 32715, 32036, 52231
RAID10 38816, 229062, 40645, 267418
I assume that mail running maildir (as we intend to do) is somewhere
between writing one char at a time and writing huge blocks to fill 4g
files. Since the Per Chr values seemed to have maxed out the CPU and
we'll have 4 cores available, I tried the same thing running 4 copies of
bonnie at once and adding the results. (I worked backwards and didn't
bother with raid 6 for obvious reasons)
Output Input
RAID "Per Chr" "Block" "Per Chr"
"Block"
RAID5 37465, 37095, 102828, 174263
RAID10 111239, 128287, 93400, 230320
So, if our system is ever running full out, basically disk bound, it
should be able to handle about 4X as many writes and at least as many
reads using RAID10 than raid 5, and since raid 6 was pretty similar to
raid 5 in the first tests, I assume it will be here too.
I have the full bonnie results if anyone's interested.
I also plan to come up with some basic benchmarks as we start to
actually have dovecot working as we want it to. (Possibly using the macs
in our labs and XGrid as a "client".. finally a use for that thing :)
)
Do people have suggestions as to what to test for a primarily IMAP (+ a
little POP) server? I was thinking of doing something similar to
http://www.courier-mta.org/mbox-vs-maildir/ which selects a mail box,
deletes and expunges a message, fetches a few messages, and then does
some searches.
Also, while I have the opportunity, are there any other benchmarks I
should run? I suppose I could compare dovecot with mbox vs maildir, with
indexing and without. Dovecot with indexing but the indexes deleted,
etc. I could compare dovecot to uw imap.
Anything else? I probably can't justify the time to get cyrus up and
running. (I did that a few months ago when deciding which server to use...)
Ethan Sommer
--
--
Ethan Sommer
Systems Administrator
Gustavus Adolphus College
507-933-7042
sommere at gac.edu
not sure how I messed that up so badly, the first set of numbers were
off. here's the first numbers again:
Output Input
RAID "Per Chr" "Block" "Per Chr"
"Block"
RAID6 38918, 60365, 40098, 301104
RAID5 38689, 64907, 40320, 282653
RAID10 38816, 229062, 40645, 267418
All numbers are KByes/second. So the raid 6 can do block reads at about
300megabytes per second (for one thread) and the 4 threaded raid10
bellow did 230megabytes per second with 4 threads.
Too many numbers in too big a spreadsheet I guess. In any case, that's
what I actually got.
Ethan Sommer wrote:>
> We (a small college with about 3000 active accounts) are currently in
> the process of moving from UW IMAP running on linux to dovecot running
> on a cluster of 3 or 4 new faster Linux machines. (Initially using
> perdition to split the load.)
>
> As we are building and designing the system, I'm attempting to take
> (or find) benchmarks everywhere I can in order to make informed
> decisions and so that when we need something faster we have something
> to compare it to. I've looked all over the Internet and I haven't
seen
> very many good benchmarks running on recent hardware for things like
> this. Even simple things like how different raid levels perform with
> fast CPUs and really fast disks.
>
> We recently got the first of the cluster machines (which has the
> following specs: (from penguin computing)
> 2x 1.6ghz woodcrest (so 4 cores total)
> 2g ram (we may upgrade to more, depending on what we seem to need)
> 6x 15k SAS 73G hard drives.
>
> I've always read that RAID 10 is the RAID of choice for mail, because
> the checksums take time and whatnot, but on a system that fast I'm
> sure that's not an issue (which I could see from the cpu usage during
> benchmarks.) We were also wondering whether RAID6 would be a good
> option since it would give more redundancy. (raid6 allows 2 drive
> failures)
>
> All tests were run on ext3 with all 6 disks in the raid. Everything is
> using Linux software raid.
> I used bonnie++ to run the benchmarks, and here are the initial
> results we got:
> Output Input
> RAID "Per Chr" "Block" "Per Chr"
"Block"
> RAID6 34628, 97983, 23316, 39077
> RAID5 39559, 32715, 32036, 52231
> RAID10 38816, 229062, 40645, 267418
>
> I assume that mail running maildir (as we intend to do) is somewhere
> between writing one char at a time and writing huge blocks to fill 4g
> files. Since the Per Chr values seemed to have maxed out the CPU and
> we'll have 4 cores available, I tried the same thing running 4 copies
> of bonnie at once and adding the results. (I worked backwards and
> didn't bother with raid 6 for obvious reasons)
> Output Input
> RAID "Per Chr" "Block" "Per Chr"
"Block"
> RAID5 37465, 37095, 102828, 174263
> RAID10 111239, 128287, 93400, 230320
>
>
> So, if our system is ever running full out, basically disk bound, it
> should be able to handle about 4X as many writes and at least as many
> reads using RAID10 than raid 5, and since raid 6 was pretty similar to
> raid 5 in the first tests, I assume it will be here too.
>
>
> I have the full bonnie results if anyone's interested.
>
> I also plan to come up with some basic benchmarks as we start to
> actually have dovecot working as we want it to. (Possibly using the
> macs in our labs and XGrid as a "client".. finally a use for that
> thing :) )
>
> Do people have suggestions as to what to test for a primarily IMAP (+
> a little POP) server? I was thinking of doing something similar to
> http://www.courier-mta.org/mbox-vs-maildir/ which selects a mail box,
> deletes and expunges a message, fetches a few messages, and then does
> some searches.
>
> Also, while I have the opportunity, are there any other benchmarks I
> should run? I suppose I could compare dovecot with mbox vs maildir,
> with indexing and without. Dovecot with indexing but the indexes
> deleted, etc. I could compare dovecot to uw imap.
>
> Anything else? I probably can't justify the time to get cyrus up and
> running. (I did that a few months ago when deciding which server to
> use...)
>
> Ethan Sommer
>
--
--
Ethan Sommer
Systems Administrator
Gustavus Adolphus College
507-933-7042
sommere at gac.edu
Hi, we have over 6000 active accounts (half pop3, half imap), and switching from UW+mbox to dovecot+maildir was such an incredible performance boost that the same old hardware was more than enough. Also from our experience, disk I/O was critical with mbox, but not now (we keep using raid5 without performance penalties). Test it before you switch. Aaaaaaaaaaagur. El Martes, 21 de Noviembre de 2006 03:37, Ethan Sommer escribi?:> We (a small college with about 3000 active accounts) are currently in > the process of moving from UW IMAP running on linux to dovecot > running on a cluster of 3 or 4 new faster Linux machines. (Initially > using perdition to split the load.) > > As we are building and designing the system, I'm attempting to take > (or find) benchmarks everywhere I can in order to make informed > decisions and so that when we need something faster we have something > to compare it to. I've looked all over the Internet and I haven't > seen very many good benchmarks running on recent hardware for things > like this. Even simple things like how different raid levels perform > with fast CPUs and really fast disks. > > We recently got the first of the cluster machines (which has the > following specs: (from penguin computing) > 2x 1.6ghz woodcrest (so 4 cores total) > 2g ram (we may upgrade to more, depending on what we seem to need) > 6x 15k SAS 73G hard drives. > > I've always read that RAID 10 is the RAID of choice for mail, because > the checksums take time and whatnot, but on a system that fast I'm > sure that's not an issue (which I could see from the cpu usage during > benchmarks.) We were also wondering whether RAID6 would be a good > option since it would give more redundancy. (raid6 allows 2 drive > failures) > > All tests were run on ext3 with all 6 disks in the raid. Everything > is using Linux software raid. > I used bonnie++ to run the benchmarks, and here are the initial > results we got: > Output Input > RAID "Per Chr" "Block" "Per Chr" "Block" > RAID6 34628, 97983, 23316, 39077 > RAID5 39559, 32715, 32036, 52231 > RAID10 38816, 229062, 40645, 267418 > > I assume that mail running maildir (as we intend to do) is somewhere > between writing one char at a time and writing huge blocks to fill 4g > files. Since the Per Chr values seemed to have maxed out the CPU and > we'll have 4 cores available, I tried the same thing running 4 copies > of bonnie at once and adding the results. (I worked backwards and > didn't bother with raid 6 for obvious reasons) > Output Input > RAID "Per Chr" "Block" "Per Chr" "Block" > RAID5 37465, 37095, 102828, 174263 > RAID10 111239, 128287, 93400, 230320 > > > So, if our system is ever running full out, basically disk bound, it > should be able to handle about 4X as many writes and at least as many > reads using RAID10 than raid 5, and since raid 6 was pretty similar > to raid 5 in the first tests, I assume it will be here too. > > > I have the full bonnie results if anyone's interested. > > I also plan to come up with some basic benchmarks as we start to > actually have dovecot working as we want it to. (Possibly using the > macs in our labs and XGrid as a "client".. finally a use for that > thing :) ) > > Do people have suggestions as to what to test for a primarily IMAP (+ > a little POP) server? I was thinking of doing something similar to > http://www.courier-mta.org/mbox-vs-maildir/ which selects a mail box, > deletes and expunges a message, fetches a few messages, and then does > some searches. > > Also, while I have the opportunity, are there any other benchmarks I > should run? I suppose I could compare dovecot with mbox vs maildir, > with indexing and without. Dovecot with indexing but the indexes > deleted, etc. I could compare dovecot to uw imap. > > Anything else? I probably can't justify the time to get cyrus up and > running. (I did that a few months ago when deciding which server to > use...) > > Ethan Sommer-- Trying to make bits uncopyable is like trying to make water not wet. The sooner people accept this, and build business models that take this into account, the sooner people will start making money again. - Bruce Schneier
Ethan Sommer wrote: [various RAID benchmark results] Which RAID10 where you using exactly, RAID1+0 or the native Linux MD RAID10 format? (see "man md" or http://en.wikipedia.org/wiki/RAID#Linux_MD_RAID_10 ) Because using the far (or offset) layout will quite dramatically influence the results. Regards, Christian Balzer -- Christian Balzer Network/Systems Engineer NOC chibi at gol.com Global OnLine Japan/Fusion Network Services http://www.gol.com/