[Dovecot] Best Cluster Storage

[Henrique Fernandes]

So i read all emails and stuff.

But  i am sorry to say, much of the things you said we are not able to do.

About change the EMC to raid 10, can not do it because other people are
using it. So we can not edit anything one strage. Those other luns i talk
about, they are ment to be for WEB but as we are testing we are allowed to
use it.

Much that you said, we are trying to do, but we don't have the hardware.

Our XEN just have 2  1gbE enterfaces, and we are using one for get external
and another one to use the storage ( ours vms is also in ocfs2 to be able to
migrate and etc to any host )

Anyway, we are considering very much the idea of making DLM on a dedicated
network. We gonna study some way to do it with or hardware.

Apreciate your help, i guess i lernad a lot. ( i did forward this emails for
some of my bosses, hope will change anything about hardware, but who knows.
)

Anotehr thing to say, the email is not very tunning yet, but as we gonna
improving we start to get more money to buy more stuff to the service. Thats
is we we try to make it better with poor hardware. AS i said, before it was
everything on fisica desktop with 500gb of disk. So right now we make a
really big improvement.

Thanks a lot to all, i still apreciate any help. I am reading it all and
trying to take the best of it!


[]'sf.rique


On Fri, Jan 21, 2011 at 8:06 PM, Stan Hoeppner <stan at hardwarefreak.com>wrote:

> Henrique Fernandes put forth on 1/21/2011 12:53 PM:
>
> > We think it is the ocfs2 and the size of the partition, becasue. We can
> > write an big file in a accetable speed. But if we try to delete or create
> or
> > read lots of small files the speed is  horrible. We think is an DLM
> problem
> > in propagate the locks and etc.
>
> It's not the size of the filesystem that's the problem.  But it is an issue
> with
> the DLM, and with the small RAID 10 set.  This is why I recommended putting
> DLM
> on its own dedicated network segment, same with the iSCSI traffic, and
> making
> sure you're running full duplex GbE all round.  DLM doesn't require GbE
> bandwidth, but the latency of GbE is less than fast ethernet.  I'm also
> assuming, since you didn't say, that you were running all your ethernet
> traffic
> over a single GbE port on each Xen host.  That just doesn't scale when
> doing
> filesystem clustering.  The traffic load is too great, unless you're idling
> all
> the time, in which case, why did you go OCFS? :)
>
> > Do you have any idea how to test the storage from maildir usage ? We made
> a
> > bashscript that write some diretores and lots of files and after it
> removes
> > and etc.
>
> This only does you any good if you have instrumentation setup to capture
> metrics
> while you run your test.  You''ll need to run iostat on the host running
> the
> script tests, along with iftop, and any OCFS monitoring tools.  You'll need
> to
> use the EMC software to gather IOPS and bandwidth metrics from the CX4
> during
> the test.  You'll also need to make sure your aggregate test data size is
> greater than 6GB which is 2x the size of the cache in the CX4.  You need to
> hit
> the disks, hard, not the cache.
>
> The best "test" is to simply instrument your normal user load and collect
> the
> performance data I mentioned.
>
> > Any better ideias ?
>
> Ditch iSCSI and move to fiber channel.  A Qlogic 14 port 4Gb FC switch with
> all
> SFPs included is less than $2500 USD.  You already have the FC ports in
> your
> CX4.  You'd instantly quadruple the bandwidth of the CX4 and that of each
> Xen
> host, from 200 to 800 MB/s and 100 to 400 MB/s respectively.  Four single
> port
> 4Gb FC HBAs, one for each server, will run you $2500-3000 USD.  So for
> about $5k
> USD you can quadruple your bandwidth, and lower your latency.
>
> I don't recall if you ever told us what your user load is.  How many
> concurrent
> Dovecot user sessions are you supporting on average?
>
> > Apreciate your help!
>
> No problem.  SANs are one of my passions. :)
>
> --
> Stan
>