Hello all,
I have a few questions I hope you could answer.
I read the paper at
http://www.kierun.org/academic/lsm.pdf by Yann Golanski.
In that paper Yann recommends using a hard drive for the OS and a second
pair of drives (raid 1) for the spool as the spool drive will have very high
IO, and the system will need to access the exim binaries on the OS drive
often as well.
MEMFS or separate OS HDD questions:
1) Is the only reason for the separate drive for the OS to allow the exim
exe's to be read from a disk that is not busy?
2) What if instead I did the following:
Only 2 drives, raid 1 with OS and spool on them (boot, root, spool,
and swap partitions .. hopefully the swap will never be used). 1.5 GB ram.
When system is started a memory filesystem is created and the exim binaries
are copied into it. Also I plan on using Berkeley DB as the database for
the server, so I would copy the Berkeley DB into the memory file system as
well. Hints DB, etc are all in memory file system too. Exim is started
from the memory filesystem. Now anytime the exim binary needs to be used,
it is really just doing a memory copy and not accessing the OS partitions.
3) if #2 were used, how much of a hit would the exim logs make to the single
pair of raid 1 drives.... Is this another good reason to have a separate OS
drive? Or, maybe a separate drive just for the logs?
4) If instead of writing the exim logs to disk I sent log data to another
server via network would that (along with setup # 2) eliminate the need for
a dedicated OS drive in the server?
5) What do you think of using a setup similar to #2 + #4, but instead of
putting the OS on the HDD, you used a compact flash card (128MB or whatever)
to hold the OS and boot from? The idea here that a compact flash card
probably would be about as safe as a pair of raid 1 drives for the OS since
compact flash doesn't have any moving parts. The Berkeley DB for users, etc
would be pulled from the network at boot and held in memory. The hints
databases would be created fresh at boot and held in memory. Basically,
except for upgrades to software the compact flash would never be written to,
and only read during boot. Also no swap partitions anywhere... feedback???
6) What about network booting the SMTP servers, holding everything in RAM
like #2, and writing logs to network as in #4, no swap, and using the local
SCSI raid 1 drives just for spool?
-- topic #2 --
The setup:
Several SMTP servers running exim for in and outbound mail 10/100 connection
to internet
Several pop3 servers 10/100 connection to internet
Several file servers connected by a separate private 1Gb SWITCHED COPPER
network to the POP3 and SMTP servers
All servers are linux.
Which is better / faster NFS or SAMBA?
It really doesn't matter to me, I'll use either one. I've been searching
the web trying to find out which is faster (especially on a 1Gb network) and
which one is more reliable. Some reports seem to indicate that SAMBA is
faster and has lower overhead. Most of these report are for Win machines
using NFS clients to unix NFS servers. Others say NFS is faster.
1) So, which will have the most throughput for small (e-mail size) files?
2) I know with NFS the file server can go down and come back up and the
mount point will just start working again when the file server comes back
online. Will the same happen with SAMBA, or would it require an
unmount/remount to get things working again?
3) do you think a 1Gb network is overkill? Would a 100Mb switched network
be enough for:
10 SMTP / 5 POP3 / 5 file servers?
20 SMTP / 10 POP 3 / 10 file servers?
Suggestions on numbers?
Basically, if you were going to start from scratch, and wanted to build the
biggest, meanest, leanest, fastest, most mind blowing mail system going
while minimizing cost (2 drives in each server just for the OS raided can
get expensive) what would you do?
Thanks for the input.. It is very appreciated.
Rob
