Re: changing the exchange structure
- From: Elbryyan <Elbryyan@xxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Wed, 5 Sep 2007 07:06:06 -0700
My idea was to create 4 (three new) storage groups and create new stores
under each one, the goal being to reduce the size of the database store and
iplement size restrictions to prevent it from hogging all drive space. Since
our company is now going to a regional structure I was going to create a
storage group for each region and move the corresponding mailboxes to the
region to which they belong. I guess this would in essence create four
seperate instances of log transactions on the same disc which would probable
slow things down then. With that being said then the best case would be to
create multiple mailbox stores under the storage group to reduce the size of
the database? Is 100GB too large?
"John Fullbright" wrote:
To answer the first question, it depends on how you do it..
If you simply add another store in the same storage group, you achive a
smaller store size. You do lose some amount of single instance of storage,
and the amount of contention for the logs remains about the same.
If you create another storage group, and put the new store there, then you
achieve a reduction in store size as in the first option. You do lose some
single instance of storage as in the first option. The difference is that
each storage group has a unique set of logs. If half your users are on each
storage group, then contention for the logs will be reduced. This is an
important point in that writes to the logs are the most user visible aspect
of exchange IO.
If you take a moment to think about this, then the MS guidance on storage
group design in 2003 and recommendation of a 1:1 mapping of databases to
storage groups in 2007 makes sense; it minimizes contention for any given
set of logs. If you have increase the log buffers for each storage group,
then even in 2003 you should see some reduction in log write IO in that
there is less pressure on the log buffers and more opportunity to coalesce
IOs.
IO to the stores is essentially random. Placing two databases on the same
drive does not change that IO pattern. What is does do is increase the
potential for physical disk fragmentation. Is that a bad thing? Probably
not. Disk fragmentation negatively impacts sequential reads, but would have
minimal performance impact on a random workload. If you wanted to play it
safe anyway, you could create two logical disks on the same physical volume.
This trick will prevent the fragmentation by keeping the physical locaions
on the spindles seperate.
It's a whole different story with logs. Reads and writes to logs are
sequential. It's only during replay when multiple threads have log open
that you see anything different. If you place multiple sets of logs on the
same LUN, then the IO workload changes from a purely sequential one to one
that is something less than sequential. Performance will suffer. Whatever
you do with the databases, I'd keep the logs on seperate spindles.
The second question is a bit tougher.
You must have some sort of limit, otherwise you'll eventially hit the
physical constraint of available storage space and that's something you
don't want. You do have effectively a 1GB limit in place now. Deciding on
the right limit is going to take key stakeholders and management from your
organization getting together and deciding what the business requirements
are Is there a justifiable business need to have a 1GB mailbox? Only your
organization can answer that. The same goes for message size, number of
recipients, etc. What you can do is thake those requirements and, using
"Optimizing Storage for Exchange Server 2003" , show your organization how
the business requirement translates into a hardware/software requirement.
Do be aware that in order to have more than one mailbox store/storage group
in Exchange 2003 you'll need the enterprise edition.
"Elbryyan" <Elbryyan@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:4F2E2EEC-EE47-4AD4-91F2-E116D721E044@xxxxxxxxxxxxxxxx
I have a situation where I have single Exchange 2003 server hosting email
companywide. The storage group contains one mailbox store that is roughly
100GB in size which consists of roughly 300 mailboxes. We currently have
limits warnings to the user at 500MB and prevent sending of email at 1 GB
of
space. First question, if I create more stores on the server, will having
two stores on the same disk hurt performance? Transaction logs will be
located on a seperate disk as well but would then contain logs from
different
stores on the same drive. Hardware limitations would prevent me from
keeping
the additional stores and logs on seperate disks.
Second question would be, what is the general best practice on database
size
and or mailbox size restrictions. Currently the average mailbox size for
my
users is around 345MB. Thanks.
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