Re: Realistic drive arrays

• From: "John Fullbright" <fullbrij@xxxxxxxxxxx>
• Date: Tue, 31 Jan 2006 17:02:18 -0800

Delivery to pst doesn't save anything.  You're just moving mail from managed 
storage to unmanaged storage and creating even more headaches.  In addition, 
because you delete the mail as soon as you get it, you double the churn on 
your log files and increase the duration of online maintenance.  Then some 
users will figure out that the pst on the desktop isn't backed up, and put 
it on a file server.  Of course this puts it back in managed storage, just 
shifting where, and increased network bandwidth consumption and client 
response times in the process.  It really is an ugly downward spiral.  If 
there's a business justification to keep the mail, keep it in Exchange.  If 
you have regulatory retention requirements that go beyond this, look at an 
archiving solution.


"Missing Link" <MissingLink@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message 
news:88796082-D5EB-4CC7-A867-27568171371D@xxxxxxxxxxxxxxxx
> Thanks again, I am going to push for the 6th drive and use 3 mirrors. 
> There
> may be an opportunity to swap 2 of the disks for a pair of 143Gb drives 
> from
> another server. To reduce the tendancy of the databases to grow I am going 
> to
> instigate mailbox restrictions and look at mail archiving outside of the
> Exchange system to allow me to force users to maintain their mailboxes
> properly. This also reduces the need for most users to have large personal
> folders.
>
> I am a bit cautious as my current 2k system has a 14Gb database set 
> despite
> the use of pst files, one user has overfilled 3 already.
>
> "John Fullbright" wrote:
>
>> Another option in DR situations is a USB drive on hand.  I's rather use a
>> USB drive than redirect to a share.  A local drive is alway optimal.
>>
>> RAID 5 with three disks is really a bad choice.  Write performance is 
>> 85*2/4
>> or 42.5 IOPS.  Read performance is 85*2 = 170 IOPS.  For a mixed load 
>> with a
>> 2:1 R/W ratio, 126.225 IOPS.  If you go with RAID 5, you need a lot of
>> spindles to get the write performance up to an acceptable level.  You get
>> the same performance with far fewer spindles with RAID 1/10/0+1.  A 
>> mirror
>> is 100% redundant.  Without a hotspare, you would have to weigh the risk 
>> of
>> two drives in the same mirror failing within the parts replacement SLA of
>> your hardware vendor.  In practice, the chance of this happening in say 
>> an 8
>> hour window is very remote. Of course, the longer you wait to replace a
>> failed drive the higher the probability of a second failure occurring 
>> will
>> become.  What about ordering an extra drive and having a spare on the 
>> shelf?
>> I'd recommend an analysis of your risk mitigation options.
>>
>> How much memory the store.exe process uses really depends on how much 
>> memory
>> you have installed.  Store, of course, isn't the only exchange process 
>> that
>> uses memory.  With the /3gb switch, each user mode process can have an
>> address space of up to 3GB.  Inetinfo, where smtp lives, consumes memory, 
>> as
>> well as other exchange processes.  Then there's Anti-virus, backups, and 
>> any
>> other process running on the server.  It's hard to say how much memory 
>> will
>> be used without very specific information on what's loaded and what the 
>> load
>> is.  It's easier just to measure with perfmon.
>>
>>
>>
>>
>>
>>
>> "Missing Link" <MissingLink@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
>> news:233D83F4-3C19-45E1-B82E-36EAB7602573@xxxxxxxxxxxxxxxx
>> > Thanks for that, a triple mirror set was one of my considerations
>> > particularly on the servers I have specified. One of the problems I 
>> > have
>> > is
>> > that two of the servers only have 5 36Gb drives. I didn't specify these
>> > ones
>> > myself and I can get a 6th drive in to do the triple mirror setup but I 
>> > am
>> > concerned about only 36Gb in a DR situation where I may need more than 
>> > one
>> > copy of the database on the disk. As an alternative I was going to 
>> > mirror
>> > 1
>> > pair for the logs, raid 5 with partitions using 3 disks for the rest 
>> > which
>> > gives some redundancy then define the 6th drive as a hot swap spare for
>> > both
>> > arrays. I know this does not give me the performance of a mirror but 
>> > does
>> > increase the contiguous disk space available, given the number of users
>> > and
>> > that few of them are heavy mail users performance should not be an 
>> > issue.
>> > With adequate memory how much does Exchange make use of the swap file?
>> > I would rate the I/O capability of this as of equal to the logs.
>> >
>> > "John Fullbright" wrote:
>> >
>> >> Three mirrors, excellent answer.  I would add, you could create
>> >> additional
>> >> partitions on Physical disk 0 for the bulk of your page file, and the
>> >> system
>> >> temp director and smtp queues.  This doesn't do anything for IO load, 
>> >> but
>> >> does help reduce fragmentation.
>> >>
>> >>
>> >> "Hobdey" <Hobdey@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
>> >> news:ACA9B76B-7DAC-4148-8575-4F82D324F07A@xxxxxxxxxxxxxxxx
>> >> > Personally with the 6 drives in question, I would run 3 mirrored 
>> >> > sets:
>> >> > 1
>> >> > for
>> >> > the OS and Exchange executables (also leaving the default SMTP
>> >> > directories
>> >> > on
>> >> > this set), 1 for the data stores (EDB and STM files), and 1 for the
>> >> > database
>> >> > log files.
>> >> >
>> >> > Even if you don't go that way, make certain you mirror your OS
>> >> > partition
>> >> > because even though there's not much activity there, a disk loss 
>> >> > would
>> >> > be
>> >> > a
>> >> > serious pain to recover from.  Plus, as I alluded to, the default
>> >> > location
>> >> > for the SMTP queue directories is on that partition as well and 
>> >> > there's
>> >> > a
>> >> > fair amount of activity there.  I wouldn't do anything with RAID 5 
>> >> > in
>> >> > your
>> >> > situation because you don't have the disks to spare.
>> >> >
>> >> > "Missing Link" wrote:
>> >> >
>> >> >> I am looking for documents giving realistic recommendations for 
>> >> >> drive
>> >> >> array
>> >> >> configurations for exchange server 2003 for and organisation with a
>> >> >> maximum
>> >> >> of 150 users per server in a distributed network Many that I have
>> >> >> found
>> >> >> give
>> >> >> proposals that require at least 8 drives, one if you followed it
>> >> >> through
>> >> >> wanted 22!!
>> >> >>
>> >> >> Both Dell and HP sell servers that have 6 drives, what is the best 
>> >> >> way
>> >> >> to
>> >> >> split these up for a mailbox server. The "Tuning Exchange Server 
>> >> >> 2003
>> >> >> Performance" chapter refers to an smtp bridgehead as using one
>> >> >> partition
>> >> >> with
>> >> >> mirroring if available. I would have split the single array drive 
>> >> >> into
>> >> >> a
>> >> >> number of partitions if only to reduce fragmentation, what does 
>> >> >> anyone
>> >> >> else
>> >> >> think. Is there any real benefit using a mirror for the O/S over a
>> >> >> raid 5
>> >> >> array as once it us loaded there should be little O/S activity in
>> >> >> comparison.
>> >> >>
>> >> >> Alan
>> >>
>> >>
>> >>
>>
>>
>> 


.

• Follow-Ups:
  • Re: Realistic drive arrays
    • From: Missing Link

• References:
  • Re: Realistic drive arrays
    • From: Missing Link

• Prev by Date: Re: Exchange Server Enterprise or Standard
• Next by Date: Re: EXch 2K3 SP1 and SP2 coexist - tough one
• Previous by thread: Re: Realistic drive arrays
• Next by thread: Re: Realistic drive arrays
• Index(es):
  • Date
  • Thread

• Windows
• Science
• Usenet

• Archive
• About
• Privacy
• Search
• Imprint