Re: Add new cluster and use existing LUN's?

I am speaking from experience here: spindle contention can big the BIGGEST
bottleneck to a SQL installation. Recommendation, be careful. I think you
are on the right track though. A few points to help guide you.

1. A physical spindle (real disk) has limited IOPS and bandwidth capacity,
anywhere between 75 and 150 IOPS (I/Os per second) theoretical maximum
sequential reads. Random reads and any type of writes decrease from there.
To overcome this limitation, Meta-volumes are constructed out of the RAID
sets/Hyper-volumes.

2. Whether or not these RAID sets from which you construct the Hyper and
Meta-volumes are dedicated to a single host, single activity (OS, swap file,
TLogs, Data Files, or TempDB) or shared among many hosts with similar or
varied activity (DBMSes, Messaging Server, File Server, Web Servers,
Application Servers, or Middleware components), the physical spindles retain
the same theoretical IOPS and bandwidth capacities. Make sure what you
construct can handle the anticipated loads: both in IOPS and total
throughput.

3. The various activities of all hosts as well as those of a particular host
need to be isolated: O/S, page file, Quorum, MS DTC, TLogs, Data Files,
TempDB, Exchange Server jet files, Web Server pages, etc. You could
however, create a large RAID set that could be shared across multiple hosts
from which you construct several Meta-volumes that are dedicated to, say,
page file space. The point is ISOLATE the TYPE of activity, then share with
as many hosts as the IOPS and bandwidth will support.

4. Some of the physical spindle limitations can be addressed through the SAN
cache, which can be configured fractionally as dedicated to Read and or
Write operations. This piece requires a detailed understanding of the SAN
configuration and the anticipated host activity, whether or not that
activity has been made homogeneous throughout the SAN or whether or not the
various activities have been segmented to dedicate RAID sets.

5. Consider the number of SAN fibre controllers and available ports, each
one has a theoretical limit that can be overloaded and the number limits the
total activity that can be assigned to a given SAN cabinet installation.

6. Network switches, each port and switch have theoretical limitations and
which will be serving up all connected hosts. The total usage must be
aggregated to properly configure.

7. HBAs on each host have limitations. Even if you go through all of the
trouble of isolating activity on the SAN, carving up and presented isolated
LUNs to each host dedicated to the separate activities, if you try to run
all of that through one or two HBAs, you may still cause the same sort of
contention. Seriously consider running Windows 2003 and using STORport
drivers over SCSIport minidrivers. You will also need to look into a MPIO
solution like Veritas Volume Manager or EMC Power Path. This will allow you
to leverage the bandwidth across all HBAs and allow you to get by with fewer
overall, not to mention this will provide you another
Single-Point-of-Failure isolation.

8. Finally, I've already said it, but it so important that I'm going to say
it again. Many engineers only aggregate and examine total bandwidth real
and/or anticipated consumption, in the components, networks, or storage
solutions. That is, size capacity and throughput. How much data do I need
to store and how much do I need to transfer per second. However, for a
heavily used OLTP system, size is less important. Number of concurrent
transactions, and thus IOPS, will be the limiting factor. I don't know how
many times I have asked my sub-system engineers to look into either the
network or storage components just to have them come back and tell me I am
only using 10% of the bandwidth or total storage capacity. To which I
respond, I am running over 1,000 TPS and up to 1,000,000 IOPS. The typical
response is "Huh?". Which is never a good response to hear in a crisis
situation.

Hope this helps.

Sincerely,


Anthony Thomas


--

"skyline" <skyline@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
news:9993F283-E654-4F30-8316-E491670CCF35@xxxxxxxxxxxxxxxx
> I don't have access to the tool you mentioned but will research it
(Dell/EMC
> is correct by the way). I still have the fear of affecting performance on
> both virtual servers by forcing them to share the same 4 disks because
RAID
> 10 is not even bulletproof enough to gurantee a good speed if we are high
on
> the disk I/O side. I didn't want to semi-blindly make a decision to
purchase
> another cabinet and additional drives...hence why I came out here looking
to
> see if a few MVP's reccomended against it. I figured real world
experience
> may help me in the decision.
>
> Like I told Rodney, I know testing is in store for us--a smoking gun for
the
> decision. All I have now are my own opinions and reservations and that
isn't
> enough to guide my decision to spend or not spend money.
>
> Thanks for the advice.
>
> "Geoff N. Hiten" wrote:
>
> > Even a SAN has a maximum I/O capacity. Whether you are I/O bound on the
> > disks in question will determine whether using the remaining space will
> > impact your current system performance. Your SAN vendor (EMC from the
hints
> > you dropped) should have tools (likely for an additional fee) that can
> > measure IO at the LUN/RAID set/disk level. You will definitely need
that
> > capability in order to measure the impact of your proposed change. A
quick
> > test would be to run a simulated SQL I/O load on the newly created LUNs
> > while monitoring I/O performance at the SQL, OS, and SAN levels. Do the
> > same without the load and see how much you can get away with.
> >
> > Personally, I prefer to use LUNS that map one-to-one to RAID Sets,
mostly to
> > avoid this problem. Since that isn't a real option now, you may want to
> > consider purchasing an additional drive tray. It isn't the cheapest
> > solution, but it may be the most effective.
> >
> > BTW, you can share a LUN with more than one server. That is how a
cluster
> > is built. Access Logix whines about it but you can force it to do what
you
> > need. .
> >
> > --
> > Geoff N. Hiten
> > Senior Database Administrator
> > Microsoft SQL Server MVP
> >
> >
> > "skyline" <skyline@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
> > news:DA48AC82-6A9F-4738-BDB6-08D10D16EAB4@xxxxxxxxxxxxxxxx
> > > The SAN is indeed capable. Creating a LUN out of the 225 GB of
> > > unformatted
> > > data and assigning it to the new SQL server storage group is quick and
> > > easy.
> > > The first 5 drives of our SAN share the system binaries, Snapview
reserved
> > > LUN's, and 3 additional LUN's all set as RAID 5 (making a total of 509
GB
> > > divided between several different LUN's.) It is possible to share the
> > > same
> > > drives with more than one server, however you can't share one LUN with
> > > more
> > > than 1 server.
> > >
> > > However we would have 1 virtual server accessing the original LUN of
175
> > > GB
> > > and the other virtual server accessing the newly created LUN of 225
GB--my
> > > only hang up being the fact that the 2 LUN's exist on the same set of
4
> > > drives and if you have 2 completely independent SQL servers accessing
the
> > > same drives is it going to put a hurt on performance. Again, t-logs
stay
> > > seperate (IE the 2 virtual servers would not be sharing the t-log
drives,
> > > they would each have their seperate set of RAID 10 drives) so that is
my
> > > only
> > > saving grace thinking this implementation may be possible.
> > >
> > > I am here because I need a second opinion (and 3rd or 4ths if
possible)
> > > from
> > > some higher SQL guru's. I personally am the Net Admin so my SQL
> > > experience
> > > is not broad however I understand the concept of the SAN well and know
> > > what I
> > > am looking to do with the SQL servers.
> > >
> > > Thanks!
> > >
> > > "Rodney R. Fournier [MVP]" wrote:
> > >
> > >> It depends on the SAN. You may not be allowed to share the drives
with
> > >> different servers.
> > >>
> > >> Cheers,
> > >>
> > >> Rod
> > >>
> > >> MVP - Windows Server - Clustering
> > >> http://www.nw-america.com - Clustering Website
> > >> http://msmvps.com/clustering - Blog
> > >> http://www.clusterhelp.com - Cluster Training
> > >>
> > >> "skyline" <skyline@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
> > >> news:A4415101-D95B-4871-A666-4D4A2497275F@xxxxxxxxxxxxxxxx
> > >> >I realize that testing is the ideal way to come to the complete
> > >> >conclusion
> > >> >on
> > >> > our pathway but my first and foremost question really is has anyone
> > >> > successfully used a set of drives and have 2 luns for 2 different
> > >> > virtual
> > >> > servers on that same set of drives?
> > >> >
> > >> > I'd like to know if I am doing something "average" or if the
general
> > >> > consensus is against such an idea. That helps me to determine how
much
> > >> > of
> > >> > a
> > >> > possibility this really becomes and how much money I will be
spending.
> > >> >
> > >> > Thanks for your input thusfar.
> > >> >
> > >> > "Rodney R. Fournier [MVP]" wrote:
> > >> >
> > >> >> You need to stress test, look at the results, and then test some
more.
> > >> >> Testing will tell you what the correct answer is for your
environment.
> > >> >>
> > >> >> Cheers,
> > >> >>
> > >> >> Rod
> > >> >>
> > >> >> MVP - Windows Server - Clustering
> > >> >> http://www.nw-america.com - Clustering Website
> > >> >> http://msmvps.com/clustering - Blog
> > >> >> http://www.clusterhelp.com - Cluster Training
> > >> >>
> > >> >> "skyline" <skyline@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote in message
> > >> >> news:18DB25CC-37FC-4FEF-AF56-64696BE9D0B8@xxxxxxxxxxxxxxxx
> > >> >> > Hi All,
> > >> >> >
> > >> >> > We have a Win2003 Enterprise/SQL 2000 "active/passive" cluster,
and
> > >> >> > we
> > >> >> > want
> > >> >> > to split a few larger DB's off to a seperate and new
> > >> >> > "active/passive"
> > >> >> > cluster. The reason for the split is to allow this new cluster
to
> > >> >> > control
> > >> >> > the one application and the other cluster to control the
existing
> > >> >> > app.
> > >> >> > Currently we have:
> > >> >> >
> > >> >> > SQL LUN occupying 4 Raid 10 disks with 175 GB assigned to this
LUN.
> > >> >> > Doing
> > >> >> > the math leaves us with appx. 225 GB left on these 4 discs that
is
> > >> >> > unnassigned and unformatted.
> > >> >> >
> > >> >> > T-log/Quorum LUN occupying 2 Raid 10 disks with all of the space
> > >> >> > assigned
> > >> >> > to
> > >> >> > this LUN (appx 134 GB).
> > >> >> >
> > >> >> > We are most likely not going to utilize the entire 175 GB for
the
> > >> >> > data
> > >> >> > collection side let alone the additional 225 GB. At what impact
to
> > >> >> > the
> > >> >> > disk
> > >> >> > I/O are we going to suffer if we create the new a/p cluster
using a
> > >> >> > newly
> > >> >> > assigned LUN that occupies the previously unformatted 225 GB on
the
> > >> >> > SQL
> > >> >> > data
> > >> >> > disks? So essentially we would have 2 seperate virtual servers
> > >> >> > operating
> > >> >> > off
> > >> >> > of the same spindles, however 2 different LUN's. My gut feeling
> > >> >> > says
> > >> >> > that
> > >> >> > we
> > >> >> > would take some type of I/O performance hit since 2 seperate
high
> > >> >> > I/O
> > >> >> > applications are accessing the same spindles. We would however
have
> > >> >> > 2
> > >> >> > new
> > >> >> > RAID 10 disks for the t-logs and quorum of the new cluster and
since
> > >> >> > they
> > >> >> > are
> > >> >> > the highest I/O portion of SQL and would not be sharing this is
the
> > >> >> > only
> > >> >> > reason I think the idea may be feasible.
> > >> >> >
> > >> >> > The reasons for trying to use the unformatted space on those 4
> > >> >> > spindles
> > >> >> > is:
> > >> >> >
> > >> >> > A) The data collection app already running on those spindles in
the
> > >> >> > 175
> > >> >> > GB
> > >> >> > space is never going to use all of that space (it is using 50 GB
> > >> >> > currently
> > >> >> > and at least half of that is the other app we want to split
off).
> > >> >> > So a
> > >> >> > future of adding the 225 GB as a metalun to the existing SQL LUN
is
> > >> >> > slim
> > >> >> > to
> > >> >> > nill.
> > >> >> >
> > >> >> > B) We are hosed on that 225 GB of space for eternity really.
If we
> > >> >> > can't
> > >> >> > use it for another SQL cluster I don't think there is anyway we
> > >> >> > would
> > >> >> > use
> > >> >> > it
> > >> >> > for file storage for example. That is based on my opinion...I
have
> > >> >> > a
> > >> >> > hard
> > >> >> > time believing it is okay to add another set of SQL data let
alone
> > >> >> > file
> > >> >> > data.
> > >> >> >
> > >> >> > C) We only have 3 slots left in the first SAN cabinet. We will
be
> > >> >> > using 2
> > >> >> > of those for a RAID 10 t-log setup for the new SQL cluster so
that
> > >> >> > leaves
> > >> >> > us
> > >> >> > with 1 drive space open for the new SQL cluster data
> > >> >> > which=impossible.
> > >> >> > So
> > >> >> > now we not only have to buy additional drives but also a new
cabinet
> > >> >> > and
> > >> >> > all
> > >> >> > associated hardware.
> > >> >> >
> > >> >> > Keep in mind our main goal here is the processing power. Our
> > >> >> > existing
> > >> >> > cluster's processor is by no means outdated, but the data
collection
> > >> >> > AND
> > >> >> > reporting runs at the same time are causing slow downs due to
> > >> >> > processing
> > >> >> > requests from many different applications. If reporting were on
> > >> >> > it's
> > >> >> > own
> > >> >> > cluster that means it has its own server to beat up on and our
> > >> >> > clients
> > >> >> > don't
> > >> >> > notice delays in web surveys or IVR calls when the daily reports
are
> > >> >> > being
> > >> >> > aggregated.
> > >> >> >
> > >> >> > Any help provided is greatly appreciated.
> > >> >>
> > >> >>
> > >> >>
> > >>
> > >>
> > >>
> >
> >
> >


.

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