San Performace settings SQl Server

hi everyone,
Am presenlty Testing the I/o performance on the new CX-500 San From Emc
And Hba From Emulex,The LUn Size is 1 TB and when doing the Testing
with SQlIO Tool with a I/o block size-8 i get 39.3
MB/sec for Random write requestes but when doing the same with Random
Read
requests i get 6.04 MB/sec as the output,the read/Write cache is
enabled with read cache set to 288 and write to 1198,We have a
sqlserver Oltp Enviroment with mostlty Read Intensive Operations , iam
wonering how can i increase the Read i/o ,The Lun design looks bad we
should have made smaller Luns and Shared the Data and Log Files among
them ,will i get any performance if i set read cache to low value or
turn off the read cache or should i recomend to rebuild the san design
to smaller chunks , i am not so well versed in san
design , what i want is best perfromance for my sql serverr IO ,Pls
Suggest
Thanks,
SaradhiI will be beneficial if you spread the Data, T-Log and TempDB files
across mutilpe LUN's as opposed ot a single alrge LUN and additionally
invest in a 2nd HBA so you have multiple channels to the SAN.
If your environment is Read-intensive then logic would dictate biasing
the cache towards Read operations as opposed to Write, you might be
better making small adjustments and re-testing until yo ustrike a happy
medium.
ALI|||It will be beneficial if you spread the Data, T-Log and TempDB files
across multiple LUN's as opposed to a single large LUN and additionally
invest in a 2nd HBA so you have multiple channels to the SAN.
If you have tools to identify hot spindles then so much the better as
you can then try distributing the high-usage elements.
If your environment is Read-intensive then logic would dictate biasing
the cache towards Read operations as opposed to Write, you might be
better making small adjustments and re-testing until you strike a happy
medium.
ALI|||u had any performance increase by increasing the Read cache,Any Reads
Done will be checked In the sql Buffer cache else will go for a disk
read and ihave set the max server Memory to 12 gb out of 16, Does Read
cache in the
helps us in improving the Read I/o operations as i have read in some of
the postings in here not to go for Read cache but to turn off the read
cache and read ahead and use all for write cache ,As u suggesst should
i check the Io By
increasing the Read cache and check the stats
Thanks&Regards
saradhi

SAN Array setup

Our server team has set up an EMC Clarion SAN with 3 sets of RAID 5 arrays,
several RAID 1 arrays and other drives/arrays for snapshots. The first
server we are installing has the data going to an 80 GB slice an an 8 disk
RAID 5 array and the logs going to a 20 GB slice on a 5 disk RAID 5 array.
Eventually, several other database servers will be added to this SAN.
The first server will hold several small databases and one or more large
databases, all totaling 20 - 50 GB. Some of the large databases will be
replicates from other servers. I assume the replication will be
transactional with non updateable subscriptions. Some of the databases will
also replicate to other servers. I assume the replication for these will be
transactional with updateable subscriptions. All databases will be serving
up content for web applications.
Does anyone have experience using RAID 5 on an EMC Clarion for the log
files?
I do not know how much data will be replicated and I don't have any stats on
the servers the app was developed on. Would anyone hazard a guess as to the
MB/hour of data that may overwhelm this RAID 5 data volume?
Any educated opionions are welcome, especially if you can back it up with
some examples etc.
I avoid RAID 5 at all cost. See http://www.baarf.com/ if you are bored and
wanna read some experiences, horror stories, sillies, rants, etc..
That said, the nature of your application plays a huge role in the decision
on what RAID configuration. Stripping with parity is probably "ok" if you're
doing mostly reads and have solid backup and maintenance processes in place
(eg. swap out disks before MTBF). However, if all all possible, put your
data on a RAID 1+0. Yes, quite a bit of extra cost involved but if you're
paranoid about simultaneous disk failures and/or have high performance
requirements, definitely worth considering. I've done this stuff for 15
years and have only seen 1 CPU failure ever. I have seen a good number of
multiple drive failures either simultaneously or very close to each other.
There were 2 occurrence of a second drive failing shortly after a
replacement drive was stuck into the array and rebuilding had only just
begun. Good thing we had backups.
Transaction logs are perfectly happy sitting in its own disk or mirrored
disk for availability. I would not recommend RAID 5 for your logs. It's just
an unecessary performance hit (tlogs activities are sequential) plus it'll
use up more physical drives than a mirror anyway.
One thing you want to be careful with is what the SAN administrators are
really giving you when they assign you a LUN. There's a lot of black magic
inside a SAN box and I have met many SAN vendor reps that insist it doesn't
matter if we're getting a "slice" of an array or our own array because the
big caches. These guys obviously have not had to work with high transaction
environments with multiple workloads on the same SAN.
Btw, there are free tools available to stress your IO. See below for one
example from Microsoft.
http://www.microsoft.com/downloads/d...DisplayLang=en
joe.
"Dean" <deann@.dtn.com> wrote in message
news:%237z1llFFFHA.2460@.TK2MSFTNGP09.phx.gbl...
> Our server team has set up an EMC Clarion SAN with 3 sets of RAID 5
> arrays,
> several RAID 1 arrays and other drives/arrays for snapshots. The first
> server we are installing has the data going to an 80 GB slice an an 8 disk
> RAID 5 array and the logs going to a 20 GB slice on a 5 disk RAID 5 array.
> Eventually, several other database servers will be added to this SAN.
> The first server will hold several small databases and one or more large
> databases, all totaling 20 - 50 GB. Some of the large databases will be
> replicates from other servers. I assume the replication will be
> transactional with non updateable subscriptions. Some of the databases
> will
> also replicate to other servers. I assume the replication for these will
> be
> transactional with updateable subscriptions. All databases will be serving
> up content for web applications.
> Does anyone have experience using RAID 5 on an EMC Clarion for the log
> files?
> I do not know how much data will be replicated and I don't have any stats
> on
> the servers the app was developed on. Would anyone hazard a guess as to
> the
> MB/hour of data that may overwhelm this RAID 5 data volume?
> Any educated opionions are welcome, especially if you can back it up with
> some examples etc.
>
|||Push back. We just went through the same issue with our local EMC technical
sales guy when we bought our CX-700.
It seems to me he tried to talk our SAN guy into going with a bunch of 4
drive RAID 5 arrays because he could show better MB/$ costs. His hope was
that they could make up for the RAID 5 overhead with their cache. When I
pushed back, he brought in their regional SQL Server specialists (that's how
they were positioned anyway). When we explained our throughput requirements
(the same ones we explained to our local tech rep), they both said, "You
need RAID 10".
"Dean" <deann@.dtn.com> wrote in message
news:%237z1llFFFHA.2460@.TK2MSFTNGP09.phx.gbl...
> Our server team has set up an EMC Clarion SAN with 3 sets of RAID 5
arrays,
> several RAID 1 arrays and other drives/arrays for snapshots. The first
> server we are installing has the data going to an 80 GB slice an an 8 disk
> RAID 5 array and the logs going to a 20 GB slice on a 5 disk RAID 5 array.
> Eventually, several other database servers will be added to this SAN.
> The first server will hold several small databases and one or more large
> databases, all totaling 20 - 50 GB. Some of the large databases will be
> replicates from other servers. I assume the replication will be
> transactional with non updateable subscriptions. Some of the databases
will
> also replicate to other servers. I assume the replication for these will
be
> transactional with updateable subscriptions. All databases will be serving
> up content for web applications.
> Does anyone have experience using RAID 5 on an EMC Clarion for the log
> files?
> I do not know how much data will be replicated and I don't have any stats
on
> the servers the app was developed on. Would anyone hazard a guess as to
the
> MB/hour of data that may overwhelm this RAID 5 data volume?
> Any educated opionions are welcome, especially if you can back it up with
> some examples etc.
>