[THIN] Re: RAID 1

Well ? I knew you meant RAID0 when you wrote RAID1 and vice versa ? I see
what you did there, keep everyone on their toes and make sure we?re paying
attention. I see I?m not the first to comment, so I take it I?ve not won the
£5 L

 

My ?issue? is that for blades/1U servers (which is not an uncommon config
for a citrix/ts server) what *is* the performance difference for a
RAID1/RAID0/separate drives ? is it significant? 

 

Yes, technically, when you?ve multiple spindles you get a better performance
? but, what does that better performance relate to in the real world? You?ve
only two drives ? how much ?better? is ?better?? 

 

I would typically configured a RAID1 config as it?s the more reliable ? but,
what I?ve not had chance to do is take a couple of servers, build
raid1/raid0/separate drive configs and then load them up which performs
better. 

 

And then

 

Transactions or archives should not be kept on Raid 1.  RAID 1 should not be
used if the application?s ?presence? is not managed for you (Clustered VIP,
Farm) ?I guess I am saying, if the box goes down and you have another host
that is going to handle the load then you shouldn?t be afraid to use RAID 1
over 0.  

 

Yes ? that?s right and dandy for, say, a SQL or exchange backend ? but
perhaps that?s of little use to you if your citrix server goes off-line with
50 concurrent users. Punters may well be able to reattach on another server
in the farm ? but only after they?ve hunted you down and maimed you with a
rusty spoon as they?ve lost the end of year financial data they were working
on at the time? yet ?is the risk of that happening worth taking given the
(possible) performance increase that you?ve gained by dropping raid1 and
using raid0?

 

I?m more than willing to accept a short contract for me to muck about with
this and bring back findings if anyones interested J

 

From: thin-bounce@xxxxxxxxxxxxx [mailto:thin-bounce@xxxxxxxxxxxxx] On Behalf
Of Dupris, Mike
Sent: 30 April 2007 22:30
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: RAID 1

 

Raid 1 out performs Raid 0 but is riskier because of the lack of redundancy.
Raid 1 is better best used for basic ?stuff? that you can easily get back on
due to failure (NOS, easy applications quickly installed) ?think if you can
rebuild it from disk (or blast down from an image) then do a basic restore
of a limited amount of settings or configurations (from file) and your
operation is back up and running then RAID 1 is better for performance.

 

Raid 0 is delayed because of the read & compare then delete & writes.  Raid
1 spreads data across disks thereby spreading out the disk operations across
the array (relieving bottlenecks.)

 

Temporary files and system pagefiles can be kept on a single independent
disk (rather than the same disk ?remember we are trying to limit the times
we have to wait on the arm to position the head on one of the platters ?for
the matter, we are also wanting to remove overhead on an array controller.)
Risk:  if that disk the temp/system file is located on fails during
production, that could cause a serious issue if your system relies upon
heavy pagefile use. 

 

Transactions or archives should not be kept on Raid 1.  RAID 1 should not be
used if the application?s ?presence? is not managed for you (Clustered VIP,
Farm) ?I guess I am saying, if the box goes down and you have another host
that is going to handle the load then you shouldn?t be afraid to use RAID 1
over 0.  

 

Here is a high performance production setup for Clustered or Farmed boxes

 

[NOS] 3 disks, raid 1, controller A, disk cache enabled, PCI bus X (I like
at least 3 for dedicated OS ,volume -single patrician)

[TEMP] 1 disk, independent disk, disk cache enabled, controller B, PCI bus Y

[DATA] Multiple disks, raid 5 or 10, disk write-through if Database,
controller C or SAN attached, PCI bus Z or SAN attached

 

Where XYZ are placeholders for whatever dedicated PCI buses are available on
your system. 

 

Mike Dupris

 

From: thin-bounce@xxxxxxxxxxxxx [mailto:thin-bounce@xxxxxxxxxxxxx] On Behalf
Of Andrew Wood
Sent: Monday, April 30, 2007 7:45 AM
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: RAID 1

 

I?ve always wanted to do this but never had the time ? it?d be interesting
to note what the performance gain was in relation to the fact that you
increase your risk of causing an outage due to a single disk failure?

 

From: thin-bounce@xxxxxxxxxxxxx [mailto:thin-bounce@xxxxxxxxxxxxx] On Behalf
Of Joe Shonk
Sent: 28 April 2007 15:38
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: RAID 1

 

It's a very interesting question indeed.   Which blades are you using?  What
kind of i/o controller?

Putting the pagefile (alone) on a second partition will help performance
with regards that the pagefile will be create as one large continuous(non
fragmented) file. 

With some controllers (those with NO cache), you can see an increase in
performance by not using RAID 1 and have two independent spindles and put
the pagefile, temp dirs, and spooler on the second drive.  But if you are
going to do that, then why not set it up a RAID 0 with a second partition
for the pagefile.  We literally 2x the performance in reads and writes with
the configuration over RAID 1. 

Joe

On 4/27/07, Charles Watts <gregwatts77@xxxxxxxxxxx> wrote:


We are using HP Blades with RIAD 1 for our Citrix Servers on Windows Server
2003 SP1. My question is would we get better disk i/o performance if we
partioned the RAID 1 into two partitions and stuck the page file, temp 
directories and programs on the second partition? If not has any one used a
RAMDISK for this? Or is their an argument for eliminating RAID 1 altogether
and just put the page file, temp directories on the second hard drive 
(better performance and more disk space). Since I have a boat load of blades
where is the risk? So I lose one or two drives a year on my servers and each
time 50 - 60 users get kicked off. heck! I do that accidently at least once 
a year!?  Managment might not buy that argument but If the performance gain
is significant then it's worth it. Your thoughts?

Thanks,

Greg


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