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12 'SAS' vs 24 'SATA' on DELL PowerVault MD3220i iSCSI SAN

Posted on 2010-09-21
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Would having double the SATA drives provide realtively the same IOPS as the SAS Drives?  We're looking to cluster a Hyper-v Environment with an Exchange 2010 vm and several database servers VM's.  Below are more specifics on the drives we're looking at.  We're just hoping someone else with some more experience can offer their suggestion.  I'm not sure of the latency and cache, etc... on these drives.  Our reasoning for thinking that the SATA drives would be nearly equal is because the qty of the drives is double (and cheaper) and with more drives to stripe to that the performance would be good.


In a RAID 60 Array...

24 x SATA 7.2K 500GB 6Gbp/s

-or-

12 x SAS 15k 600GB 6Gbp/s

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Question by:prentcorp
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alimoore earned 144 total points
ID: 33726201
Am I assuming you are taking the 12x SAS as the benchmark and trying to get the SATA array to compare speed wise so to save cost?

Have you also considered the other implications: ie error correction/detection, failure rates etc.
Does power consumption and heat enter the equation?
Does the iSCSI interface you are using provide enough bandwidth to make this question relevant?
What are you looking for: total IO, random read/write performace, or just general speed?
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Author Comment

by:prentcorp
ID: 33726333
Your first part is correct.  Saving cost and getting almost double the space.

error correct/detection had not crossed our mind, any insight you can share on that?

Power/heat is not an issue.

We will be running load balanced gigabit ethernet using LACP and 4 independent connections between each controller, switch and server to provide roughly 4Gbp/s of bandwidth.

Best performance for read/write I'd say.
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Assisted Solution

by:alimoore
alimoore earned 144 total points
ID: 33726527
ftp://download.intel.com/support/motherboards/server/sb/enterprise_class_versus_desktop_class_hard_drives_.pdf

Read the section: 1.1.4.1 Bad Sector Recovery, says it better than I could.

Your total transfer rate would be similiar, if not quicker with SATA but your random IO would be lower due to latency.
Given your setup, if you are looking for reliability and speed for database applications then SAS can't be beat (except for FC...)
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Author Comment

by:prentcorp
ID: 33726665
Referring to your Intel link; is it possible that the SATA drives are "enterprise class"?
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Assisted Solution

by:aleghart
aleghart earned 72 total points
ID: 33727207
There are "enterprise class" SATA drives that have longer MTBF and similar failure rates.  The timeout or unresponsiveness to the controller are also addressed.  Desktop-level drives will try to recover from a bad sector read, and may ignore the controller...leading the controller to believe the entire spindle is down, not just busy re-reading for lost data.

In an enterprise RAID, missing data can be better recovered from parity data versus re-reading the same spot multiple times.

Here is a quick take on Seagate's 3.5" enterprise drives.  Far right column is their SATA drive, which actually has SATA and SAS connection, but not fibre channel.
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Expert Comment

by:andyalder
ID: 33727721
There's a graph at http://www.dell.com/downloads/global/products/pvaul/en/powervault-md3200-nearline-sas.pdf which compares the near-line SAS with the equivalent SATA (they have the same HDA but different logic board). Both SATA and SAS flavours of the Baracuda ES.2 feature something called workload manager which if the drive gets hot puts it into read after write mode which really cripples performance but allows 24x7 operation. Without workload manager or a similar when they get hot they die quite quickly which is one reason why desktop drives aren't usable.

Assuming they aren't going to get hot then you will get about the same performance, perhaps a bit less since 7.2K disks are about 1/3 the IOPS of 15K SAS.

http://support.dell.com/support/edocs/systems/md3200i/en/matrix/matrix.pdf lists the supported drives, not the bit about having to buy from Dell or the MD3220 will refuse to play with them. (you can't even use ones with LSI or IBM firmware on even though the box is made by LSI logic.)
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Assisted Solution

by:kevinhsieh
kevinhsieh earned 142 total points
ID: 33730150
I think that either way you should have enough IOPs, which is really what you need. I use Dell EqualLogic, and started with 14 drive (12 active drives + 2 hot spare) Running about 25 VMs including Exchange 2003, file server, AD, BlackBerry Enterprise Server, SQL, and IIS for 450 users. Those are 750 GB 7200 RPM SATA drives in RAID 50. I am now using two arrays, so I have 24 drives and I can do 200 IOPS, but my during the day usage is around 900-1200 IOPS. My environment is bigger than yours.

I am looking at the configuration page, and it looks like the 3220i only does SAS, so it's a question of 7.2K, 10K, or 15K drives. I don't see 600 GB SAS drives in the 2.5" drive size, are you looking at the MD3200i?

I would start with 7.2K SAS drives, and add more if you need them. Are you ever looking to replicate to another site? Have you considered the Dell EqualLogic PS4000? It's just like the rest of the line in terms of performance but has a cheaper entry point.
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Expert Comment

by:BigSchmuh
ID: 33905878
I would rather go with a mix of :
-Good SSD (Crucial RealSSD, OCZ Vertex 2, Intel's) for IOPS intensive needs
-Enterprise class SATA 2.5" 500GB (Seagate Constellation, etc) for SPACE needs

Reading this Anandtech "SSD versus Enterprise SAS and SATA disks" article
   http://www.anandtech.com/show/2739/11
you can expect 1x SSD to support the same IOPS than 12x SAS 15k drives

Budget:
-16x 500GB SATA drives : 16x $300 = $4800 for 4TB in RAID 10
-4x 256GB Crucial RealSSD C300 : 4x $550 = $2200 for 512GB in RAID 10
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Assisted Solution

by:andyalder
andyalder earned 71 total points
ID: 33906134
There's only one SSD on the list BigSchmuh -
2.5" X1MCH LB150S 149GB SSD Pliant

Is that SSD any good?
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Expert Comment

by:BigSchmuh
ID: 33913238
Pliant LB150S is an EFD (Enterprise Flash Drive) with very impressive features:
   # IOPS: 120000
   # Data throughput (read/write): >420/220 MB/s
   # Full duplex, dual-port SAS interface
   # Write cache-less design eliminates data loss on power interruptions
but the Dell price for it is going to be a non-sense as usual with Dell's drives

I thought that one was able to replace those unbelievably pricey Dell's drive by any other drives, isn't that possible or is it a service problem ?
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Assisted Solution

by:kevinhsieh
kevinhsieh earned 142 total points
ID: 33915756
My $0.02 is that looking at putting unsupported 3rd party SSD into a MD3000i is a bit overboard given the fact that in all reality, 6-8 15K SAS or 12 SATA drives would provide all the IOPS required, and 12 SAS or 24 SATA drives is already overkill given the requirements as given. I haven't heard anything about large ERP databases, data warehouses or a VDI infrastructure. If any of those were part of the mix, I would hope that the author isn't looking at MD32XXi to begin with.
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Expert Comment

by:andyalder
ID: 33916231
MD3000 etc are OEM'd from LSI Logic and they key the firmware, you can't even put drives with LSI firmware in Dells, or Dell firmware drives in IBM enclosures etc and of course you can't flash them with the right firmware unless they are from the right vendor in the first place.
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Assisted Solution

by:BigSchmuh
BigSchmuh earned 71 total points
ID: 33921300
So it's time to get out of those overpriced basic storage box...

I quoted an equivalent here (in EUR for France) at 50% the Dell price (MD3220i + 18x 500GB SATA + 6x 150GB SSD Pliant LB150S + 3y 24/7 8H service)

Assuming the LB150S has "only" 12x more IOPS than a SAS 15k (which itself has 5x more IOPS than a SATA 7200rpm), I tried some Dell budgets :
-24x 600GB SAS 10k = $40.9k for 24x 200 (=4800) IOPS and 7.2TB mirrored
-24x 146GB SAS 15k = $27.2k for 24x 400 (=9600) IOPS and 1.8TB mirrored
-20x 500GB SATA + 4x 150GB SSD = $39.4k for 20x 90 + 4x 4800 (=21000) IOPS and 5.3TB mirrored
==> If you need more than 5TB mirrored, you have to go with 24x 600GB SAS 10k...otherwise, the 20x SATA+ 4x SSD will offer a lot more IOPS than all other mix (but you need to choose carefully whose data are to stay on the 300GB SSD array)
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Expert Comment

by:BigSchmuh
ID: 34518373
Sorry about that...but, to my opinion, the discussion lead to valuable info that should be shared through EE.
"No solve" is an information as well...
You should PAQ the question instead of deleting it.
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