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3 VA 7410 vs 1 EVA4400

El chupacambra
Occasional Advisor

3 VA 7410 vs 1 EVA4400

Hi all,
It is probably a stupid question, but my lack of experience makes me ask you.
Our Informix database (transactional database with lots of concurrent users and lots of I/Os)is using 5 volume groups spread across 3 VA 7410. The I/O performance of the 3 VAs is just enough for the database.
Could we replace the 3 VAs with just one EVA4400 in terms of I/O speaking?
Does it matter what size (for rpm we will use 15.000rpm disks) of disks will be used on the EVA? The available options are 146Gig or 72Gig disks.
Reading the specs I can see that each VA deliver 35.000I/Os per second and the EVA is around 140.000 I/Os per second if this help at all.
Please let me know if more info is needed.
Thank you in advance.
9 REPLIES
Uwe Zessin
Honored Contributor

Re: 3 VA 7410 vs 1 EVA4400

It is impressive how many I/Os a controller can do from cache memory when a special benchmark program is run, isn't it? ;-)

Of course you will NEVER see such numbers in a real-life environment. I recommend that you measure the read/write I/Os in YOUR environment and then size the number of disk drives to satisfy IOPS and total capacity - maybe with a bit of room to grow.
.
TTr
Honored Contributor

Re: 3 VA 7410 vs 1 EVA4400

Even comparing the 35.000 io/s of the VA7410 with the 140.000 io/s, you see that the EVA is barely more powerfull. 3xVA=105.000, 1xEVA=140.000. I don't think that is much of a difference.
On the other hand, how are your VAs configured right now? Are they fully loaded? How many trays and disks? If you are NOT using the full i/o power of each VA then the EVA might be OK for you. If you expect a lot of growth in the future you should definitely consider something more powerfull than the 4400. You should definitely go with the 15.000kRPM disks. The disk size does not really matter unless you need a lot of capacity. I would think that the 146GB disks are becoming more common these days.
El chupacambra
Occasional Advisor

Re: 3 VA 7410 vs 1 EVA4400

Hi again,
Answering your questions:
The VAs are working at their full capacity since are equiped with 30 36Gig 15K disks each. 85% of the available space is used by the database.
Also from performance (iops) point of view, are also performing on their operational limits.
If it helps both VAs and EVA have the same amount of cache memory per controller (2Gig).

Concerning the answers so far, I still don't understand if the EVA can deliver: the same less or more IOPS than the 3 VAs.
Thank you.
TTr
Honored Contributor

Re: 3 VA 7410 vs 1 EVA4400

Anyway you look at it it looks like it is going to be tight with one EVA4400.
How many disks are you thinking of getting with the EVA? The 3 VAs have 90 disks and the EVA can have at most 96 disks.

What size are the VA disks now?
How id your server connecting to the 3 VAs? With 2 fiber connections or with 6?

For performance you should get as many disks as you can but you use very little space on each disk. This way you rely very little on each single disk for i/o. The EVA can pump 1550MB's of throughput. That is probably in a setup as I just mentioned. If you get fewer disks of higher capacity you will NOT get anywhere near the 1550MB/s throughput.
Do you have any idea what is the throughput on your informix server today?

Another thing to consider is the number of back-end loops of the EVA4400. These are the fiber loops that go out to the disk drive trays and collect the data for the actual physical disks. The EVA4400 has 4 "device ports" per controller pair. This means that the EVA4400 collects i/o from the disks the same way that 2 (TWO) VA7410s would do. You may think that this is not enough. However if you consider that the 4400 runs at 4Gbit and you have a transactional database (many small i/os) that may be enough.

What about future growth? That is in capacity and i/o demand. If you expect a lot of growth the 4400 might not make it.
Uwe Zessin
Honored Contributor

Re: 3 VA 7410 vs 1 EVA4400

> the 4400 might not make it.

Well, maybe not. That is why I asked what the current throughput on the VAs is - it does not make sense to compare artificial numbers created with special benchmarks.

On the other hand: of course you can 'scale-out' the EVAs as well - e.g. use two EVA-4400 instead of one -8100.
.
TTr
Honored Contributor

Re: 3 VA 7410 vs 1 EVA4400

One other question to ask is can your server handle a faster disk array. Your current server may be in balance with th 3 VAs and adding a fast array to an old server may be a waste of the array.

> It is impressive how many I/Os a controller can do from cache memory when a special benchmark program is run, isn't it? ;-)

I liked that comment. I go through a lot of pain trying to explain to my folks here that you can not have the throughput and the capacity on an array at the same time.
El chupacambra
Occasional Advisor

Re: 3 VA 7410 vs 1 EVA4400

- The EVA is going to have 24x146Gig 15K disks.
- VA disks currently are 90x36Gig 15k
- The servers are 2xItanium rx7640 (in cluster) with 2 fiber connections per VA.
- I'm not sure how to mesure the Informix server throughput but I think that is around 8.000-12.000 IOPS and 30MB/sec.
- We don't care for future growth. We just want to see if we can replace the 3 VAs with just one EVA and have no performance degradation.
Thank you again.
marsh_1
Honored Contributor

Re: 3 VA 7410 vs 1 EVA4400

so the only upside you're looking for is the maint cost savings and supportability ?
have you no other storage pools that would benefit from consolidation - looking at HP's SVSP / low end XP or IBM SVC ?
It just seems a rather short term view.

maybe worth speaking to hp to see if there is any way you could 'try before you buy' in one of their test labs with your apps ?

fwiw
TTr
Honored Contributor

Re: 3 VA 7410 vs 1 EVA4400

The servers are powerfull enough. Base on your statement about future growth, one 4400 should be enough to replace the 3 VAs except one major point. Your new EVA has only 24 disks. Can you pump the amount of data that you do now out of only 24 disks? Regardles of how many LUNs you are going to create, the amount of data is going to come out of the same 24 disks. You should definitely spread out the data on more disks. I would consider at least 60 and maybe some more. At the same time you would not spread all your LUNs on ALL these disks, you would separate them in disk groups like you have now on the VAs (you probably have a total of at least 6 today on all the 3 VAs). Then you spread out your server volumes evenly on all the LUNs as much as possible. How many LUNs are you going to create in those 24 disks? Any i/o out of any LUN is going to come out of the same 24 disks (or 12 if you separate them to 2 groups).
You can buy the fastest disk array with many i/o channels, if you only install 12 or 24 disks in it, you can't do much i/o, can you.

> ... with 2 fiber connections per VA.
Is that through a SAN fabric or direct attached. If direct attached you have 6 FC interfaces on the rx7640s. Are you maintaining those or are you cutting down to 2?
Whether 6 or 2 server interfaces, with the EVA, all i/o will come out of the 2 controllers of the EVA regardless of the number of ports that you use, whereas now the i/o comes from 6 VA controllers.

You need to look at the entire spectrum of the data path
Server, server i/o channells, server FC ports, FC wiring (SAN), array controllers, disk groups, number of LUNs, number of disks. Then look at the LUNs, the server volumes and the database i/o files (volumes). A constrain in any of these areas can kill your whole environment.