gprdawson
2 Bronze

Re: 10k drives versus 15k drives: rotational speed issues

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I'm not surprised to see slower 10k 2.5" drives and faster 15k 3.5" drives.

The 15k 3.5" drives may well have same size or even smaller platters than the 10k 2.5" other things also affect the total size of the disk drive.

e.g To go faster a more powerful motor is probably required which will generate more heat which will need more cooling which will need more space.

A bigger drive also means bigger bearings can be used so the spindle does not wobble as much.

Personaly, I'd like to see 2.5" SSDs as a VNX5100 DPE with a mix of up to 25 2.5" drives providing FAST cache (on 2.5" SSDs) and a bunch of 10K SAS

would be a great replacement for my CX300!

RRR
6 Indium

Re: 10k drives versus 15k drives: rotational speed issues

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Allen, don't look at the cooling fins ! I couldn't find a picture of a case without them. If you have the opportunity to do the following: please do:

Grab a few old drives which are broken and open them up. The 10k drive is probably 3.5 inch and the 15k is 2.5 inch (at least, it's smaller).

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RRR
6 Indium

Re: 10k drives versus 15k drives: rotational speed issues

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So is there an EMC tech guy around who can answer my question if the 10k 2.5 inch / 15k 3.5 inch is a typo or that the 15k drives really hold 3.5 inch platters ?

I know the VNX documentation mentions the 15k 3.5 inch, but I'm pretty sure this is a typo....

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gprdawson
2 Bronze

Re: 10k drives versus 15k drives: rotational speed issues

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Here's am image of a Seagate Cheeta 300GB 15k SAS drive with the lid off.

http://www.64bit.eu/gallery/3583/seagate-cheetah-300gb-hdd-15k-sas-16mb-cache-detail.jpg

As you can see while the drive is 3.5" the platters are not. I've no idea if the platters would fit in a 2.5" drive.

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RRR
6 Indium

Re: 10k drives versus 15k drives: rotational speed issues

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I was questioning the paper I mentioned in my first post. Your comment is valuable, but I still have no answer.

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gprdawson
2 Bronze

Re: 10k drives versus 15k drives: rotational speed issues

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I think the 2.5" drives are slower due to packaging issues.

It might not be possible to pack a faster, more powerful, motor and handle its cooling requirements using the 2.5" drive form factor.

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RRR
6 Indium

Re: 10k drives versus 15k drives: rotational speed issues

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I don't mean the whole drive casing, just the platters

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RRR
6 Indium

Re: 10k drives versus 15k drives: rotational speed issues

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Ahhhh.... I see where I'm going in the wrong direction: the pdf states "form factor", so that's the drive casing ! So the VNX really can hold larger drive casings as well as smaller ? Do we need different DAE's to accomplish this ?

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gprdawson
2 Bronze

Re: 10k drives versus 15k drives: rotational speed issues

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Yes. For the smaller VNXs there are two different DPEs (2 SPs and 15 * 3.5" drives or 2 SPs and 25 * 2.5" drives) and for all the VNXs there are two DAEs (15 * 3.5" drives or 25 * 2.5" drives).

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jps00
3 Zinc

Re: 10k drives versus 15k drives: rotational speed issues

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The 2.5" drives have the same IOPs as a 3.5" drive, but slightly less average bandwidth for the same speed.  The lower bandwidth is due to the geometry of the smaller platter and the linear access of mechanical hard drives.

Actually, because of the VNX's SAS backend, you will need completely new DAEs for VNX.  Despite having the same name, they are differernt beasts.  That is, unlike the last several generations of CLARiiON where you could 're-purpose' DAEs from the previous generation, you must buy new.

The new DAE's for the 5000/7000-series VNXs are as follows:

15 drive (3.5" FF) 3U 6G SAS DAE will show as DAE6S in Unisphere

25 drive (2.5" FF) 2U 6G SAS DAE will show as DAE5S in Unisphere

RRR, I expect that you and Dynamox both have 7500s on-order?