[dirtdevil]

I want to setup a SAN server using a mix of different speed drives and have multiple arrays. So I would have a raid 1 of 2 7200RPM drives and a raid 1 of 2 10K RPM drives. I heard that having a mix of different drive speeds in the same physical box can break arrays because the vibration caused by the different drive speeds screw up the read/write heads in the drives. Is that true? I also heard that if it is true that you can do that as long as the chassis specifically supports the use of different drive speeds in it.

[continuum]

That sounds like a load of crap.

Chassis makers and SAN vendors do see drive vibration as a major concern, but "mixing drive speeds" is a very poor way to word that as an issue. I'm not aware of a single vendor who explicitly tests for a mix "different drive speeds" in it.

That said, vibration in these devices is a serious concern; using nearline or enterprise disks designed for such use (Seagate Constellation, Seagate Cheetah, Seagate Savvio, Hitachi Ultrastar, Western Digital RE, etc.) is strongly recommended.

[dirtdevil]

I'm using a new dell server with seagate drives. So as long as I stick with the enterprise level drives, I should be fine? I've also heard it's bad practice in general to mix different drive speeds in a single enclosure regardless of the whole vibration thing. But I can't understand how that would be true since there are plenty of high end enclosures that support 30+ drives. With all the speed and size requirements for data, I find it hard to believe they would build such an enclosure to only use one drive speed.

[continuum]

They don't "build" an enclosure to use only one drive speed, but they may only test with a single type drive rather than mixed drives (since that vastly complicates the amount of testing they'd have to do!).

As far as it being a Dell server, I don't know if Dell firmware-locks their controllers so that you can only use Dell-sourced drives, or if 3rd party drives are ok.

[Kevin OBrien]

continuum, on 10 November 2011 - 09:14 PM, said:

That sounds like a load of crap.

Chassis makers and SAN vendors do see drive vibration as a major concern, but "mixing drive speeds" is a very poor way to word that as an issue. I'm not aware of a single vendor who explicitly tests for a mix "different drive speeds" in it.

That said, vibration in these devices is a serious concern; using nearline or enterprise disks designed for such use (Seagate Constellation, Seagate Cheetah, Seagate Savvio, Hitachi Ultrastar, Western Digital RE, etc.) is strongly recommended.

Call it being bored late at night stumbling into old threads that remind me of old review content, but I recall Hitachi brought up the vibration tolerability levels of their enterprise hard drives. It was less and argument about having mixed rotational speeds and more on having say 8-16 drives in the same chassis all with a random workload. You have unique vibrations coming from the heads seeking on each drive which impacts everything. Hitachi released a paper on it covering their technology called "Enhanced Rotational Vibration Safeguard" which used g-sensors to detect the vibration and adapt on the fly.

http://www.hitachigs...RVS_25March.pdf

So yes vibration is a problem, but more for arm actuations and less for different rotational speeds.

[continuum]

Yes, drive interaction in large arrays is well documented.

Note that it doesn't specifically address different rotational speeds, it's just that they don't test for it-- there's enough permutations of drives to test already, so no one generally expands their testing to deal with it.

And since nearline disks have RVS or RAFF (or whatever they choose to call their additional G-sensors and firmware optimizations), well, it helps. We spend enough money on testing here on our production configurations, testing non-production configurations is far beyond the scope of what we can afford to do.

[kittle]

What continuum said..

Also as an FYI, ive had a mix of 7200rpm and 10krpm drives running for over 5 years in my server with zero problems. Server is on almost 24x7, but theres only 5 drives total.

[nova28]

Have been running my server with mixed drives for 5 years now. since 2 years it consists of 6x1TB R5 + 6x2TB R5 chains on a Areca 1260 card. Never had a drive fail on me. Using desktop class drives in aSharkoon Rebel 12 Economy-Editon chassi. that I bought from Caseking.de back in 2008. Runs 24/7

This post has been edited by nova28: 01 March 2012 - 04:53 PM