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Storage system power saving
I really like the option to be able to spin down the spindels that are unused to save power on the Clariion system but wanted to see what the caveat would be.
I guess my question is why would someone not enable this option?
Thanks.
christopher_ime
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February 5th, 2011 15:00
We have a short whitepaper "White Paper: An Introduction to EMC CLARiiON CX4 Disk-Drive Spin Down Technology — Applied Technology" that could influence your decision, and if you do choose to enable it discusses how to manage it, explanation of the algorithm that decides what defines is "idle", best practices, etc:
From PowerLink, the breadcrumb trail is as follows:
Home > Support > Technical Documentation and Advisories > Hardware/Platforms Documentation > CLARiiON CX4 Series Systems > CLARiiON CX4-120 > White Papers
In summary, the main considerations with spin-down are:
1) Reliability due to spin-up/spin-down cycles
There is a section: "Reliability" which discusses the testing EMC performed, and also the proactive measures that are performed by Navisphere/Unisphere to verify that a drive will, in fact, spin-up as noted in the "Ongoing processes that ensure reliability" section.
2) Inherent latency as the drive needs to first spin-up before being written from/to
As noted, backup and archiving is a work-load profile that is a "natural fit"; for other applications keep this in mind. There is, of course, compromises (power savings vs. latency).
3) Also, FLARE limits the number of drives that can spin-up simultaneously in the same enclosure (DAE) thus adding to the overall possible latency:
a) Up to four at the same time
b) Waits 12 seconds before spinning up the next set of disks
Finally note there are restrictions enforced by Navisphere/Unisphere (cannot use with layered applications and cannot be enabled on the first five system drives):
tkjoffs
159 Posts
1
February 6th, 2011 19:00
We do not enable this because of the latency that it causes in regard to performance. In "most" environments I have come across, SAN is used for OLTP/DB and ESX systems which are typically in high use during the day and maintenance use during the night for backups, etc. I just don't see the benefit for this unless you are running a well configured tiered storage system where you archive data off to a certain set of spindles, in which case spinning down the archive data spindles might not be a bad idea.