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Adaptec Raid 5085 with no battery (on the raid card)

6 MSA60s

Raid 10

Big APC UPS with low load

Our building power needs to go out for 5 hours. Is it okay to shut down the raid for that long? One of our backup servers does not have a battery on the 5085 controller.

Just in case, I am backing up everything to tape.

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If you're anywhere between Chicago and the Atlantic Ocean, count on it being much more than five hours. –  Michael Hampton Oct 30 '12 at 3:12
    
Oh, and where are your UPS units and generators? –  Michael Hampton Oct 30 '12 at 3:18
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Why do you think it wouldn't be okay? It may help to understand your concerns/apprehension first. –  ewwhite Oct 30 '12 at 3:23
    
We have UPS units, but they will not hold the servers for more that 30 minutes. It will be a clean shut down. I just want to make sure the servers RAID volumes will be fine with NO power going to it for 5 hours.. –  InfoTech Oct 30 '12 at 3:39
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@InfoTech - ok, I think you're confusing some concepts here. The batteries in battery-backed RAID cards you hear about are there to protect the write cache in the event of a hard shutdown. It persists any writes there until power is restored, at which point they're flushed to disk. In your case, you'll be doing a clean shutdown, so this isn't an issue. Additionally, the RAID card config is stored in NVRAM as well as in several places on its member disks. So not to worry, you're all good. –  EEAA Oct 30 '12 at 4:02
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2 Answers

up vote 5 down vote accepted

Yes. Backup battery is required to survive unclean shutdowns (i.e. yanking the power cord out).

A clean shutdown and you can have it offline for days, weeks, months or even years. OK maybe not years as the battery probably won't work when you get back, but you get the idea.

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"Additionally, RAID10 does not require a battery-backed cache as it does not have the write-hole that RAID5 has." The what?! The battery is for the cache... like things that are by definition, not on the disk yet. It doesn't matter if it's parity or whatnot. –  Chris S Oct 30 '12 at 3:38
    
I don't have a battery on the 5085 Raid card. Is that an issue? It will be removed completely from power for 5 hours. Clean shut down.. –  InfoTech Oct 30 '12 at 3:41
    
Clean shutdown & no battery = Good forever (± a few decades) –  Chris S Oct 30 '12 at 3:42
    
@ChrisS - I have never seen a RAID10 card that requires a BBU, as writes are flushed immediately. RAID5 has parity to calculate, and thus it reports it as flushed when it isn't, otherwise write performance is abysmal. Some RAID controllers won't even let you enable RAID5/6 without a BBU, but they will let you into RAID1/0/10 without issue. –  Mark Henderson Oct 30 '12 at 4:08
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Just shut the server(s) down first... The RAID enclosures will be fine. It is okay to shut the RAID system down. Your only concern needs to be that you don't have any writes in transit.

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Clean shut down. My only concern is that there will be NO power for 5 hours, at all & the 5085 raid card does not have a battery pack on it. When I reconnect power, will my raid volumes come back up? –  InfoTech Oct 30 '12 at 3:43
    
@InfoTech Have you really not turned your servers off before? It should be fine. –  Zoredache Oct 30 '12 at 6:45
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