kjstech
3 Argentium

need to enable write cache when SPS is faulted

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I know why write cache is disabled when an SPS is faulted, but I need to enable it anyway.  The whole room is on a new UPS that was recently tested, I'll take my chances.

We are seeing latency in vmware from 300 to 13,000 ms on various datastores housed on an NX4 Celerra.  This is causing a massive service failure for our business and I've tried to escalate the ticket we have with EMC numerous times.  However we are in the dark as to when a tech will arrive with a replacement SPS.  So in the meantime I want to force enable the cache, or somehow make the system "think" the SPS is not faulted so that it will enable the cache.

Any secret non-published command anyone know of I can plug in to enable write cache again?

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AnkitMehta
4 Germanium

Re: need to enable write cache when SPS is faulted

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Without a working SPS battery, you cannot enable Write cache - no secret commands.

Check with your ASM/DSM about EMC CE visit, if it getting delayed, they should be able to help you out with alternatives.

kjstech
3 Argentium

Re: need to enable write cache when SPS is faulted

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Thanks Ankit,  I was afraid of that.

I've reached out to area service manager so hopefully we can get this resolved soon.

My highest latency in vmware is 80242 ms read latency and 58044 ms write latency.  Though the latest highest is 14411 ms write latency.

I had to modify employees Outlook to go to cached mode instead of read directly from Exchange server.  Also had to power off a lot of non-essential VM's. 

It's amazing what write cache does for the performance on these things.  When that SPS was fine, everything ran smoothly.  It's like night and day... hence my plea to see if there was any way to enable write cache... even if undocumented / diagnostic code or some kind of "force-able" command.

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AnkitMehta
4 Germanium

Re: need to enable write cache when SPS is faulted

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I'm afraid there is none.

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kjstech
3 Argentium

Re: need to enable write cache when SPS is faulted

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When it arrives and is installed, how long do you think until it is fully charged and write cache can be enabled?

My understanding the SPS holds the disks up long enough just to flush the current cache to disk, so that isn't a long amount of time... maybe 10 to 30 seconds.... that little bit of time shouldn't take too long to fully charge, right?

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kjstech
3 Argentium

Re: need to enable write cache when SPS is faulted

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Well the SPS is replaced now and it took about 10 minutes for the new one to charge.  Now our performance is back.  Thanks for your help.

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kelleg
5 Rhenium

Re: need to enable write cache when SPS is faulted

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glen

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