Is there some way to pass along a safe shutdown in case of power loss? HP has told me there is no integration with a UPS and this seems odd to me.
I am glad I found this site it has already been great help!
7200 UPS
Re: 7200 UPS
They are correct, there is no ups integration.
That being said, there really isn't a need for one, and you truthfully don't want one
I think we can all agree that the issue with sudden power loss is half written data. That being said, if you have a ups integration with your hosts, then your ups will issue a graceful shutdown to your servers. They will then quiesce their memory and shutdown. This will stop all io to the array, which will then in short order flush its write cache to disk. So by the time power disappears, the hosts will be off, and the array will be consistent and silent in terms of activity, and so the shutdown will be safe, if not graceful.
If you did have a ups integration, you would have to be very careful that your hosts were offline before the array shuts down, lest the hosts have their storage disappear from under them, which is far more likely to cause corruption to your data.
Make sense? Or am I crazy/stupid/missing something?
Edit: fixed my grammar...
That being said, there really isn't a need for one, and you truthfully don't want one
I think we can all agree that the issue with sudden power loss is half written data. That being said, if you have a ups integration with your hosts, then your ups will issue a graceful shutdown to your servers. They will then quiesce their memory and shutdown. This will stop all io to the array, which will then in short order flush its write cache to disk. So by the time power disappears, the hosts will be off, and the array will be consistent and silent in terms of activity, and so the shutdown will be safe, if not graceful.
If you did have a ups integration, you would have to be very careful that your hosts were offline before the array shuts down, lest the hosts have their storage disappear from under them, which is far more likely to cause corruption to your data.
Make sense? Or am I crazy/stupid/missing something?
Edit: fixed my grammar...
Re: 7200 UPS
I agree, you want to address the gracefull shutdown issue from the host point of view.
Let’s say that the power issue is isolated to the array, the cache battery will guarantee that outstanding IO to disks isn’t lost – from the host point of view this IO is already committed.
Let’s say that the power issue is isolated to the array, the cache battery will guarantee that outstanding IO to disks isn’t lost – from the host point of view this IO is already committed.
Re: 7200 UPS
Honestly at this scale, you don't want automatic integration. When you've got 2-3 servers and a managed UPS, it's great to see an automated shutdown.
But with a 7200, and the presumably high quality datacentre it should be put in, the risk should be higher of running more issues with a problematic automated shutdown process, than with an unclean shutdown.
If you cleanly shutdown a SAN, and one server is still on its way shutting down, you'll just caused a major incident for that server. If something goes wrong with your software and the power's fine but the shutdown gets sent, you're down.
What if the UPS fails, but switches onto automated bypass which provides perfectly good power? I've seen this happen more than once - you don't want that to trigger an automated shutdown.
What if on power rail fails but the other is fine? Same scenario.
But with a 7200, and the presumably high quality datacentre it should be put in, the risk should be higher of running more issues with a problematic automated shutdown process, than with an unclean shutdown.
If you cleanly shutdown a SAN, and one server is still on its way shutting down, you'll just caused a major incident for that server. If something goes wrong with your software and the power's fine but the shutdown gets sent, you're down.
What if the UPS fails, but switches onto automated bypass which provides perfectly good power? I've seen this happen more than once - you don't want that to trigger an automated shutdown.
What if on power rail fails but the other is fine? Same scenario.
Re: 7200 UPS
Josh26 wrote:Honestly at this scale, you don't want automatic integration. When you've got 2-3 servers and a managed UPS, it's great to see an automated shutdown.
But with a 7200, and the presumably high quality datacentre it should be put in, the risk should be higher of running more issues with a problematic automated shutdown process, than with an unclean shutdown.
If you cleanly shutdown a SAN, and one server is still on its way shutting down, you'll just caused a major incident for that server. If something goes wrong with your software and the power's fine but the shutdown gets sent, you're down.
What if the UPS fails, but switches onto automated bypass which provides perfectly good power? I've seen this happen more than once - you don't want that to trigger an automated shutdown.
What if on power rail fails but the other is fine? Same scenario.
Good points. Just go ahead, buy a diesel generator (they are surprisingly inexpensive), and forget about graceful shutdown
It has been a long time since I configured UPS shutdown routines but now that I think about it, I never had a serious corruption issue due to power failure but I did had some unwanted shutdowns due to false alarms etc. Better live without it.