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Need to find a way to force array utilization lower
I've run into problems where the pre-flight check will not pass due to high array utilization. This is an array shared by many disparate resources, most of which I have no control over. It is in need of a FLARE upgrade to resolve some annoying bugs and I'm looking for any recommendations on how to force utilization lower.
One thought was to use NQM, create an IO policy and knock ALL LUNS to under a given total number of IOs.
TIA
James
One thought was to use NQM, create an IO policy and knock ALL LUNS to under a given total number of IOs.
TIA
James
calle2
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July 15th, 2008 13:00
I assume that you are using NST... It is "only" bothered about the IO on the FLARE spindles. In most cases a single RAID-5 RG covers the first five (5) spindles. Hence you need to drive down the IO on the LUNs on those spindles...
Obviously you will want to do your upgrade during a quiet period anyway.
I hope this helps
Carl
ovivier
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July 16th, 2008 00:00
ovivier
142 Posts
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July 16th, 2008 01:00
So I am going to migrate luns But leaving 5 disks empty is quite expensive ! I think I will re-use them after the upgrade.
My NDU is from 22 to 26.
RRR
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July 16th, 2008 01:00
Furthermore: if you upgrade from F19 to 26, you need more free space on the Vault drives since F26 needs more space....
What we do nowadays is to install a Clariion with the smallest drives possible in the first 5 positions and then leave them empty for any future Flare upgrades.
RRR
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July 16th, 2008 02:00
But if you need to empty them for extra space, I'm not sure of since F22 / 26 don't differ (much) I think. Better ask your CE if extra space is needed if you go from 22 to 26.
AranH1
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July 17th, 2008 08:00
I don't think that is the only checks it performs. Remember that during a FLARE upgrade the SPs will reboot one at a time so the CPU utilization on each SP needs to be below 50% to ensure that one SP can host all the i/o and disks during a reboot of the peer SP.
Aran
calle2
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July 18th, 2008 04:00
OK very valid point! The checks are obviously there for valid reasons. I should have formulated my answer more carefully as the original question was to find ways to force array utilization lower.
I shall stand corrected
Carl
AranH1
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July 18th, 2008 08:00
But yes the question itself is a tough one. Without some cooperation from the administrators of the applications hosted on the array it will be difficult to minimize the utilization of the array.
James,
Do you not have a maintenance schedule for systems in your infrastructure? A FLARE upgrade while usually non-disruptive does have the potential to impact not only i/o but there is the possibility of an actual outage if something goes wrong.
FLARE upgrades should be done during low i/o periods after full backups of all the systems on the array. Because the SPs reboot during the upgrade write caching will be disabled for most of the upgrade process which will seriously impact the performance of the array.
Aran
DGM3
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July 23rd, 2008 21:00
more free space on the Vault drives since F26 needs
more space....
R26 does not require more reserved space than R19.
There are differences in reserved space size, but it is platform dependent (depends on array type), not FLARE revision specific.
For example; a CX700 will require/use the same amount of reserved space, independent of whether it is running R16, R19, R24, or R26.
A CX3-series array requires/uses a larger reserved space - this is true independent of whether it is running R22, R24, or R26.
Regards,
DGM
RRR
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July 24th, 2008 01:00
DGM3
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July 24th, 2008 11:00
Regards,
DGM
jhoward5
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July 25th, 2008 04:00
We are very much aware of the possibility of something going wrong and the performance impacts of cache disable during reboots, customers seem to tolerate that pretty well.
I may resort to rate limiting I/O in the fabric to the array in question not that I want to do that
J
AranH1
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July 25th, 2008 07:00
Have you looked at Analyzer to see if there is any time during the day/week that the array is at a lower level of utilization?
driskollt1
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December 16th, 2009 12:00
NQM Is pretty nice but still needs some work IMO.
It's hard to manage multiple things at one. If you've got a few problem areas, then it's pretty good. I think it would be a pain to configure for your whole array.
I got NQM to manage some of our new Sun servers. They push writes too fast (super fast servers) and fill up cache to 99% with anything fewer than like 60 spindles (RAID10) for a LUN. NQM let me limit the IO of those LUNs so that the disks could keep up.