DASD storage levels

435 pts.
Tags:
DASD
Storage
Is there a recommended storage level percentage for optimum performance / cost ? Obviously I realise there are lots of factors to take into consideration, such as projected growth, disk sizes / arms, I/O etc. But with all these catered for should I be looking at something around 75% or say 50%? 50% would seem low to me and that I will have a lot of moneys’ worth of Disk sitting round doing nothing, 90% would seem high with little room to react if there were issues. I am trying to identify a band say 70 - 85% where the ideal level of utilisation should sit so I can convince my users there is no issue with us being at 85% but also to convince my purse holders that we need to by more when we start getting towards 90%. Taking into consideration the system husbandry is maintained. It’s not just about cost and forward planning but also about convincing them that seeing disk at 85% is not going to cause any issues in performance, given that the page faults are within the tolerances recommended by IBM. I know it’s a vague question but you guys have a vast of experience and I am asking for your views or IBMs if indeed they have one.

Software/Hardware used:
V5R4, V6R1, Power 5's, 6's and 7's

Answer Wiki

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First thing to do is find out what is take up space on the disk. The more we have, the more we collect data. Sometimes a good cleanup can reduce disk utilization by 10 to 30%.

Next you need to set policies on file retention.

Now that your system is clean, if you are at 80%, you should have ordered  more disk and be waiting to put it in.

If you are running below 70% you should be OK. 

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  • TomLiotta
    ...with all these catered for should I be looking at something around 75% or say 50%?   With "all those catered for", I have no problem thinking of 50%-75% as a good healthy range. Whether it should be closer to 50% or 75% will depend on the metrics for "all those" and a couple others.   I've worked with systems that had no problems at 95+%. But I have no idea what your values are for "optimum performance / cost". Nor do I have any idea what performance tuning has been done on your systems, nor what your workload profiles are, nor the volitility of your database, nor the prevailing access methods, nor any factors such as journaling/commitment control, nor...   Given what's known, I don't think there's any good way to get closer than a guess of "50%-75%" for "optimum performance / cost". It's as good a guess as any.   Tom
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  • jinteik
    one of the ways is to like draft a chart on how fast the DASD is taken then from there you can kinda guess how much u need. last time i too work with a system with about 90-95% but it work fine, but like Tom say it depends on the values that you have set. to me 50-75% is also a healthy range.
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  • Guy553
    Thanks for the answers guys; I'll close this topic now. I do have systems running at 90% and I also have system running at 50%. One observation I have made is that the higher the % the more clean up both Apps and Infra do! Yes it is driven from necessity but still carried out more frequently, I find it very difficult to get my apps guys to archive or clean up when we are closer to 50% even after providing them with reports naming and shaming.
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