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Hi,

Was going to ask a tech question and then just discovered another hard disk issue so am trying for a two-fer here.

1. I just realized I lost one of my VI drives, an HD with two partitions. One of the partitions still mounts on the Desktop, but the other does not. I was able to perform Disk Repair on the partition, but it still doesn't mount. It looks like the disk is completely full. I probably accidentally downloaded a couple big VIs onto it by mistake, as I usually try to keep around 100g free. Do I need to erase the disk completely to use it again, or is there any way to surgically erase enough material to get it to mount again?

2. I installed a new SSD in my old 2011 iMac a little more than a year ago. I had a tech do it and he installed High Sierra. My old HD is still active and available, and still on Sierra. I've griped a bit over the past year that with DP 9.52 and High Sierra, some power hungry VIs cause a performance spike and audio glitches, while with 9.02 the performance may spike but the audio doesn't glitch. Out of curiosity I booted up in Sierra on the HD, and discovered that a particularly troublesome preset didn't glitch in 9.52 under Sierra. Yay! I suppose I could go back to my HD, but the speed with the SSD is just too much to give up.

So.... I wondered if it would be possible to install Sierra on the High Sierra SSD. Would there be an issue with the new file saving format in HS? I have a couple Sierra install zips that could be used, but wanted to make sure first if this was possible or advisable. I've gotten along with High Sierra for the most part, and concerned about security issues going forward with Sierra, but not having the audio glitches would be huge at this point .

Anyway thanks for any help!!

2. It is likely that something else is going on and the problem is not what you think it is. It could be the HHD as SSDs will throttle down if they get too hot and you have a heat pump in there that will burn your fingertips if you touch it. High Sierra cannot cause “power hungry” plugs or VIs to crash your iMac but other things can.

Your tech did you no favors by leaving the original HDD inside. These run extremely hot and cook an iMac from the inside. I have never pulled one that was still good after 4 years. It might pass Disk Utiity SMART but a more coomprehensive test like the one in TechTool Pro? I’ve posted typical screen shots before.

GPU problems are common on these. Generally, they are fixed by baking the unit which reflows the solder. Again, the real culprit is the HDD. It causes the GPU to vary widely in temperature causing the solder joints to crack over time.

The reason it was left in was to save you a few $$ on the OWC temp sensor that you need when the spinners are removed. $40 from OWC.

With 2TB SATA III SSDs now costing less than $300, it makes no sense not to put one in.

1. Mechanical hard drives need at least 10–12% free space or performance slows to a crawl. There is no reason to partition a VI drive and hasn’t been since SATA was introduced with the G5. Since a 2011 iMac has USB 2, an SSD over Thunderbolt will give you decent performance or you can mount an SSD inside. A 2011 27” iMac has two SATA III busses and an SATA II buss for the SuperDrive.

Thanks Mike, as always, hoped you'd find the thread!

Following up:

2. Thanks for the info on HDDs cooking. I actually very rarely boot up in the HDD and don't use it for documents etc. so hopefully that keeps the cooking down, though I have noticed that sometimes the iMac can get very hot. I did notice that one of my hungry VIs played without glitching in 9.52 on the HDD boot under Sierra, but had glitching on the same patch 9.52 on the High Sierra SSD, hence my thinking that perhaps the interaction between DP and Core Audio in HS was causing problems. Replacing the HDD with a 2T SSD is certainly intriguing (I assume that having the 2 SSDs in the 2011 iMac would reduce the heat factor?), but since the mid 2011 iMac can't be upgraded to Mojave or beyond, I've resigned myself to the fact that I may have to buy a new machine sometime in the semi-near future anyway.

Regarding:

1. At least the mountable partition 2 of my external HDD shows me that the entire drive isn't dead, but it's looking like I'll have to erase partition 1 to get it active again. I'll probably lose some things but I had already transitioned many of my VIs to a 2T SSD, and Kontakt is telling me which VIs I'll have to reload, most of which I have on one backup drive or another. A hassle to be sure, but that drive was getting to be a bit of a mess anyway. Do wish I could surgically delete something to make room, but again there doesn't seem to be any room on the disk and it will not mount.

Thanks again!

Steve