Very slow iMac after being unplugged accidentally

[AriKrook]

I accidentally unplugged my iMac while it was waking up from sleep. Since then it is dreadfully slow accessing the hard disk (Fusion drive). I formatted the hard drive and installed a new OS. even installing the OS (which should take 13 mins) takes an hour and a half. What could be wrong?

 

[MadDane]

Which model do you have? Both size, year and so on. It could be the hard drive that has been damaged by the power shortage, since you mention you have reformatted it. Have you tried doing a hardware test?

 

[AriKrook]

Which model do you have? Both size, year and so on. It could be the hard drive that has been damaged by the power shortage, since you mention you have reformatted it. Have you tried doing a hardware test?

Hi MadDane, Thanks for your reply. I found out what the problem was: the OWC SSD drive in my 3TB FusionDrive. I "disconnected" it from the HDD and noticed that the HDD acted normally and the SSD was extremely slow. Strange, because I could format it no problem and DiskUtility did not find any problems.
How do I do the hardware test you recommended?
By the way, my iMac is an early 2009 24" iMac running El Capitan. I upgraded it two years ago with a 3TB HDD and the 240 GB OWC SSD. It has been running beautifully (until yesterday).

 

[maflynn]

Did you run the Disk Utility to check for errors and see the SMART status?

Try running the AHT, to see if anything kicks out.

If I were a betting man, I'd say the hard drive is having issues

 

[MadDane]

Hi MadDane, Thanks for your reply. I found out what the problem was: the OWC SSD drive in my 3TB FusionDrive. I "disconnected" it from the HDD and noticed that the HDD acted normally and the SSD was extremely slow. Strange, because I could format it no problem and DiskUtility did not find any problems.
How do I do the hardware test you recommended?
By the way, my iMac is an early 2009 24" iMac running El Capitan. I upgraded it two years ago with a 3TB HDD and the 240 GB OWC SSD. It has been running beautifully (until yesterday).

I am glad you figured out what the issue is. You can run the Apple Hardware Test by holding down D when you start up the computer. There is a guide here how to do it: https://support.apple.com/en-ap/HT201257

 

[maflynn]

Hi MadDane, Thanks for your reply. I found out what the problem was: the OWC SSD drive in my 3TB FusionDrive.

Oops, my bad, looks like you posted this as I was posting mine. Glad to see that you figured it out

 

[AriKrook]

Did you run the Disk Utility to check for errors and see the SMART status?

Try running the AHT, to see if anything kicks out.

If I were a betting man, I'd say the hard drive is having issues

Hi maflynn, Thanks for replying. It appears to be the SSD. Installed OS on HDD and Mac runs fine.
Diskutility shows no problems for SSD. I cannot run AHT.
I try to copy a lot of data to the SSD. The first 2 GB seem to go OK (Time remaining: 4 hours), then write speed reduces to practically zero (Time remaining: 3 days).

Do you know of an alternative to AHT?

Thanks, Ari

 

[maflynn]

Do you know of an alternative to AHT?

DiskWarrior comes highly regarded.