eSATA HD randomly disconnects/disappears

I have 2 Western Digital external hard drives. 500GB each. One is hooked up through USB2 and the other uses eSATA. I'm running Vista 64bit Ultimate and my mobo is an Asus A8N32-Sli.

My problem is that the eSATA HD randomly (it seems) disconnects or disappears from My Computer after a while (anywhere from 1hour to over 24 hours) of being plugged in. If I unplug and replug it in it is recognized and works fine. If I use USB2 there are no problems.

I have power management set to never turn off the HDDs and I have a brand new cable on it. I haven't cut or trimmed it yet as I want to make sure there isn't something else I'm missing.

Why is it doing this and how can I fix it? Thanks for your time and advice.

Ok, I bought two new HDDs and they still have the same problem. When connected via eSATA they randomly disconnect themselves. I have to power off and then on again and then they work fine again for some random period of time.

I get 3 different event messages in the event viewer when this happens.

First I get a, "The device, \Device\Scsi\SI31321, did not respond within the timeout period."

Then I get, "The device 'WD My Bo ok SCSI Disk Device' (SCSI\Disk&Ven_WD_My_Bo&Prod_ok&Rev_01.0\5&193467b2&0&000000) disappeared from the system without first being prepared for removal."

And at the same time I get, "The device, \Device\Harddisk1\DR1, is not ready for access yet."

Any further ideas on how or if this can be fixed? I'm beginning to think this is purely an ASUS mobo issue or an issue with the Si controller.

I am having the the exact same problem but with a Seagate 1TB Free Agent extreme. I'm running Windows XP Pro - 32 bit, Intel SE7525 GP2 of a on a PCI express card. Different HDD, MB, OS - same problem. I ran SeaTools DX but nothing came up. I don't have a clue as to what is going.

I'm having the same problem running Vista 64 Ultimate on a Shuttle Barebone with nforce 630 chipset and a Hitachi 1TB drive in generic eSATA/USB enclosure. It's maddening and I can't seem to find a solution.

The stupid enclosure I have my drive in unfortunately doesn't support spin down on inactivity via USB so that's not an option since the box is running 24/7 as a home server. Grrrr.

I was able to fix my problem of the external eSATA HD disconnecting. Using Vista HOme Premium SP2 in power options there is an advanced screen which has a menu similar to device manager. under 'hard disk' there is a 'turn off disk after'
option which was set to 20 min. I set it to never and have not had a problem since. It originally looked like the disconnect of the HD was random but I guess it was always 20 min after the last access. This migh not work for all problems listed here but it did fix it for me. good luck LArry