by OLIMEX Ltd in ARM, linux Tags: arm, hdd, linux, low, Power, sata, server

We have server rack with several x86 servers running Linux with our work file repositories, the ERP and etc.

They are quite power hungry as lot of HDDs are connected to them in RAID mirrors to prevent data loss.

We are located in industrial area and power supply glitches are not uncommon, specially during the winter.

To keep the servers alive during power downs, we had to buy expensive 2000 EUR UPS, which actually keep them no more than 20-30 minutes up when power is down, so basically just to allow you 10-15 minutes to finish your work and then to shut them down properly before the battery is drained.

This UPS has lead-acid batteries inside which has to be changed every 3 years and cost almost as much as the UPS itself.

Initially we kept our all Olinuxino Linux images on Gdrive, but there were few issues with this, the images grew to many Gigabytes, and Gdrive start to restrict the access to the files after some limits were reach, so we decided to host these images by us on torrent. We decided to make separate server for this due to security reasons, we just wanted to keep our local network private and to allow external access only to this isolated server which we access also from outside like other users.

To keep it as low power as possible we setup one A20-LIME + HDD320GB + 6600mAh LiPo battery. This configuration works well several years already.

Yesterday our power supply provider EVN warned us that they will change mains high voltage cables in our area and Olimex will have power supply cut from 9.00 to 15.00, so we had to take day off.

We came today and sure we found all x86 servers down, but to our surprise the LIME with the HDD was working fine all these 6 hours of power blackout and didn’t shut down!

We know that with 6600mAh battery the LIME will last at least 10 hours as it uses 1.5-2W, but the HDD is rated 5W (5V/1A), so we were expecting less time stand alone operation.

It was good surprise to see that actual consumption is less, maybe the HDD enters stand-by mode when not used?