In my anecdotal, (not technical) experience, here are the issues with RAID5 failing (from losing 4TBs of Data and 2TBs of backups)
- Consumer devices - The later Buffalo terastations (Consumer NAS) and other 'low' price devices for some stupid reason tied the RAID array to their own hardware (like firmware) if the unit fails, the array fails.
- The size and 'time' to rebuild places a great stress on disks, therefore causing a potential 2nd drive loss. Rebuilding HDs for 250GB-500GB took a 90 min or so, a 2TB rebuilt takes several hours, all HDs are grinding to recover data at the same time, for hours as well, and this is when you are likely to lose more than the 1 drive and your array.
- Consumer and SMB NAS devices tend to buy the hard drives from the same manufacturer, at the same time, so when one drive fails, the other drives are just as likely to fail in the same time period. I lost two 1TB backups when the HDs had a 'suicide pact' and when I opened the Hard drives, I saw they were literally made the same day. To be extra paranoid, I used to have 2 or 3 different brand of HDs when I had my NAS.
- I recommend Synology units and constantly monitor the health of your hard drives. Totally agreed that RAID1 should be the golden standard. I've used several brands and Synology was rock solid.
- Consumer devices - The later Buffalo terastations (Consumer NAS) and other 'low' price devices for some stupid reason tied the RAID array to their own hardware (like firmware) if the unit fails, the array fails.
- The size and 'time' to rebuild places a great stress on disks, therefore causing a potential 2nd drive loss. Rebuilding HDs for 250GB-500GB took a 90 min or so, a 2TB rebuilt takes several hours, all HDs are grinding to recover data at the same time, for hours as well, and this is when you are likely to lose more than the 1 drive and your array.
- Consumer and SMB NAS devices tend to buy the hard drives from the same manufacturer, at the same time, so when one drive fails, the other drives are just as likely to fail in the same time period. I lost two 1TB backups when the HDs had a 'suicide pact' and when I opened the Hard drives, I saw they were literally made the same day. To be extra paranoid, I used to have 2 or 3 different brand of HDs when I had my NAS. - I recommend Synology units and constantly monitor the health of your hard drives. Totally agreed that RAID1 should be the golden standard. I've used several brands and Synology was rock solid.