Don’t Be Afraid of RAID
I&#x27;ve read through the article and it turns out to me that he wrote it to show he was lucky enough not to experience a multi-disk RAID failure. Personally I owned dozens of HDDs across almost all brands from desktop&#x2F;laptop HDDS to Enterprise HDDs or NAS HDDs and almost half of them had bad sectors with a life span of a couple of months to a few years, some of which even broke in a row in a few days. The only exception is that in my last batch of 5 Seagate NAS drives, there was no single failure after around 4 years and I think I&#x27;m just been lucky with those as I did hear quite a few people were complaining about the same model.<p>Due to the nature of how HDD works, the surfaces of the disks have more or less defects leaving the factory and were graded by the count of defects, and even the enterprise grade one are not free of defects. Those defects and adjacent areas then are masked by the firmware so that magnetic heads won&#x27;t trying to read&#x2F;write to&#x2F;from them. But that won&#x27;t prevent them from growing. The factories are very clean but the dusts in the air are simply impossible to avoid and if one lands on the disk, it&#x27;s a time bomb. Also as the disks&#x27; capacity grows, the tracks get narrower and narrower. The disks spins from 5400 rpm to 15000 rpm maybe even faster and the magnetic heads are gliding micros from the disk and if the heads touch the disk surface, it almost for sure to create a bad sector event bad tracks. And again, the vibrations are impossible to avoid. Making it even worse, the contact are almost guaranteed to generate debris to be scattered to the whole disk, event goes to other disks sealed in the same case. The bigger capacity, the narrower the track will be, the less tolerant to such contact. Based on the fact, I really don&#x27;t see where he got the confidence the disks people bought were not going to have bad sectors during their expected life span.<p>Also the disks people use to build the RAID are most likely the same brand, the same model and the same batch and thus if one started to have bad sectors, most likely the others are going to have them soon or even worse may already have them. Even if the other disks in the array do not have bad sectors at the time of the failure, they are highly likely going to have during the rebuilding process, why? The load. Take a 10TB drive as an example, my Seagate 10 NAS drive can deliver ~180MB&#x2F;s peak writing and ~80MB&#x2F;s at the trough. Let&#x27;s assume it can deliver 100MB&#x2F;s all the way, and the disk is half full it will almost take 14 hours to finish, this load is highly likely to push other drives to the limit. For RAID6 allows another 1 to fail. For RAID5, if another drive failed during rebuilding, you data is gone. If you had to rebuild a 12 bays NAS, you would know how frustrating it could be, especially when there were secondary failures.<p>Software RAID may somehow alleviate the problem a little bit but it will also cover up the issue. My experience was that once there is one single bad sector, there will be lots of them soon, if you don&#x27;t back up the data and replace the faulty drive on spot, most likely it will be too late.<p>All above does not event consider the setup and quirks of NAS or RAID cards. Put all those issue aside, what&#x27;s are the benefits of RAID for home users? IMO, almost NIL. Our home network device most likely are Gigabyte ones with 1 Gbps ports, which can only deliver about 100MB&#x2F;s, you can see that a single drive can almost saturate that bandwidth even with link aggregation. And most people does not need the random IO boost or extra large volumes come with RAID.<p>My suggestion for home users is to go single drive and stay away from RAID.