18TB HSMR hard drive - READYNas

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Yoda3647 wrote:

but I purchase one to replace one of mine that failed, found it on Facebook brand new unopened $100 for a 18TB HSMR. I have all ready put it in my NAS and it seems to be working. Would it be okay or should I start looking for a replacement? When I talking to the guy I mentioned I might want more and he said if I purchased 5 he would sale them to me for $80 per 18TB drive.    

 

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I'm not seeing any info on this drive on Western Digital's website - the closest thing I see is the HC650, which is a host-managed SMR SAS drive (which won't work at all in a ReadyNAS). I suspect the drive you purchased isn't generally available to the public (if it was, the WDC website would list them). I have no idea on how well it will work (and is why I said I'd personally avoid HSMR).  

The challenge with SMR technology is that sustained write speeds can be extremely slow.  When you write to track X, the contents on track X+1 are also overwritten.  So when doing a write to track X, track X+1 needs to be read first.  After track X is written, track X+1 needs to be re-written.,so track X+2 needs to be read before that can be done.  This "rippling" process continues until you reach the end of a zone - there is some extra space between zones, so the last track in the zone can be written without overwriting the data in the first track of the next zone.  

"Host managed" SMR means that the server (in this case the NAS) needs to explicitly manage this write process in the device driver.  ReadyNAS don't have a driver that will do that. 

A "Disk Managed" SMR disk manages the writes itself in the disk firmware - generally with the help of a large cache, to minimize performance impact.  Still, sustained writes will eventually overwhelm the cache, and when that happens the transfer speed drops to a crawl. So disk-managed SMR disks kind of work, but not well - some folks here have tried them with rather poor results - and some actually ended up losing their volume.

Without documentation, there's no easy way to tell if this is host-managed or not.  Since it appears to work, it could be disk-managed.  Or maybe the out-of-the box setup for this disk is pure CMR, with SMR being configured manually if you want that.  Or maybe you just haven't tried to access data written to the SMR portion of the hybrid drive.