On Monday, 6 January 2020 13:53:41 GMT Rich Freeman wrote: > On Mon, Jan 6, 2020 at 8:25 AM Mick <michaelkintz...@gmail.com> wrote: > > If they are used as normal PC drives for regular writing > > of data, or with back up commands which use rsync, cp, etc. then the disk > > will fail much sooner than expected because of repeated multiple areas > > being deleted, before each smaller write. I recall reading about how > > short the life of SMR drives was shown to be when used in NAS devices - > > check google or youtube if you're interested in the specifics. > > Can you give a link - I'm not finding anything, and I'm a bit dubious > of this claim, because they still are just hard drives. These aren't > SSDs and hard drives should not have any kind of erasure limit.
This (random) link strongly recommends against usage in NAS, but gives no reliability data: https://www.storagereview.com/seagate_archive_hdd_review_8tb This is a youtube video where someone was comparing SMR failures on a NAS: https://www.youtube.com/watch?v=CR_bfbOTY1o > Now, an SMR used for random writes is going to be a REALLY busy drive, > so I could see the drive being subject to a lot more wear and tear. > I'm just not aware of any kind of serious study. And of course any > particular model of hard drive can have reliability issues (just look > up the various reliability studies). Right, I haven't seen any lab reliability studies published. I would think more information could be sourced in IRC/ML where datacenter sysadmins hide to compare their ... hardware. :-) Reading another random link it seems Dale's 8TB SMR drive has a 20GB conventional PMR platter/area in it to catch and cache any small writes. The firmware will subsequently transfer the cached data on the SMR area of the drive in due course, after it deletes the requisite adjacent overlapping tracks. This means up to 20GB of initial writes will be normal, dropping to lower speeds thereafter as the PMR cache needs to be flushed: https://www.ixsystems.com/community/threads/smr-hard-drives-do-you-think-they-are-proper-nas-drives.35805/ If this is so, it explains Dale's observation of a hyperactive disk, well after it was dismounted. Its firmware's been busy! [snip ...] > Granted, I don't rewrite it often but unless zfs is > SMR-aware it is still going to be writing lots of modest-sized files > as the original files get chunked up and distributed across the nodes. > On the disk lizardfs data just looks like a browser cache, with > everything in numbered files about 60MB in size in my case. The files > also appear to turn over a bit during rebalancing. I would think bit flipping between the 20GB PMR cache and the 8TB SMR tracks represents an increased risk, vis A vis a single-step data transfer. Data scrubbing well after the write has completed and committed to the SMR tracks would reveal any anomalies. What would seriously mess things up is creating a raid with mixed PMR and SMR disks and running big (bigger than the internal cache) data writes. Some PMR disks will complete well before the SMR. I/O blocking and timeouts could ensue and the applications performing the writing could hang/fail. Anyway, write once - read often, fits well the use case for these disks. They should be right at home for long term video and media storage. -- Regards, Mick
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