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Old August 6th 20, 01:28 AM posted to comp.sys.ibm.pc.hardware.storage
Mark Perkins
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Posts: 110
Default "Western Digital releases new 18TB, 20TB EAMR drives"

On Wed, 5 Aug 2020 18:49:03 -0400, Yousuf Khan
wrote:

On 8/4/2020 11:21 AM, Mark Perkins wrote:
On Tue, 4 Aug 2020 03:25:25 -0400, Yousuf Khan
wrote:
That's exactly the point! Modern HDD designs are taking away their
random access features and replacing them with serial-access features.


That's crazy. Why would you say that?


What do you think SMR is? SMR requires a serial write pattern to
optimize its writing performance. If you try to write to an SMR drive in
a completely random way then performance drops 10x. HDD's are thus
becoming more serialized devices.


Wow, you're seriously confused. SMR is *NOT* a serial write pattern.
Whoever told you that is wrong. It doesn't even make sense.

Hard drives can reliably read data in much narrower tracks than they can
write it, so disk capacity has traditionally been limited by how tightly
the tracks can be packed together without losing the capability to write a
single track. SMR simply groups the tracks into sets of 'zones'. When a
track needs to be written, the entire zone that the track belongs to is
written. During reads, individual tracks can be read exactly the same as
with non-SMR drives.

So, no serial writing or reading. The downside of SMR, and the reason why
the technology has a bad name, is that once data has been written to the
drive and now it's time to update a track, the zone (group of tracks) will
have to be read first, before the zone can be (re)written. That slows down
the writes compared to non-SMR, but reads are unaffected since individual
tracks can be read without any issues or special tricks.