Mailinglist Archive: opensuse (946 mails)

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Re: [opensuse] WD Green AV HD: rsync read errors mapping
  • From: Greg Freemyer <greg.freemyer@xxxxxxxxx>
  • Date: Fri, 8 Sep 2017 18:17:56 -0400
  • Message-id: <CAGpXXZKVC7cMx=1MMDrp=sW8gQZc1M0G6Kp8o4=_1RjRodRsVg@mail.gmail.com>
On Fri, Sep 8, 2017 at 5:57 PM, Carlos E. R.
<robin.listas@xxxxxxxxxxxxxx> wrote:
On 2017-09-08 21:22, Wols Lists wrote:
On 08/09/17 19:53, Carlos E. R. wrote:
The more of those 10 msec delays, the longer the whole wipe takes.

I tend to do 10MB just so I don't have to think about the capacity of
a single track. 10MB is plenty big to keep the disks write buffers
full, but small enough not to impact the system RAM.

Noted, thanks :-)

Note also that CHS (cylinders, heads, sectors), which used to define
track size, is now archaic and meaningless.

Yes, I know that.


Modern drives now use "constant angular velocity". Which may mean that
declaring a drive as 5200rpm or 7000rpm is also a little meaningless :-)

I don't understand this. You mean they change rotational speed (rpm)
based on some criteria?

They do NOT change rotational speed.

They do change transfer rates. Track 0 is near the outer
circumference so you have a lot more data passing under the disk head
per revolution.

Transfer rates can drop in half by the time your reading from the
tracks at the end of the drive (near the center).


Basically, the physical size of a sector is now constant. So a track
near the centre of a disk may have a capacity of 1MB, say. Move further
out, double the radius say, and you've doubled the physical length of
the track if I remember my maths right. So this track now will store
2MB. Move out the same distance again and that track will store 3MB.

Ah, yes.

Agreed, but I'm pretty sure you can't do 3x. There is dead space at
the center of the platter that isn't used. The radius of the outer
tracks is only about 2x the radius of the inner tracks.

Greg

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