[MacPorts] #60178: Don't use SSDs for buildbot workers

[MacPorts]

#60178: Don't use SSDs for buildbot workers
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  Reporter:  ryandesign      |      Owner:  admin@…
      Type:  defect          |     Status:  new
  Priority:  Normal          |  Milestone:
 Component:  server/hosting  |    Version:
Resolution:                  |   Keywords:
      Port:                  |
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Comment (by fhgwright):

 At the basic level, flash devices (as well as similar devices such as
 EPROMs and EEPROMs) rely on  very well-insulated static charges to store
 bits, whereas HDDs use magnetic domains, which are fundamentally more
 stable.  Both have been squeezing the bits more and more to get higher
 densities, but the HDDs have done a better job of improving the ECC to
 match than the SSDs.

 Part of my time at Google was in the flash storage area, so we had a lot
 of data on this issue, both operationally and from vendors.  We never used
 flash devices for primary storage, but only as performance-improving
 caches for data stored on HDDs.

 Assuming wear leveling, excess capacity directly translates into a lower
 P/E rate, but that's a rather expensive approach to take with devices that
 are already substantially more expensive per bit than HDDs.  Whether
 "SMART" monitoring can provide adequate early warning of failures remains
 to be seen, but it obviously didn't in the case of the failure that
 prompted the original ticket.  And of course, it's especially important to
 ensure that an SSD-based system never swaps.

 Granted, the performance of HDD-based Macs leaves a lot to be desired, but
 I suspect that a lot of this is due to poor scheduling and/or poor
 prioritization.  Apple would probably rather sell SSDs than improve the
 software.  And their "Fusion Drive" approach seems to be a much dumber way
 to use SSDs to improve HDD performance than the cache approach.

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Ticket URL: <https://trac.macports.org/ticket/60178#comment:2>
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