Re: IBM in talks to buy Sun
On Mar 20, 11:25 am,
Lew wrote:
The notion that you can simply hot-swap disks if they fail in a high-
volumn production environment is wacky.
Eric Sosman wrote:
The notion of hot-swapping failed disks is certainly not wacky=
..
Perhaps it's the "simply" that you consider wacky? That might
make sense.
Yes, it was the "simply".
Lew:
It's not just data, it's service time that's valuable. Most such
installations cannot afford downtime, at least not much. Disk
failures are a major fubar. The motivation for RAID itself proves
that - it increases the cost per storage amount in favor of higher
reliability.
Eric Sosman wrote:
Right. And a RAID unit that survives a disk failure but sti=
ll
must be taken out of service for repair is less reliable than one
in which you can replace the failed drive without interruption.
True.
However, I have yet to meet an operations person who appreciates a
hard-drive failure, much less repeated hard-drive failures, even when
you can hot-swap failed drives. Nor do facilities managers generally
consider only the price of a hard drive without at least thinking
about reliability. The reason the more expensive drives and drive
arrays continue to sell is that customers see value in them.
Lew:
The suggestion that one can buy inferior hardware in quantity and just
swap in new pieces when something breaks betrays an utter lack of
understanding of the problem. If that idea worked, the people
responsible for those data centers would do that, but it doesn't and
they don't.
Eric Sosman wrote:
Tradeoffs certainly exist. It is not a given that the same =
trade
makes sense for all circumstances.
I never, ever make sweeping generalizations. :-)
Seriously, it is more common than not for data centers to purchase
more reliable, faster hard drives rather than simply opting for the
cheapest. The odds that they'll spend more go up with the volume and
value of their data, with the volume of access to those data, and with
the importance they attach to uptime.
Over the years I've dealt with many businesses who've tried to go with
less expensive hardware, be it disk drives, network cards, PCs or
whatnot, only to regret that and switch to more expensive but more
reliable choices. Every large-scale data center I've worked with, and
most medium- and even small-scale ones, tended to favor reliability
and performance over price in their evaluations.
--
Lew