Re: else or Debian (Re: ZFS performance (was: Re: deduplicating file systems: VDO with Debian?))
hw wrote:
> On Thu, 2022-11-10 at 20:32 -0500, Dan Ritter wrote:
> > Linux-Fan wrote:
> >
> >
> > [...]
> > * RAID 5 and 6 restoration incurs additional stress on the other
> > disks in the RAID which makes it more likely that one of them
> > will fail. The advantage of RAID 6 is that it can then recover
> > from that...
>
> Disks are always being stressed when used, and they're being stessed as well
> when other types of RAID arrays than 5 or 6 are being rebuild. And is there
> evidence that disks fail *because* RAID arrays are being rebuild or would they
> have failed anyway when stressed?
Does it matter? The observed fact is that some notable
proportion of RAID 5/6 rebuilds fail because another drive in
that group has failed. The drives were likely to be from the
same cohort of the manufacturer, and to have experienced very
similar read/write activity over their lifetime.
To some extent this can be ameliorated by using disks from
multiple manufacturers or different batches, but there are only
three rotating disk makers left and managing this is difficult
to arrange at scale.
> > Most of the computers in my house have one disk. If I value any
> > data on that disk,
>
> Then you don't use only one disk but redundancy. There's also your time and
> nerves you might value.
It turns out to be really hard to fit a second disk in a laptop,
or in a NUC-sized machine.
> > I back it up to the server, which has 4 4TB
> > disks in ZFS RAID10. If a disk fails in that, I know I can
> > survive that and replace it within 24 hours for a reasonable
> > amount of money -- rather more reasonable in the last few
> > months.
>
> How do you get a new suitable disk within 24 hours? For reasonable amounts of
> money? Disk prices keep changing all the time.
My local store, MicroCenter, has --- 20ish 4TB disks in stock. I
can go get one in an hour.
Amazon will ship me a suitable drive next day or faster -- I
have ordered some items in the morning and received them before
nightfall -- at a lower cost, but at the price of enriching
Bezos.
-dsr-
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