Re: [9fans] Petabytes on a budget: JBODs + Linux + JFS

[Bakul Shah <bakul+plan9@bitblocks.com>]

On Mon, 21 Sep 2009 16:30:25 EDT erik quanstrom <quanstro@quanstro.net>  wrote:
> > > i think the lesson here is don't by cheep drives; if you
> > > have enterprise drives at 1e-15 error rate, the fail rate
> > > will be 0.8%.  of course if you don't have a raid, the fail
> > > rate is 100%.
> > >
> > > if that's not acceptable, then use raid 6.
> >
> > Hopefully Raid 6 or zfs's raidz2 works well enough with cheap
> > drives!
>
> don't hope.  do the calculations.  or simulate it.

The "hopefully" part was due to power supplies, fans, mobos.
I can't get hold of their reliability data (not that I have
tried very hard).  Ignoring that, raidz2 (+ venti) is good
enough for my use.

> this is a pain in the neck as it's a function of ber,
> mtbf, rebuild window and number of drives.
>
> i found that not having a hot spare can increase
> your chances of a double failure by an order of
> magnitude.  the birthday paradox never ceases to
> amaze.

I plan to replace one disk every 6 to 9 months or so. In a
3+2 raidz2 array disks will be swapped out in 2.5 to 3.75
years in the worst case.  What I haven't found is a decent,
no frills, sata/e-sata enclosure for a home system.