[OpenAFS] Overview? Linux filesystem choices

[Stephan Wiesand]

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On Sep 30, 2010, at 15:40 , Gary Buhrmaster wrote:

> On Thu, Sep 30, 2010 at 05:19, Stephan Wiesand =
<stephan.wiesand@desy.de> wrote:
> ...
>=20
>> Anyway, the next best option if ZFS is not available is to run parity =
checks on all your arrays regularly.
>=20
> Perhaps it is the best one can do, but be aware that
> a (rare, but real) failure mode of disks is that they
> return the contents of a different block than asked.

I know :-)

> No amount of background scrubbing fixes that
> unless the failures are solid (and they are usually
> not).

As I said: my experience is that a disk either does it or not. If it =
does, it does so when it's new and shiny. But yes, I'd still like to =
have ZFS's data protection.

> That does not even include the issue that
> most disk controller data paths (and cache
> memories) are not even parity checked, and
> bit flipping can happen there too.

right :-(

> NetApp recognized this and dealt with it with
> the WAFL file system years ago.  They actually
> wrote a checksum for the block and the block id
> onto disk and checked when they read a block
> back.
>=20
> Getting back the data your wrote is a hard
> problem.  ZFS presumes that everything
> downstream of it will (eventually) fail.  There
> is overhead there, but it does solve a set
> of problems that other solutions do not.
> (And the highly paranoid presume ZFS will
> fail, so take different precautions).
>=20
> As Jeff stated, if you really care about your
> data, you need ZFS.
> Gary

Alas, ZFS is only available with an OS that's *really* troublesome to =
maintain. Frankly, I wouldn't mind the cost. But those patch orgies make =
Solaris a no-go here. And two decades after the invention of RPMS and =
DEBs, they come up with ... IPS. Sorry, no matter how good and =
exceptional ZFS may be, it's just not worth it...

Stephan


--=20
Stephan Wiesand
DESY -DV-
Platanenenallee 6
15738 Zeuthen, Germany


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