gvinum raid5 vs. ZFS raidz
daniel
DStaal at usa.net
Sat Aug 30 13:05:21 UTC 2014
On 2014-08-29 18:47, Scott Bennett wrote:
> Paul Kraus <paul at kraus-haus.org> wrote:
>
>> On Aug 28, 2014, at 2:36, Scott Bennett <bennett at sdf.org> wrote:
>>
>> > Paul Kraus <paul at kraus-haus.org> wrote:
>> > Are you using any drives larger than 1 TB?
>>
>> I have been testing with a bunch of 2TB (3 HGST and 1 WD). I have been
>> using ZFS and it has not reported *any* checksum errors.
>>
> What sort of testing? Unless the data written with errors are
> read back,
> how would ZFS know about any checksum errors? Does ZFS implement
> write-with-
> verify? Copying some humongous file and then reading it back for
> comparison
> (or, with ZFS, just reading them) ought to bring the checksums into
> play. Of
> course, a scrub should do that, too.
No write with verify that I know of (at least, this type of verify) but
any read should brings the checksums into play. (And scrub, of course.)
> As soon as I can get two more 2 TB drives and set them up under
> ZFS,
> I intend to try the equivalent of that. Because drives cannot be added
> to
> an existing raidzN, I need to wait until then to create the 6-drive
> raidz2.
> However, that original 1.1 TB file is currently sitting on one of the
> four
> drives I already have that are intended for the raidz2, so that file
> will
> be trashed by creating the raidz2. The file is a dump(8) file of a 1.2
> TB
> file system that is nearly full, so I can run the dump again with the
> output
> going to the newly created pool, after which I can try a
> "dd if=dumpfile of=/dev/null" to see whether ZFS detects any problems.
> If
> it doesn't, then I can try a scrub on the pool to see whether that
> finds any
> problems.
> My expectation is that I will end up contacting one or more
> manufacturers
> to try to replace at least two drives based on whatever ZFS detects,
> but I
> would be glad to be mistaken about that for now. If two are that bad,
> then
> I hope that ZFS can keep things running until the replacements show up
> here.
Just for the testing, you can set up a one-drive zpool. ZFS wouldn't be
able repair the error in that case (unless you set the 'copies'
property, but then you'll need more disk space for the write; basically
that would mean writing a backup to the same drive), but it will still
be able to detect it.
Daniel T. Staal
---------------------------------------------------------------
This email copyright the author. Unless otherwise noted, you
are expressly allowed to retransmit, quote, or otherwise use
the contents for non-commercial purposes. This copyright will
expire 5 years after the author's death, or in 30 years,
whichever is longer, unless such a period is in excess of
local copyright law.
---------------------------------------------------------------
More information about the freebsd-questions
mailing list