[rescue] FreeBSD and ZFS, was Re: 3ware raid

Zachary Giles zgiles at gmail.com
Thu Aug 4 12:39:48 CDT 2011

Just a report back about the Marvell true JBOD controllers vs the
3ware cards I had (that originally started this discussion).
The Marvell controllers feel really smooth. Bonnie++ reports about
1.5x the performance with them and Solaris is very happy. I recommend
them. Same drives and everything.

On Thu, Aug 4, 2011 at 10:01 AM, Richard Zawaski <zski128 at yahoo.com> wrote:
> Those systems are BSD/Linux correct? DeDup on Solaris worked great in our
> case. Saved lots of IO to the disk and actually sped up file access. DeDup
> with ZFS on anything else but Solaris I would not trust.
> ________________________________
> From: JP Hindin <jplist2008 at kiwigeek.com>
> To:
> The Rescue List <rescue at sunhelp.org>
> Sent: Thursday, August 4, 2011 12:36 PM
> Subject: Re: [rescue] FreeBSD and ZFS, was Re: 3ware raid
> On Thu, 4 Aug 2011,
> N. Miller wrote:
>> You need to be very careful with dedup.  IMO, I would never
> implement it
>> without first doing extensive tests with a copy of the real
> data I expected to
>> see in production.  You need lots of RAM on top of the
> normal "lots" of RAM
>> required by ZFS, because the entire dedup table is kept
> in resident memory.
>> Also, you can't revert without doing a dataset (or
> maybe pool, not sure if
>> this is a pool-wide or dataset level config)
> rebuild.  Example: you can turn
>> on compression, anything written to the
> dataset while compression is on will
>> be compressed.  You can then turn off
> compression and anything written to disk
>> will not be compressed, but
> compressed data can still be read, etc.  With
>> dedup, it's ON, and you can
> only turn it off by sending all the data to a
>> dataset with dedup OFF.
> We
> "accidentally" ended up having de-dupe turned on in our various Nexenta
> (ZFS)
> arrays and it caused no end of troubles with false disk failures,
> data loss
> and all sorts of crazy stuff.
> As soon as we verified the issue and turned
> de-dupe off the issues all
> vanished and we've had a set of solid Nexentas ever
> since (12mos and
> counting on three Nexentas with about 120T of storage between
> them).
> I know it's anecdotal, but it was a total nightmare for us.
> - JP
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Zach Giles
zgiles at gmail.com

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