ZFS - moving from a zraid1 to zraid2 pool with 1.5tb disks

Jeremy Chadwick freebsd at jdc.parodius.com
Fri Jan 7 04:20:04 UTC 2011

On Fri, Jan 07, 2011 at 01:40:52PM +1100, Jean-Yves Avenard wrote:
> On 7 January 2011 12:42, Jeremy Chadwick <freebsd at jdc.parodius.com> wrote:
> > DDRdrive:
> >  http://www.ddrdrive.com/
> >  http://www.engadget.com/2009/05/05/ddrdrives-ram-based-ssd-is-snappy-costly/
> >
> > ACard ANS-9010:
> >  http://techreport.com/articles.x/16255
> >
> > GC-RAMDISK (i-RAM) products:
> >  http://us.test.giga-byte.com/Products/Storage/Default.aspx
> >
> > Be aware these products are absurdly expensive for what they offer (the
> > cost isn't justified), not to mention in some cases a bottleneck is
> > imposed by use of a SATA-150 interface.  I'm also not sure if all of
> > them offer BBU capability.
> Why not one of those SSD PCIe card that gives over 500MB/s read and write.
> And they aren't too expensive either...

You need to be careful when you use the term "SSD" in this context.
There are multiple types of SSDs with regards to what we're discussing;
some are flash-based, some are RAM-based.

Below are my opinions -- and this is getting WAY off-topic.  I'm
starting to think you just need to pull yourself up by the bootstraps
and purchase something that suits *your* needs.  You can literally spend
weeks, months, years asking people "what should I buy?" or "what should
I do?" or "how do I optimise this?" and never actually get anywhere.
Sorry if it sounds harsh, but my advice would be to take the plunge and
buy whatever suits *your* needs and meets your finances.

HyperDrive 5M (DDR2-based; US$299)
1) Product documentation claims that "the drive has built-in ECC so you
can use non-ECC DDR2 DIMMs" -- this doesn't make sense to me from a
technical perspective.  How is this device doing ECC on a per-DIMM
basis?  And why can't I just buy ECC DIMMs and use those instead (they
cost, from Crucial, $1 more than non-ECC)?

2) Monitoring capability -- how?  Does it support SMART?  If so, are the
vendor-specific attributes documented in full?  What if a single DIMM
goes bad?  How would you know which DIMM it is?  Is there even an LED
indicator of when there's a hard failure on a DIMM?  What about checking
its status remotely?

3) Use of DDR2; DDR2 right now is significantly more expensive then
DDR3, and we already know DDR2 is on its way out.

4) Claims 175MB/s read, 145MB/s write; much slower than 500MB/s, so
maybe you're talking about a different product?  I don't know.

5) Uses 2x SATA ports; why?  Probably because it uses SATA-150 ports,
and thus 175MB/s would exceed that.  Why not just go with SATA-300,
or even SATA-600 these days?

6) Form factor requires a 5.25" bay; not effective for a 1U box.

DDRdrive (DDR2-based; US$1995)
1) Absurdly expensive for a product of this nature, even more so
because the price doesn't include the RAM.

2) Limited to 4GB maximum.

3) Absolutely no mention if the product supports ECC RAM or not.

4) PCIe x1 only (limited to 250MB/sec tops).

5) Not guaranteed to fit in all chassis (top DIMM exceeds height of
   the card itself).

ACard ANS-9010 (DDR2-based)
Looks like it's either identical to the HyperDrive 5, or maybe the
HyperDrive is a copy of this.  Either way...

I'm not even going to bother with a review.  I can't imagine anyone
buying this thing.  It's part of the "l33td00d" demographic.

| Jeremy Chadwick                                   jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.               PGP 4BD6C0CB |

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