ZFS - moving from a zraid1 to zraid2 pool with 1.5tb disks
gpalmer at freebsd.org
Fri Jan 7 06:51:38 UTC 2011
On Thu, Jan 06, 2011 at 08:20:00PM -0800, Jeremy Chadwick wrote:
> 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?
Q Why does the HyperDrive5 have two SATA ports?
A So that you can split one 8 DIMM slot device into two 4 DIMM slot deivces and run them both in RAID0 using a RAID controller for even faster performance.
It claims SATA-300 (or SATA2 in the incorrect terminology from their website)
Note, I have no relation to hyperos systems and don't use their gear. I did
look at it for a while for journal/log type applications but to me the
price/performance wasn't there.
As it relates to the ACard, from memory the HyperDrive4 was ditched and
then HyperOS came out with the HyperDrive 5 which looks remarkably similar
to the ACard product. I was told by someone (or read somewhere) that
HyperOS outsourced it to or OEMd it from some Asian country, which
would fit if ACard was the manufacturer as they're in Taiwan.
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