[OpenIndiana-discuss] Are there any issues re ZFS on 2TB disks (from WD??) with large blocksizes?

[Richard L. Hamilton]

The question isn't what's wrong.  The question is how good the
support is for disks with 4K sectors - which includes the WD EARS
drives.

I think some (most?) such drives can emulate a drive with 512
byte sectors, but with a performance hit, esp. if the filesystem
has 4K or larger blocks that are mis-aligned relative to the
4K disk blocks.

I'm also under the impression that there may be some confusion or
inconsistency with how drives with 4K physical sectors (but the
capability to emulate a drive with 512 byte sectors) identify
themselves.

AFAIK, OpenSolaris etc have had 4K support for awhile now.
That doesn't mean it gets it right in all cases, given the
complications previously mentioned.

Probably it would work ok (give or take the performance hit)
for anything _other_than_ booting from.  That would involve
more stuff (ROM BIOS or OpenBoot, disk bootloader, etc) doing
the right thing, so I'd be less likely to be willing to gamble
on that.

For now, the Seagate 2TB drives, with plain old 512 byte sectors
avoid those complications.  I've got a pair of their SAS drives
(hooked up to an UltraSPARC III based Sun Blade 2000 via an LSI
SAS/SATA controller) and they work fine.

So...could you use the WD EARS drives?  Probably (give or take
booting), but as to the success and quality of the result, unless
someone specifically reports success on similar hardware to yours
(to include some indication that they're getting full performance
without the hit for read-modify-write), you may be in less than
fully tested territory for all I know...which isn't much, as
I haven't been following this issue closely.

The flip side: sooner or later, more or most new large drives will
probably be using 4K sectors.  So you'll eventually have to deal
with that anyway.  But given what you want to do _now_, you can
postpone that problem until maybe firmware and OS are all mature
enough to be counted on to handle it well, by choosing drives that
do not use 4K sectors.


On Feb 7, 2011, at 7:13 AM, Robin Axelsson wrote:

> Could someone enlighten me as to what is wrong with WD's disks, and particularly what's wrong with their EARS disks?
> 
> On 2011-02-07 12:52, Piotr Jasiukajtis wrote:
>> On Feb 7, 2011, at 10:26 AM, Hans J. Albertsson wrote:
>> 
>>> I'm planning to upgrade my two mirrored 500 GB SATAII rpool disks to 2x2TB  disks.
>>> 
>>> 
>>> A friend with some Sun experience claims there was some problem with using ZFS on large disks, possibly because of block size on some new large disks.
>>> 
>>> Can anyone enlighten me or point me to the proper docs or something?
>> Just avoid all WD EARS disks.
>> Seagate ST32000542AS and Hitachi seems to work fine.
>> 
>> --
>> Piotr Jasiukajtis | estibi | SCA OS0072
>> http://estseg.blogspot.com
>> 
>> 
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> 
> 
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