zfs discuss - Feb 2009 - using USB memory keys for l2arc and zil

Would there be an advantage to using 4GB USB memory sticks on a home 
system for zil and l2arc?



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On Thu, Feb 5, 2009 at 8:15 AM, Karl Rossing <karlr at barobinson.com>
wrote:
> Would there be an advantage to using 4GB USB memory sticks on a home
> system for zil and l2arc?
Probably not. Most USB devices are slower than SATA disks.

-B

-- 
Brandon High : bhigh at freaks.com

> > Would there be an advantage to using 4GB USB memory sticks on a home
> > system for zil and l2arc?
> 
> Probably not. Most USB devices are slower than SATA disks.
Moreover, all USB devices are alower than most SATA disks.

-- 
 -D.    dgc at uchicago.edu    NSIT    University of Chicago

Would there be another inexpensive way to add zil and l2arc to a home system?

On 02/05/09, David Champion  <dgc at uchicago.edu>
wrote:
> > > Would there be an advantage to using 4GB USB memory sticks on a
home
> > > system for zil and l2arc?
> > 
> > Probably not. Most USB devices are slower than SATA disks.
> 
> Moreover, all USB devices are alower than most SATA disks.
> 
> -- 
> ?-D.??? dgc at uchicago.edu??? NSIT??? University of Chicago
> _______________________________________________
> zfs-discuss mailing list
> zfs-discuss at opensolaris.org
> http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
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> 
---
Karl Rossing
System Administrator
The Robinson Group






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On Thu, Feb  5 at 17:46, Karl Rossing wrote:
>   Would there be another inexpensive way to add zil and l2arc to a home
>   system?
Buy another 4GB of RAM for $50?  Wouldn''t that effectively grow the
arc?


-- 
Eric D. Mudama
edmudama at mail.bounceswoosh.org

On Thu, February 5, 2009 12:01, Eric D. Mudama wrote:
> On Thu, Feb  5 at 17:46, Karl Rossing wrote:
>>   Would there be another inexpensive way to add zil and l2arc to a home
>>   system?
>
> Buy another 4GB of RAM for $50?  Wouldn''t that effectively grow
the arc?
I had to replace a bad 1GB stick of ECC ram in my home fileserver the
other week.  That single 1GB stick was $100 locally; I haven''t priced
it
on the net, but I''d be surprised if it got as low as $50 from anywhere
respectable, the local place I bought mine is pretty good.

Which is to say, I think you''re drastically under-pricing 4GB of ram
even
for a home fileserver.
-- 
David Dyer-Bennet, dd-b at dd-b.net; http://dd-b.net/
Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/
Photos: http://dd-b.net/photography/gallery/
Dragaera: http://dragaera.info

On Thu, Feb 5, 2009 at 13:10, David Dyer-Bennet <dd-b at dd-b.net>
wrote:
>
> On Thu, February 5, 2009 12:01, Eric D. Mudama wrote:
>> On Thu, Feb  5 at 17:46, Karl Rossing wrote:
>>>   Would there be another inexpensive way to add zil and l2arc to a
home
>>>   system?
>>
>> Buy another 4GB of RAM for $50?  Wouldn''t that effectively
grow the arc?
>
> I had to replace a bad 1GB stick of ECC ram in my home fileserver the
> other week.  That single 1GB stick was $100 locally; I haven''t
priced it
> on the net, but I''d be surprised if it got as low as $50 from
anywhere
> respectable, the local place I bought mine is pretty good.
http://www.newegg.com/Product/Product.aspx?Item=N82E16820134332 is
$11.50 for 1gb of ECC DDR2 unbuffered Kingston.  I''d call Newegg
reuptable.

If ECC is required, then 4 gigs of memory cost:
http://www.newegg.com/Product/Product.aspx?Item=N82E16820134633 $94
FBDIMM (intel 5000 series et al)
http://www.newegg.com/Product/Product.aspx?Item=N82E16820148115 $48
Unbuffered (intel x38 chipset takes these, for example)
http://www.newegg.com/Product/Product.aspx?Item=N82E16820134273 $56
Registered (Opterons, et al)
and if you don''t have an ECC board:
http://www.newegg.com/Product/Product.aspx?Item=N82E16820148160 $38

Local stores are good when a part is needed quickly.  In my
experience, they''re not good when a part is needed cheaply.

Will

On Thu, Feb  5 at 12:10, David Dyer-Bennet wrote:
>Which is to say, I think you''re drastically under-pricing 4GB of
ram even
>for a home fileserver.
Okay, I was off by $10.

4 GB of ECC protected DDR2 for $40.99 (DDR2-533):
http://www.newegg.com/Product/Product.aspx?Item=N82E16820134312

The crucial DDR2-667 2x 2GB ECC protected RAM is $47.99

Even 4GB of ECC protected DDR2-667 FB-DIMM memory is $93.49:
http://www.newegg.com/Product/Product.aspx?Item=N82E16820134633



I''m sure if you''re running a more exotic setup in your
"home" server,
memory might be more expensive, but for basic ECC protected DDR2, the
prices are really cheap online.



-- 
Eric D. Mudama
edmudama at mail.bounceswoosh.org

On Thu, February 5, 2009 12:22, Will Murnane wrote:
> On Thu, Feb 5, 2009 at 13:10, David Dyer-Bennet <dd-b at dd-b.net>
wrote:
>>
>> On Thu, February 5, 2009 12:01, Eric D. Mudama wrote:
>>> On Thu, Feb  5 at 17:46, Karl Rossing wrote:
>>>>   Would there be another inexpensive way to add zil and l2arc
to a
>>>> home
>>>>   system?
>>>
>>> Buy another 4GB of RAM for $50?  Wouldn''t that effectively
grow the
>>> arc?
>>
>> I had to replace a bad 1GB stick of ECC ram in my home fileserver the
>> other week.  That single 1GB stick was $100 locally; I haven''t
priced it
>> on the net, but I''d be surprised if it got as low as $50 from
anywhere
>> respectable, the local place I bought mine is pretty good.
> http://www.newegg.com/Product/Product.aspx?Item=N82E16820134332 is
> $11.50 for 1gb of ECC DDR2 unbuffered Kingston.  I''d call Newegg
> reuptable.
Newegg is fine, definitely.  Most of the parts of my desktop computer came
from there, as it happens.

Okay, you win on the memory price; though I still frequently do not find
such prices myself when I look online, it seems to be variable.  But this
one is there now.  In fact I think I''ll bring the server up to 4GB
while
I''ve got this open.

I think that''s exactly what I need, DDR2 ECC unbuffered.
> Local stores are good when a part is needed quickly.  In my
> experience, they''re not good when a part is needed cheaply.
Well, I already allowed for a 2x difference in my own guesstimate; that
just turned out to be wrong by *another* factor of 4.
-- 
David Dyer-Bennet, dd-b at dd-b.net; http://dd-b.net/
Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/
Photos: http://dd-b.net/photography/gallery/
Dragaera: http://dragaera.info

>>>>> "wm" == Will Murnane <will.murnane at
gmail.com> writes:
    wm> http://www.newegg.com/Product/Product.aspx?Item=N82E16820148115
    wm> $48 Unbuffered (intel x38 chipset takes these, for example)

yeah for some reason they only make the slow speeds in unregistered
ECC which is annoying.  I think AMD has just released or is about to
release the desktop CPU''s with the faster memory controller, but you
can''t get faster ECC sticks for them, only fast non-ECC.  Also I am
worried the ECC error is not handled by the whole software
stack---maybe some ``no, seriously, check ECC shit'''' knob is
not
twisted by the cheapo Chinese gamer BIOS, and it is only BIOS writers
who worry about this bit since they are supposed to enumerate all the
RAM sticks and their SROM''s, not the OS.  Or the CPU / northbridge
supports ECC but the pins aren''t wired on the motherboard.  Or
technically Phenom II checks ECC, but the driver in the OS only works
with older Opterons, so you are hitting ECC errors all the time but
when you hit one the machine just powers down, or silently continues
healing errors with no warning until the stick goes totally bad thus
behaving in effect exactly like non-ECC RAM.  Or something.  Also
there''s the question *when* is the error detected---when the ARC grows
that big, or does the ``memory scrubber'''' thread or
``background page
zeroing'''' thread find it, does the error put the machine into
syslog/fmd convulsions using up all disk bandwidth with synchronous
writes to some XML file ``ECC error, detected!  detected
again!'''',
u.s.w.  I need some kind of deliberately broken ECC test stick.  With
ZFS you can scribble on disks then scrub them, but with ECC on modern
CPU/motherboards it is kind of like reading the future in chicken guts
and hoping you got it right.
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On Thu, 5 Feb 2009, Miles Nordin wrote:
>>>>>> "wm" == Will Murnane <will.murnane at
gmail.com> writes:
>
>    wm> http://www.newegg.com/Product/Product.aspx?Item=N82E16820148115
>    wm> $48 Unbuffered (intel x38 chipset takes these, for example)
>
> yeah for some reason they only make the slow speeds in unregistered
> ECC which is annoying.  I think AMD has just released or is about to
> release the desktop CPU''s with the faster memory controller, but
you
> can''t get faster ECC sticks for them, only fast non-ECC.  Also I
am
It is perhaps best to not confuse smoke with mirrors.  The Intel CPUs 
require the higher-clocked power-hungry fully-buffered memory to make 
up for architectural problems.  The Mac OS-X pin-wheels will not spin 
any faster with the higher speed memory.

I suggest that stream benchmark results be consulted rather than a 
megahertz rating on a memory chip.  Another useful benchmark is the 
SPEC OpenMP benchmarks.  Actual system performance is all that 
matters.  Anything else is just useless noise.

Bob
=====================================Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/