[OpenIndiana-discuss] beagleboard (arm) port?

[Jacob Ritorto]

	Good stuff fellows; thank you.  How bad are the failures resulting from 
non-ecc and missing cache flushes?  Can they put the pool into an 
unrecoverable state, or is it just a risk of dropping a minute's worth 
of writes or something like that?

	Again, this is a home archiving system with requirements of 1) data 
integrity, 2) minimal impact on electric bill over a year's run time and 
3) approximately no noise.



On 02/08/11 10:24, Jesus Cea wrote:
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> On 08/02/11 16:00, taemun wrote:
>> It's generally accepted that two things can break a ZFS pool: the use of
>> non-ECC RAM; and storage devices which do not respect cache flushes. You're
>> aiming for a system which is likely to have both. The latter by virtue of
>> the fact that most USB<=>  SATA controllers often don't respect sync
>> requests. Both of these can lead to broken metadata/uberblocks and hence a
>> broken pool.
>
> Caché flushes are important. The fist step I do when getting a new
> computer&disk is to write a small program (like 5 lines long) to write
> small (1 byte) data followed by a "fsync". If the number of fsyncs per
> second is too high, I know I can't trust the disk.
>
> Python code:
>
> """
> import os, time
> syncs = 10000
> f = open("zz","w")
> t = time.time()
> for i in xrange(syncs) :
>      f.write("a")
>      f.flush()
>      os.fsync(f)
> print "Realizamos %d transacciones por segundo" %(syncs/(time.time()-t))
> """
>
> Using 7200 RPM disks, the right value is around 120 transactions per
> second. If the value is far higher, "somebody" is lying to you about
> caché flushes.
>
> - --
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