hadoop-common-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Raghu Angadi <rang...@yahoo-inc.com>
Subject Re: RAID-0 vs. JBOD?
Date Thu, 10 Apr 2008 20:31:54 GMT

Ted Dunning wrote:
> 
> I haven't done a detailed comparison, but I have seen some effects:
> 
> A) raid doesn't usually work really well on low-end machines compared to
> independent drives.  This would make me distrust raid.
> 
> B) hadoop doesn't do very well, historically speaking with more than one
> partition if the partitions are not roughly equal in size.  Quite frankly,
> it doesn't even do all that well with datanodes that have radically
> different storage availability.
> 
> C) with raid-0, if you lose either drive, you lose both.  With separate
> partitions, you can lose one drive and retain the other.
> 
> These lead to opposite conclusions, so I don't know what to recommend.  If I
> had to choose, I think I would do without RAID.

D) Out of 5 disks, if one of them is slow (not that uncommon), then 
whole RAID will run only as fast that disk.

On smaller cluster (<100 nodes), RAID is simpler over all since 
probability of bad disks is less.

Raghu.

Mime
View raw message