An Oracle blog about ZFS Storage

  • December 11, 2014

I Like Big Blocks and I Can Not Lie (1992 vs 2014)

A relatively under discussed
feature of the ZFS Storage Appliance is it's ability to use a variable
block size for the storing of files. The "record size" on ZFS can be set
anywhere from 512 bytes all the way up to 1 megabyte. This differs from
the likes of NetApp and Isilon which respectively use 4K and 8K fixed
block sizes. 

When NetApp launched back in 1992 it was a good
approach to base things around 4K as IOPS/GB were excellent. In fact,
1992 saw the release of the industry's first 7,200 RPM drive, Seagate's
Barracuda ATA, coming in at a whopping 2.5GB with approximately with 40
IOPS/GB. However, put this in contrast to today's 4TB 7,200 RPM drives
at 0.025 IOPS/GB and a 4K fixed block size starts to make a lot less

Though IOPS/GB have dropped with each generation of HDD,
what is great with modern HDD is that with increasing areal density
throughput speeds have steadily improved, but to make use of that speed
you really need to be making the most of those limited IOPS. With ZFS,
using a large record size of 1MB does exactly that, as shown by the
incredible SPC-2 throughput benchmarks results provide by both the Oracle ZS3-2 & ZS3-4 Storage Appliances.

you've got a lot of data to process, such a geological analysis, VFX
rendering, driving a data warehouse or simply doing backups you're going
to love working with a large block size.

Let me finish by paraphrasing Sir Mix-a-Lot's hit song "I... like... big blocks and I can not lie, you other vendors can't deny"...
if you end up with that tune stuck in your head for the rest of the
day, I apologise. However, it's somewhat apt that this single was also
first released in 1992 ;-)

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