Friday, December 30, 2011

[IT] My IT wishlist for 2012 (part 1 - SSD Tiering)

My IT wishlist for 2012 (part 1 - SSD Tiering) :

Hybrid-Storage in servers

I've been a big fan of SSD technology from the very beginning, I've run or tested :
- Samsung's Hybrid HDD (a failure)
- HyperDrive's 4 and 5 (RAM-based SSD) with battery and CompactFlash backup => works fine
- Gigabyte i-Ram (RAM-based SSD) battery-backed => works fine but limited capacity
- Intel X25-E and HP Gen1 SSDs => works fine, but many failure with database workloads even though they are SLC
- Fusion-IOs PCIe => perfect, but expensive
- Pliant (now SanDisk) SSDs => perfect too, less expensive than the Fusion-IOs
- various consumer-class SSDs (Crucial, RunCore, Intel)

As SSD prices go down and need for fast and big data processing, it's more and more relevant to use tiered-storage (also called hybrid-storage or Tier-0 storage) :

This technology is coming from high-end SAN systems like Pillar Data system's and others...

The idea is pretty simple, while your favorite RAID controller's max RAM cache did increase over time, from 128MB (2000's) to 256MB and now 512MB (LSI) and 1GB (HP) or even 4GB (Areca). This amount of cache helps but can't cope with today's need for ultra-fast and extra-large cache in front of your favorite SAS or SATA drives... This is where the Hybrid cache comes and efficiently caches a good part of the most used data you are using. You then have 3 layers of cache in front of the "slow" drives : OS caching (mostly read), RAID Ctrl RAM cache (often 75% write, 25% read), SSD cache (read and write).

A bit of reading on this topic (all from LSI) :

Now imagine a server like the Dell PowerEdge C1100 with 2 x 200G SLC SSDs and 8 x 900G SAS drives, that's a nice database server in 1U...

Dell also announced that they will be able to provide SSD 2.5" drives which will be directly connected as PCIe cards in their next-gen servers (a kind of hot-plug Fusion-IO). That's nice but for some reasons (probably lack of space inside the 1U server) they won't allow 2 x PCIe-SSD + 8 x SAS HDD, only 2 SSD + 4 SAS HDD...

Anyway, this is clearly our future !

While on the consumer market there has been many failure to do this, probably mainly because they were trying to fit everything inside the HDD itself, there seems to be new approaches to the issue which will probably be more successful :
- Hybrid drive with "Tiering controller" + SSD + HDD on a PCIe-card : OCZ RevoDrive Hybrid PCI Express
- Software-based Tiering as seen on OCZ Synapse Cache which is basically a classic SSD Drive + Nvelo's Dataplex software (