Can and when will SSDs + SATA replace FC/SAS?

Simon Seagrave ( asked, “How long do you think it’ll be before SSD will overtake SCSI as primary tier 1 SAN storage? Giving a new SSD and SATA tiered mix.”

Short answer: Yes, it will be SSDs + SAS and within 2 years.

The real quesion is when 15K RPM highspeed drives will be replaced with SSDs and 7.2K RPM high capacity drives.  SAS will probably end up replacing both FC and SATA in the majority of mid-range storage but the jury is still out on if this will happen in high-end arrays.

What are we talking about here? From an array design perspective, frequently accessed blocks of data should be served from ram and SSD.  SSDs have a much faster response time (microseconds vs. milliseconds) than traditional hard disk drives which enable this possibility.  The Sun Unified Storage platform was one of the first platforms to do this all in one array with their Hybrid Storage Pool design.  There are also some new appliances coming out like the Xcelasan from Dataram.  NetApp offers read accelerationt through their PAM 1 (Performance Acceleration Modules).  EMC will also start the transition at the LUN level with their implementation of FAST as described by Devang Panchigar.  This list is not meant to be comprehensive as I’m sure I have left out vendors and their roadmaps.

When will this happen? I expect the majority of storage vendors to implement this type of solution at the block level within the next 2 years based on current development cycles from most major storage vendors.  It will take some longer than others because of their architectures. It will be a key differentiating feature between vendors.  Beyond basic tiering between SSDs and high capacity disks we should see more advanced algorithms on what data and where to move it to.  I’ve followed journey of Sun’s ZFS  on the zfs-discuss mailing lists over the last year and have noticed that peculiar performance behaviors happen (write-pulsing) have required fine-tuning.


  1. sokratisg

    Nice prediction but what about SSD Write Endurance issues?

    If they get in the market of Tier 1 Storage, won’t they suffer from reliability issues? I am not talking of real “data loss” but disk the overall disk MTBF…

  2. edsai

    SSDs are already in the market and my feeling is that this would not be the case if they didn’t have good durability. There are features in almost all SSDs for wear-leveling but in EFD’s or “Enterprise Flash Drives” my impression is that they are made to last at least 3-5 years. Even then, in most tier-1 arrays you’re paying for maintenance and you have hot spares so the risk for data loss or drive failure mirrors what we see in standard hard drives today.

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