Discussing all things virtualization and storage in the data center.

History being re-written?

My first external fibre attached storage was in the mid 1990's.  It was a Sun RSM200 (I think) and I used Veritas VxVM 2.4 (or whatever Sun called it then).  I was impressed.  I had all these disks in trays (9 disks per tray, 9.1 GB disks and 5 trays).  That was pretty big storage in those days.  I was able to carve up these disks to one or two E4000 servers (as thats how many ports were on the controllers the RSM2000 had).  I had the option of RAID 0, RAID 1 and RAID 5.  RAID 0 was never really an option because I was running mission critical database servers for the countries leading stock broker.  I often wondered why RAID 0 was ever an option.

Today, I overhead a colleague at work talking about different RAID levels.  He was talking about RAID 0 and striping.  I thought, what?  RAID 0 is concatenation.  The options with Veritas for RAID 0 (and if I recall properly Sun Disksuite/LVM/SVM) were always called RAID 0 concatenation.  The person then promptly went to wikipedia and showed me that RAID 0 was striping.  He said, concatenation was JBOD????.  The discussion went on for sometime but it seems he was abviously right even though sites related to Veritas said RAID 0 was concatenation (and I discovered striping).

The following is from a VXVM 4 training website.

  • List the common features of each supported RAID level including:
    • Concatenation - RAID 0
    • Striping - RAID 0
    • Mirroring - RAID 1
    • Mirrored Stripe - RAID 0+1
    • Mirrored Concatenation - RAID 0+1
    • Striped Mirror - RAID 1+0
    • Concatenated Mirror - RAID 1+0
    • Striping with distributed parity - RAID 5
  • NOTE:  RAID Levels 2, 3, 4 and 6 are/were not available with VxVM at that time and probably still are not.

    I got to thinking that perhaps vendors had somehow changed the concept of RAID.  So, to cut a long story short, who has changed history with the concept of RAID 0 being striping and not even mentioning concatenation.  Has Sun/Veritas had it wrong for the last 11 years that I know of.  Has HP in particular come up with RAID 0 being striping only and concatenation not even being a RAID option anymore.  The reason I say HP is that they are the major Intel/AMD based server maker and have been for sometime.  So, any young person (and they are always right) getting into IT and invariably Windows would only know about what HP say.

    I felt a bit stupid being the storage specialist at work and finding out that I was WRONG about concatenation....  11 years of being wrong???


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