Was: iostat output; Now: Disk storage technologies

Matt,

>You can respond to me directly if you like - unless the list at large
>is interested in iSCSI on netapp.

I would very much like to keep this in the list..... The ground beneath us as far as storage is concerned is moving quite quickly, and most of us DBAs are still in the dark as far as Storage concepts and directions go. Many are not aware that there is a wide variety of solutions as far as disk storage is concerned, and the DBA world is just now getting a handle on the transition from DAS (Direct Attached Storage) to SAN (Storage Area Networks) or NAS (Network Attached Storage). And in comes comes iSCSI (or a combination of the above) to cloud the picture.... As far as I understand the technology, we have:

• DAS - Disks attached directly to a Server, including standlone extrenal boxes which may support different RAID versions (BAARF!!!) but attached to just the one server
• SAN - Disks in a Storage Array, frontended by cache and some intelligence, usually accessed via Fibre Channel and usually able to connect to many hosts via a switch; Presents opportunties for presenting varying levels of RAID (BAARF!!!), Storage-on-Demand, Host standby disks that can switch on automatically, Arrays that can 'dial-home' for replacement and other issues, Dynamically partition cache memory between read and write, Create mirrors for backup, provide for remote copies, etc.. etc... [This is obviously the high end storage and costs the most $$$]
• NAS - Disks in a Storage array, possibly frontended by cache and intelligence and other bells and whistles, presented to other servers via a form of specialized NFS. [NetApp is a special NAS technology that provides for WAFL and backup snapshots in a NAS but that is an entirely different discussion]

And now....

• iSCSI - (as I understand it) A bunch of disks (frontended by some intelligence) - made directly accessible via low level IP (rather than NFS at the higher layers), providing a poor man's version of NAS

As with everything else (including DBA skills!), you get what you pay for - SAN at the top end and (probably) iSCSI at the lowest end!

I am sure that I have made a lot of generalizations and Matt is cringing at my attempt to simplify everything, but is this a good start to our understanding of storage technology as it is now?

John Kanagaraj <><
DB Soft Inc
Phone: 408-970-7002 (W)

Listen to great, commercial-free christian music 24x7x365 at http://www.klove.com

• The opinions and facts contained in this message are entirely mine and do not reflect those of my employer or customers **

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