Was: iostat output; Now: Disk storage technologies
- From: John Kanagaraj <john.kanagaraj@xxxxxxx>
- To: "'oracle-l@xxxxxxxxxxxxx'" <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 29 Apr 2004 10:05:59 -0700
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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