RAID 7 disk array platforms versus earlier RAID 4 & 5

RAID 7 disk array platforms versus earlier RAID 4 & 5

Post by Michael Willet » Fri, 23 Oct 1992 00:03:51



Regarding the additional question posted about how RAID 7 differs from the
earlier RAID 4, I checked with Storage Computer about their posting of
their explanation.  It turns out that their key people there have been
concentrating on the DG Users' Meeting where Storage Computer was
participating.  (Apparently they don't feel the DG Clarion RAID is much
competition.)  Now that the DG meeting is over, they said they'd prepare
some comments.  I'll follow up on that.  If they don't have their
network connection going in time, maybe I'll post their comments from
here, if they're not too long.   (Meanwhile, if anyone wants any info on
the RAID 3 Wang has just announced for our VS installed base, let me
know.  This RAID 3, which is from a different RAID manufacturer, was
selected because it most closely matches our VS architecture, producing
optimized performance for our VS minicomputer product line.)


Regarding the question about how RAID 7 differs from the earlier RAID 5,
all I personally know is what I saw in the Storage Computer RAID 7
brochure which reads as follows:

"Question. I am confused.  For transaction processing, how can a RAID 7
deliver higher performance than the operation of a RAID 5?"

"Answer. One reason mentioned earlier is that RAID 7 will always have a
higher average number of concurrent events being processed than a RAID 5
with the same number of drives.  Another reason is a basic flaw in the
RAID 5 architecture.  By rotating parity and interleaving these parity
sectors or blocks with the data, RAID 5 increases the average data
access time for every read and write, because it has to seek across more
cylinders for the same data.  If a RAID 7 has a data access time equal to
1, then a RAID 5 with the exact same drive will need 1+(1/N) time.  Granted
that this penalty declines with more drives in the array, but it never goes
away.  RAID 5 will always have to seek data across more cylinders; that
always takes more time, and therefore RAID 5 will always be slower than a
basic RAID 7.  Also the StorComp Operating System speeds up transaction
processing by the sophisticated management of the Principle of Locality."

Generally speaking, it would seem to be important to have the key RAID 7
executives themselves provide detailed information on such RAID 7 questions
via the network, so we can get the full story.  It would be interesting if
we could get long term RAID 7 OS strategy information from them also.

As far as interest in Japanese investment in the firm goes, I understand
that there isn't any yet.  Logical candidates would seem to be Fujitsu,
Hitachi, and Toshiba, I suppose.  Currently, the firm is private so it is
not possible to buy shares on the US or Japanese exchanges.  (The head of
their Japanese distributor is the former chairman of Sony Computer Systems.)
--------------------------------

Regarding John Scoggin's request for information on RAID systems for
VINES, Storage Computer of Nashua, N.H. is currently showing its new high
performance SCSI-RAID 7 disk array platforms at the September Banyan Users
Meeting.  They work equally well with NetWare, IBM systems, workstations,
the VAX, etc.

Standards-based, RAID 7 is designed for enterprise-wide computing and
overcomes performance limitations of earlier RAID architectures, providing
a  "real world sustained application performance improvement of 200% to
400%" and dropping the cost of storage to 16 cents/MB.  Their brochures
say they can "mix and match" up to 48 SCSI commodity (3.5 or 5.25 inch)
drives, up to 150 GB.  The RAID 7 disk array platforms come with an embedded
operating system and up to 12 SCSI-2 based host interfaces.  Besides servers,
Storage Computer's RAID 7 disk array platforms can connect to workstations
and midrange systems in addition to IBM's.  Multiple CPUs can be attached to
same disk array platform.

The RAID 7 platforms come with up to 256 MB of cache, eliminating any
reason for using performance-damaging CPU main memory disk RAM.

The drives are "hot plugable" for uninterrupted, transparent operation,
with a hot standby drive automatically replacing a failed drive.

There was a lot of activity yesterday at the Storage Computer RAID 7 booth
at the Banyan show as I walked by.  They were demoing what happens if a
drive goes down, showing the backup drive taking over.

For further information on Storage Computer's RAID 7 for various systems, the
key contact is indicated to be John O'Brien, Director of Technical Services,
at Tel. 603-880-3005 or FAX 603-889-7232.  He's the "guru" of RAID 7 and
a leading RAID industry figure.


 
 
 

1. Raid 7 Versus Earlier Raid 4

Regarding availability of RAID 7, Dave Goldblatt at Clarkson University
writes:

No, these RAID 7 disk array platforms are not available from us here
at the new Wang Labs.  You would have to get them directly from Storage
Computer in Nashua, New Hampshire, or via their European headquarters
in Frankfurt, or their European/Asia/Pacific distributors.  Here at the
new Wang Labs we are reselling a RAID 3 from another major vendor, because
the architecture more closely matches that of our VS minicomputers
(both those already installed and the new VS high-end models that have
been coming out recently.)   I'll be happy to find some technical RAID
reports on the Wang VS RAIDs for those people interested.

anything else on it in the press.

Actually they've published a number of technical articles in the
literature.  They seem to prefer to publish more technical material,
rather than marketing blurbs.  There have been some recent, favorable
reviews of their products in Corporate Technology Review, Open Systems
Today, and iX magazine from Germany.  People interested could probably
get copies by calling them at 603-880-3005.

In general, they seem to prefer demoing their products at user group
meetings, rather than sending out press releases.  They have recently
had booths at the Banyan, Wang, and Sun users groups meetings, among
others.


2. SymbolicLink between application and driver isn't working.

3. Raid 7 versus earlier Raid 4

4. Dets 3.56 and GeForce nuke FS2K for me...

5. Raid 7 Versus Earlier Raid 4

6. DECserver - Async conn.

7. RAID 7 Disk Array Platform Meetings in Halle 1, 5D4--CEBIT

8. ZIP / JAZ Removable Media ???

9. RAID 7 vs. Earlier Raid 4

10. Firewire RAID 0 or RAID 1 (dynamic disks) on Win2K

11. IBM now does RAID 7 for AS/400 & other IBM platforms

12. IBM now does RAID 7 service for AS/400 & other IBM platforms

13. FS: EMC Symmetrix 3430 RAID Disk Array