[OT] Re: [CentOS] Centos 4.2 and Boot/Root on RAID? -- avoid blanket statements on RAID hardware

Bryan J. Smith thebs413 at earthlink.net
Thu Oct 20 17:09:07 UTC 2005

Les Mikesell <lesmikesell at gmail.com> wrote:
> Often it is because for the extra money, you get no extra
> features except being locked into some particular vendor's
> product

As I have pointed out before, that depends on the vendor.

Please don't blanket all vendors as the same.  Some vendors
have 6+ years of proven inter-product hardware RAID volume
compatibility with excellent Linux support.

> With software RAID1 you can pull out any single disk and
> recover the data on any machine with a similar interface
> type.

Not always.  SCSI controllers can very in their format, and
even ATA can be suspect.  Rare is this case, yes.  But I have
run into it -- especially with SCSI.

> With a raid controller, if the PC or controller fails
> you'll have to have exactly the same model to ever access
> those drives again -

Once again, I will ask you to not blanket all vendors as

3Ware has maintained 6+ years of inter-model volume
compatibility -- far more, far better and far longer than
Linux's MD/LVM which has gone through several, significant
changes.  This is indisputable, despite the insistance of
some in the MD/LVM community -- it's more about ignorance of
3Ware than usage (or improper usage of 3Ware cards for
software RAID, instead of using their hardware RAID

> and you may or may not have the tools to observe the status
> and 'smart' condition of the drives and to rebuild the
> mirrors online.

Any "quality" vendor has tools to not only rebuild the volume
on-line, but the rebuild is done in hardware.  And has many
people have pointed out, the hardware can pick up where it
left off regardless of any power, OS or other transient

As far as monitoring tools, yes, many vendors have their own.
 At the same time, nearly all vendors send standard syslog
messages.  A few are even integrating with smartd and mdadm,
and most of the reason they did not prior is because of a
lack of their standardization (e.g., mdadm).

Again, be careful with blanket statements.  There are vendors
with good track records and vendors with poor track records
-- both in maintaining inter-model volume compatibility as
well as Linux support.

-- Bryan

SIDE NOTE:  It's clear to me that 3Ware's introduction of the
new Escalade 9550 series with an embedded PowerPC signals
that their legacy ASIC was not sufficient for DRAM and RAID-5
in the preceding Escalade 9500 series.  I've said it before
and I'll say it again, 3Ware Escalade 7000/8000 series
products are best for RAID-0, 1 and 10, but I can't recommend
the 3Ware Escalade 9000 series for RAID-5 yet (although this
new Escalade 9550 looks very, very promising).

Bryan J. Smith                | Sent from Yahoo Mail
mailto:b.j.smith at ieee.org     |  (please excuse any
http://thebs413.blogspot.com/ |   missing headers)

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