CentOS - Aug 2007 - OT: Suggestions for RAID HW for 2 SATA drives in DellPowerEdge SC

On 29 August 2007, "Ross S. W. Walker" <rwalker at
medallion.com> wrote:
> Message: 39
<snip>
> I wouldn't worry too much about the OS HD configuration, you are
> always going to want RAID1 for the OS, whether software or hardware.
> 
> Reason I say not to worry too much about the OS HD config is because
> you are almost certainly going to put the application or user data
> on a separate array, so the OS HD is basically used for loading
> binaries.
Ross: Thank you! I also read your reply to Israel in Cuba, which may be
applicable for me.

About 10 seconds after I started this thread, I remembered a long discussion
about
RAID, SATA, etc., 2 or 3 months ago. I think that Feizhou (?) strongly
recommended
going with Software RAID in CentOS. I will search for that and do a lot of
reading. RAID 1 for mirroring is what I want. Lanny

On 30 August 2007, "Alain Spineux" <aspineux at gmail.com>
wrote:
> Message: 50
<snip>
> RAID 1 is mirroring (data are stored on both diks), RAID 0 is striping
(data
> are split between both disk).
> If one disk fail, You will loose your data in RAID 0, not in RAID 1.
> 
> You can change this setting yourself later using the BIOS menu or the DELL
> CD.
> 
> I recommend RAID 1 for safety
> 
> Regards
> 
> PS: RAID 1 don't dispense you to regularly check if both disk are
healthy
> and how to replace a defect one without losing valuable data saved on the
> other.
> 
Alain: Thank you. RAID 1 it is. Also, I will do burn in tests, on the RAM and
drives, before I begin configuring the box. And, learning how to remove/replace
a defective drive is something I should do. Lanny

> About 10 seconds after I started this thread, I remembered a long
discussion about
> RAID, SATA, etc., 2 or 3 months ago. I think that Feizhou (?) strongly
recommended
> going with Software RAID in CentOS. I will search for that and do a lot of
> reading. RAID 1 for mirroring is what I want. Lanny
Whoa there!

Hardware raid + battery backed up memory cache in raid 1,10 mode is hard 
to beat with software raid and hardware raid offers data integrity 
guarantee beyond software raid.

If you were planning a huge array especially a raid5 array, then 
software raid may be better. Hardware RAID cards all come with memory 
caches now so their throughput is no longer limited.

Another route you can go is getting a PCI/PCIe/PCI-X BBU RAM/NVRAM card 
to put an external journal on to speed up fsync performance for 
filesystems like ext3 over software raid since these cards can go beyond 
1GB of memory unlike hardware raid cards that usually max out at 256MB.

Software RAID is also good if you need to be able to transfer the disks 
to another box that does not have a hardware raid controller or the same 
controller.

Weigh these in your decision. :-)

On 31 August 2007, Feizhou <feizhou at graffiti.net>
wrote:
> Message: 77
<snip>
> Whoa there!
> 
> Hardware raid + battery backed up memory cache in raid 1,10 mode is
> hard to beat with software raid and hardware raid offers data
> integrity guarantee beyond software raid.
> 
> If you were planning a huge array especially a raid5 array, then 
> software raid may be better. Hardware RAID cards all come with memory 
> caches now so their throughput is no longer limited.
> 
> Another route you can go is getting a PCI/PCIe/PCI-X BBU RAM/NVRAM
> card to put an external journal on to speed up fsync performance for 
> filesystems like ext3 over software raid since these cards can go
> beyond 1GB of memory unlike hardware raid cards that usually max out
> at 256MB.
> 
> Software RAID is also good if you need to be able to transfer the
> disks to another box that does not have a hardware raid controller or
> the same controller.
> 
Feizhou: THANK YOU! What you wrote is *extremely* helpful (and
educational) for me! MUCH appreciated! Lanny

On 31 August 2007 , Feizhou <feizhou at graffiti.net>
wrote:
> Message: 11
<snip>
> > Besides I do not believe the PERC 5IR has BBU cache, that
> > controller is really only meant as a simple RAID1 controller for
> > the OS.
I'll try to find out.
> Dell certainly has a BBU cache option, not sure if OP's Poweredge box 
> has that option.
It's a very low end box. Starting with the lowest price server they have,
with upgrades. I'll try to find the specs for it!