Topic: hardware raid

[exodus]

Has anyone used hardware raid in the system,  Are there any cards that are plug and play or will I need to install any drivers?

[gordonr]

Has anyone used hardware raid in the system,  Are there any cards that are plug and play or will I need to install any drivers?

If you need to install drivers, it's not "hardware" RAID. If you have a "hardware" RAID controller, you are able to set up your RAID volumes and then perform an install as if you only had one disk even though it is physically a mirrored pair. Good cards are indeed plug and play, but you'll need to set up your RAID volumes using some form of boot disk.

Avoid "hardware" RAID controllers which require drivers. The Linux software RAID frequently outperforms them in speed and robustness, and they cause significant pain with upgrades. "Hardware" RAID vendors have a bad habit of going out of business or losing interest in their drivers, leaving you with a real problem with some future kernel upgrade. I've even seen this from *big* vendors. If it needs a specific driver, avoid it.

IMO (and I am very much not alone), you are far better off with software RAID than a cheap "hardware" RAID controller.

http://linux.yyz.us/sata/faq-sata-raid.html

http://linuxmafia.com/faq/Hardware/sata.html

http://www.faqs.org/docs/Linux-HOWTO/ATA-RAID-HOWTO.html

http://www.ussg.iu.edu/hypermail/linux/kernel/0011.2/0914.html

Note that some cards allow you to load drivers for monitoring - that's a different issue. These drivers are not required for normal operations - they're nice to have, but not essential for system operation.

[smeghead]

I have several Compaq/HP Proliant systems in place using a variety of SmartArray controllers that all work great; if you get one that doesn't have a batery it will enable read caching only.  They all seem to do hot replace/rebuild (transparent to the OS) and some of the newer ones also do online expansion of the array (but not necessarily expansion of the OS partitions that sit on the array).

HTH

[dmajwool]

Has anyone used hardware raid in the system,  Are there any cards that are plug and play or will I need to install any drivers?

I use 3ware 8508 cards which support 8 x SATA drives.  They are plug and play in SME 6.01

I'm interested in SME7 software raid for large arrays, but SME6 software raid doesn't scale up beyond 2 disks.

HTH, David

[Reinhold]

I'm interested in SME7 software raid for large arrays, but SME6 software raid doesn't scale up beyond 2 disks.

I don't understand what you are trying to tell us here but
Software Raid 5 does work quite nicely on 4-12 IDE HD's in SME 6 and SME 7...  
and RAID6 does install and work automatically (nicely) if it detects more than the minimum number of HDs specified in SME 7bx.

Just use the Search Site function to find numerous places in this forum

Regards
Reinhold

[dmajwool]

I don't understand what you are trying to tell us here but...
Just use the Search Site function to find numerous places in this forum

Rinehold.
I do read the forums and the documentation, try to use the search functions, and help others where I can.  
Re: this topic, the following quote is from Section 5.2.1 of the SME6 user manual on this site. http://mirror.contribs.org/smeserver/contribs/bobk/SME_Manual/chpt-00.1-toc.html

SME Server supports a software implementation of RAID Level 1, known as disk mirroring. It does not support RAID Level 0 (disk striping), as that does not provide any protection of your data whatsoever. It does not support RAID Level 5 (disk striping with parity) because of the poor performance and reliability of software implementations of RAID5. If you are seeking RAID5 support, Contribs.org recommends you consider one of the many hardware implementations which will provide both protection and performance.

I didn't find any references to Software Raid 5 support on SME 6.  Can you suggest a search string?

I would certainly be interested to implement Raid 5 on SME6, I didn't appreciate it was supported. Apologies for my bad steer.

[Reinhold]

dmajwool,

No harm done - a little search for raid5 or raidtab is probably all you need to get going.

IN ADDITION to what gordonr already gave above, you may want to read
 The Software-RAID HOWTO by Jakob Østergaard (1st reading afaic)
and, since we are "hijacking" this thread  -sorry exodus- please also read the sata-faq as given above.

I would certainly be interested to implement Raid 5 on SME6,
I didn't appreciate it was supported.

Note: There is "only one software raid"-layer in linux which provides raid0 - raid5 (raid6 with kernel 2.6.x). If you get raid1 to work ... so will "the others".
(There are however several ways to set up and manipulate raid-arrays: raidtools on 6.0x and mdadm on 6.x (if installed) and on 7.x)

An older post of mine gave this info:

MAYBE I didn't make myself absolutely clear though as to the RAID5 capabilities of SME -sorry-
* RAID1 comes as an option in the setup procedure when more than 1 HD is detected ... basically you just "install 2nd HD, then - say: 'yes'"
* RAID5 (on SME) requires that you:
- install the raid5 HDs ... setup SME
- manually type a raidtab -file for your setup
- makefs that new setup
- complete fstab for your setup
(Note: a bootable raid5 setup on SME is different & a bit hardcore .-)

If you've got like 3 old HDs just play around a bit before getting serious .-)

... it still applies here. MHO: Go for a software raid - it's worth it!

Regards
Reinhold