Wednesday, March 30, 2011

Thank you Areca! 6Gbps 1880 support in illumos

A big thank you goes out to Areca.

Areca have provided the source code for their Solaris driver, including support for the newer 6G RAID adapters. As a result, I've integrated a (somewhat cleaned up) copy this code as an update to arcmsr(7d) in illumos, under generous open source licensing:

changeset:   13305:fb26af81b9b2
tag: tip
user: Garrett D'Amore
date: Fri Mar 25 22:14:56 2011 -0700
description:
834 need support for Areca 1880 6Gbps
Reviewed by: Dan McDonald <danmcd@nexenta.com>
Reviewed by: Albert Lee <trisk@nexenta.com>
Reviewed by: Richard Lowe <richlowe@richlowe.net>


This will make another HBA option available to folks. (Note these cards do support a JBOD mode, so you don't have to use hardware RAID -- indeed I would recommend that you don't when you have ZFS on the disks.

5 comments:

6thSense said...

Is your recommendation to NOT use hardware RAID based on any performance/reliability tests you've done or just general preference for using ZFS RAIDZ? If yes, maybe you can share the results of those tests? Thanks.

Garrett D'Amore said...

With ZFS, you have more control, and you can realize better performance without hardware RAID. I don't have quantitative measurements, but we've seen this enough times that it has become conventional wisdom.

There are other reasons to choose RAIDZ over hardware RAID, though.

1) RAIDZ has no write-hole, and thus no opportunity for silent data loss (hw RAID does unless you have a battery backup)

2) Management. RAIDZ lets the OS manage the configuration, including growing, replacing, etc. With HW RAID you are stuck using the tools the HW vendor provides, which are often suboptimal, especially for illumos or Solaris users. (And the code to manage that is often suboptimal.)

3) Portability. If your h/w RAID controller dies, you may not be able to recover your data from the drives. With RAIDZ, you can import those disks into any system that supports ZFS and keep right on plugging... no lock-in to the HBA or the HBA vendor.

4) Diagnosability/supportability. With ZFS, you have open source software and can look at what's happening there. And so can I. With hardware RAID, if bad things happen, you're at the mercy of the RAID vendor.

tm said...

really good news.

I had a lot of "fun" with areca raid cards (in pass through mode).

Do crash dumps now work really reliable (uadmin)

Thanks again for working on an alternative to the mpt fusion parts.

kebabbert said...

@6thSense,
ZFS can not repair data and can not guarantee data integrity if you use a hw raid card:
http://en.wikipedia.org/wiki/ZFS#Data_Integrity

davegeo said...

Areca also have the 1320 range of non-RAID controllers which would seem particularly suited to ZFS use and have a Solaris x86 driver...do these controllers work with Illumos at the moment(not in HCL explicitly)? Can the Areca Sol driver be used to replace the arcmsr driver? Anyone any experiences?