Areca Weirdness

[Fabian Wenk]

Hello Lawrence

Lawrence Farr wrote:

> Thanks for taking the time to write such a detailed reply!

You're welcome. Probably it will also help others when building 
large file systems.

> I created a 2Tb volume within the raid set and booted off that

Ah, ok. Yes, the Areca controller have some interesting new ideas 
how you can use the disks in a RAID. In the first place, it looked 
strange to me, but then I realised how flexible it could be.

Building a raidset without giving them any RAID level and then 
define the RAID level for the volume (the "disk" for the OS) which 
is build on the raidset. Even change (upgrade) a volume from eg. 
RAID-5 to RAID-6 is possible. If there are still empty ports on a 
controller, a raidset can be expanded with adding another disk. 
Expanding of a volume also is possible, but the OS then needs to 
grow the filesystem too.

About the 2 TB disk size limit, on servers I always use the "DD" 
mode to build the partition, eg. without the DOS compatible MBR 
and boot loader. I guess then also a boot partition larger as 2 TB 
should be possible, but I did not try. In the servers with large 
filesystem I always have a separate RAID controller with only 2 
small disks (80 GB) mirrored for the system. It is nice to have a 
system running at multiuser when in need do debug problems with 
the large filesystem / RAID.

I have one server with a dual channel SCSI ICP RAID controller 
with 16x 140 GB disks (RAID-5 with 1 hot spare). The disk in 
FreeBSD is reported as "da0: 1963350MB (4020940980 512 byte 
sectors: 255H 63S/T 250292C)". On the disk I have one slice ("DD" 
mode) with 6 GB /, 4 GB swap and 2x 950 GB data partitions, which 
works just fine, but maybe this is because its below 1 and 2 TB.

> without issue in the end. On Linux and FreeBSD I had to use GPT
> support for the larger partitions. Coincidentally, the culprit

I did not know (or remember) about GPT, after some googling I 
found "Large data storage in FreeBSD" [1], but when I look a the 
tables, it seems that this page has not been updated anymore.

   [1] http://www2.ch.freebsd.org/projects/bigdisk/index.html

When we built the first large (4.5 TB) filesystem in February 2004 
with FreeBSD 5.2 we run into several problems which needed fine 
tuning (eg. reducing the number of inodes). But as of today, I 
have a 8TB filesytem running on FreeBSD/i386 6.1-RELEASE with 
quota (only to report, not to enforce) so far without problems. We 
still reduce the number of inodes, as the defaults are to much.

> of the mystery crashes that I was having may have been a dodgy
> power supply (it went off with an impressive bang yesterday). 

We also had strange problems with regular PCs. Was surprised that 
a PSU could be half dead, but you always can learn something new. ;)

> It had been fine on i386 booting directly from the Areca for a
> few weeks now tho.

Should be a the normal thing in life, but experience tells an 
other story.


bye
Fabian