Re: RAID Questions

From: Jordyn A. Buchanan <>
Date: Wed, 15 Apr 1998 20:32:27 -0400

At 3:10 AM +0200 4/6/98, Henny Bekker wrote:
>Hi Dean,
>> We have been thinking about adding a RAID system to our FreeBSD/Squid
>> setup. Has anyone else added a RAID array to FreeBSD (2.2.6)? If so
>> what type of RAID are people using and what brands are supported under
>> FreeBSD?
>> Also does anyone know if a DLT is supported?
>I don't known of any RAID system for freeBSD while I'm using Squid on some
>IBM AIX systems.. We have achieved spectacular benefits when we switched
>from a JBOD (Just a Bunch Of Disks) to a striping disk-set. The average
>latency was reduced from 1 second to 0.2 seconds!! In the old situation
>(a non-striped journal file system) all disk activity was on one disk which
>was working at 100% and was causing for lots of waiting I/O CPU cycles..
>With diskstriping (RAID-0) all disks activity is equally divided among all
>disks.. [We are using a software disk-striping solution. I imagine a RAID-5
>crontroller (RAID-0 is even faster but does not have redundantcy) with
>write-through RAM of e.g. 8-MByte (or more) whould make the system even
>more faster!!]

RAID 0 should always be faster than RAID 5, since RAID 5 requires extra
writes for parity. Squid should balance between disks pretty well on its
own, although I haven't done a comparison of performance under a striped
disk system vs. squid making decisions on its own to see how this bears out
in reality.

FreeBSD allows you to implement RAID 0 using the ccd driver--man ccd and
check out the FreeBSD archives (at your favorite mirror) for
more information on this. You don't get the benefits of a sophisticated
caching controller this way, but it's straightforward to implement.

Some people outside the US may feel that the redundancy provided by RAID 5
outweighs the performance hit, but for an application like squid, I would
probably set the controller to implement RAID 0 even if it was RAID 5


|Jordyn A. Buchanan |
|Bestweb Corporation |
|Director of Technology +1.914.271.4500 |
Received on Wed Apr 15 1998 - 17:42:37 MDT

This archive was generated by hypermail pre-2.1.9 : Tue Dec 09 2003 - 16:39:42 MST