RE: [squid-users] To RAID or not to RAID...

How does this react when a drive dies and a cached object that is requested
was on the dead drive?

-----Original Message-----
From: Joe Cooper [mailto:joe@swelltech.com]
Sent: Monday, 3 June 2002 2:49 PM
To: Phil Oester
Cc: squid-users@squid-cache.org
Subject: Re: [squid-users] To RAID or not to RAID...

Oh, goodness...Wrongness on so many levels! ;-)

Squid produces very nearly the worst-case scenario for RAID 5. Squid
distributes its workload evenly across disks without breaking objects
into pieces. Squid does a better job choosing a disk than your RAID
will. Let it. And, you don't lose all of the cache store if one drive
dies.

270GB of cache storage will require roughly 2.7GB of RAM just for the
object store. On a machine with only 1GB of RAM, I usually use about
20-36GB of cache_dir space, and 36GB is pushing it if I'm looking for
really high performance from the machine. Our standard machine that
ships with 1GB of RAM is configured to use 24GB of space for cache_dir,
and it performs wonderfully.

Both issues have been discussed a few times in the archives, which may
be worth digging up. The amount of memory required for a given Squid
installation is discussed at length in the Squid FAQ, including the
information about sizing memory based on amount of cache storage in use.
  RAID is probably also discussed in the FAQ. A search (there is a
search button on the frontpage) of the Squid site will turn up
interesting things, I'm sure.

Maybe you can find another use for all those 72GB disks, eh?

Phil Oester wrote:
> I've got a dual 1ghz, 1gb system with 5x72gb drives, and am wondering
> what the best configuration would be for the drives/cache.
>
> Since it has a hardware RAID controller, my initial inclination would be
> to go RAID 5 across all 5 drives (no hot spare), and after the OS, I'd
> be left with ~270gb for the cache partition. But I've been reading a
> few old posts and some people have suggested avoiding RAID.
>
> Another possibility was to put Linux on 1 drive, then use a RAID 0
> stripe across the other 4 drives for speed. Granted, if I blow any
> single drive in the box, I'm hosed - but I'll have 3 total boxes in a
> load balanced configuration.
>
> Any thoughts?
>
> Also - given the above 1gb RAM configuration, what is the largest cache
> size you would recommend? Should I use the available 270gb, or should I
> cut it off at some limit? I'll be using AUFS on Linux 2.4.
>
> - Phil
>

-- 
Joe Cooper <joe@swelltech.com>
Web caching appliances and support.
http://www.swelltech.com