Re: [squid-users] Optimal cache_dir entries for 3 drives i.e. coss and aufs distribution

On 20.04.07 15:39, Mark Powell wrote:
> I have placed the 1st 2 drives into RAID1 for OS and everything except
> cache_dirs (/dev/amrd0). That leaves 3 drives for cache usage, which will
> not be RAID (/dev/amrd[123]). I'm wondering what is the best configuration
> for this. Currently I have 3 cache_dir entries:
>
> cache_dir coss /dev/amrd1 69881 max-size=16384 block-size=8192
> cache_dir aufs /2 62000 16 256
> cache_dir aufs /3 62000 16 256
>
> Would 2 coss cache_dirs perform better?
>
> cache_dir coss /dev/amrd1 69881 max-size=16384 block-size=8192
> cache_dir coss /dev/amrd2 69881 max-size=16384 block-size=8192
> cache_dir aufs /3 62000 16 256

I don't think so. I'm not sure you will have so much of so files <16Ki
that they will take up more space than files >16Ki.
I'd use the first possibility, with min-size set to, maybe just those 16Ki for
both aufs cache dirs.

> Also, what happens if drive for line 3 fails and I remove it's cache_dir
> entry. Does this mean objects over 16KB would never make it onto disk? And
> if so, is this something I need worry about?

Probably yes. however aren't they all RAID arrays?

> Total cache size is around the 180GB mark. That means about 1.8GB of RAM

I'd say you would have many small files, and the usage depends on the number
of files, not data used.

> will be used just storing the in-memory object index? I assume that won't
> be a problem with 4GB RAM to play with? Or should I reduce the amount
> cached on each drive?

if the clean size of disks/arrays is 69881KiB, I'd use ~55MiB for aufs.
Note that filesystems have usually bad performance if they are filled up too
much.

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