Re: RAID or no RAID

Danny Thomas wrote:

> is a journaled filesystem like lfs (http://www.hhhh.org/perseant/lfs.html)
> a good choice for squid?

It depends a lot on the filesystem, and I do not know the details of
lfs.

Squid without async-io may benefit from a journaled filesystem if the
journal speeds up metadata updates and provides a background task who
commits the changes to the disk structures.

For a Squid with async-io the journal as such will only slow things
down.

Some filesystems are slowed down a great deal by a journal. Others are
speeded up due to more intelligent update management and less need for
the application to wait for the update to take place.

> I asked Adrian Chadd about this and he said:
> My theory is that it will actually be nice to use if the storage code
> is modified just slightly to support FIFO object allocation

I sort of agree with Adrian there, but squid will quite likely have it's
own journaled object store suitable for RAID5 by then... Supporting FIFO
object allocation isn't a small task if one want's it done in a nice and
compatible manner.

> I'm looking at this as an interim measure till a squid fs appears -)

My iterim measure is to start Squid without cache drives while fsck is
running, and automatically mkfs the partition if fsck fails / needs
attention. Performance isn't a major problem here yet (have about 100%
performance margin, which ought to give us at least 6 to figure out how
to boost performance from the system).

--
Henrik Nordstrom
Squid hacker