Re: [gentoo-user] LVM (Was: the best filesystem for server: XFS or JFS (or?))

["J. Roeleveld" <joost@antarean.org>]

On Thu, March 24, 2011 12:30 pm, Volker Armin Hemmann wrote:
> On Thursday 24 March 2011 08:49:52 J. Roeleveld wrote:
>> On Wed, March 23, 2011 5:43 pm, Volker Armin Hemmann wrote:
>> > md raid devices can do barriers. Don't know about lvm. But lvm is such
>> a
>> > can
>> > of worms I am surprised people still recommend it.
>>
>> What is wrong with LVM?
>> I've been using it successfully without any issues for years now.
>> It does what it says on the box.
>
> it is another layer that can go wrong. Why take the risk? There
> are enough cases of breakage after upgrades - and besides snapshots... is
> the
> amount of additional code running really worth it? Especially with bind
> mounting?

There are always things that can go wrong and I agree, adding additional
layers can increase the risk.
However, the benefits of easily and quickly changing the size of
partitions and creating snapshots for the use of backups are a big enough
benefit to off-set the risk.

Bind-mounting is ok, if you use a single filesystem for everything. I have
partitions that are filled with thousands of small files and partitions
filled with files are are, on average, at 1GB in size.
I haven't found a filesystem yet that successfully handles both of these
with identical performance.
When I first tested performance I found that a simple "ls" in a partition
would appear to just hang. This caused performance issues with my
IMAP-server.
I switched to a filesystem that better handles large amounts of small
files and performance increased significantly.

The way I do backups is that I stop the services, create snapshots and
then restart the services.
I then have plenty of time to backup the snapshot.
If I were to do this differently, I'd end up having a downtime for over an
hour just for a backup.
Now, it's barely a minute of downtime.

That, to me, is a very big bonus.

--
Joost