On 01/11/06, Cyril Plisko <[EMAIL PROTECTED]> wrote:
On 11/1/06, Dick Davies <[EMAIL PROTECTED]> wrote:
> On 01/11/06, Dick Davies <[EMAIL PROTECTED]> wrote:
> > And we'll be able to use sparse zvols
> > for this too (can't think why we couldn't, but it'd be dead handy)?
>
> Thinking about this, we won't be able to (without some changes) -
> I think a target is zero-filled before going online
> (educated guess: it takes 5 minutes to 'online' a target,
> and it consumes virtually no space in the parent zvol if compression is on),
> so a sparse zvol would exhaust zpool space.
Looking at the code it doesn't seem like the backing store being zeroed.
In case of regular file a single sector (512 byte) of uninitialized data from
stack (bad practice ?) is written to the very end of the file. And in case
of character device it isn't written at all. zvol should fall into char device
category. See mgmt_create.c::setup_disk_backing()
Or did I miss something ?
I'm not the one to ask :)
I'm just saying what I've seen - it was SXCR b49, and a ZFS
filesystem, not a zvol as I said (seems iscsi targets are file backed
by default). Still took a few minutes to online a new target, so it was doing
something, but I don't know what.
If it's a non-issue that'd be great,
--
Rasputin :: Jack of All Trades - Master of Nuns
http://number9.hellooperator.net/
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