Sparse or zero fill?

Relip

What do you guys use when creating a vm disk image: Sparse or zero fill?

I've been creating sparse file all the time (for personal use, of course), but I heard that sparse file can cause security issue. For example, someone who are using guest vm with sparse file can read a sector that isn't wiped out and extract password or something personal, which I think it is very low possibility though.

alex

who would waste their time by doing that?

Spirit

@alex said:
who would waste their time by doing that?

It happens. http://lowendtalk.com/discussion/9394/digital-ocean-private-data-leak

Rallias

In my honest opinion, sparse is better, so long as you keep TRIM enabled. However, it's unreliable. It requires you to have metadata to store the data properly, which introduces another point of failure.

Relip

@Rallias said:
In my honest opinion, sparse is better, so long as you keep TRIM enabled. However, it's unreliable. It requires you to have metadata to store the data properly, which introduces another point of failure.

TRIM is for SSDs, right? What about HDDs?

Rallias

@Relip said:
TRIM is for SSDs, right? What about HDDs?

Some mass-storage implementations will eliminate blocks from relevance with a TRIM command. LVM comes to mind with thin-provisioning. Beware of LVM thin-provisioning. I just lost a non-essential VM to it (my tech blog, I'm not going to re-create it until LXCNode comes online).

SSD trim is great. It will make it faster, and good SSD's will have enough power to write the metadata necessary.

I'm not sure HDD's will benefit from TRIM. If I were an HDD manufacturer, I would implement it if only to make sure bad blocks don't cause data loss.

concerto49

@Rallias @Relip HDD won't benefit from TRIM. TRIM is only needed since SSD saves time and increases endurance by writing out in large bundled blocks and doing deletes in batches also.

Rallias

@concerto49 said:
Rallias Relip HDD won't benefit from TRIM. TRIM is only needed since SSD saves time and increases endurance by writing out in large bundled blocks and doing deletes in batches also.

HDD won't benefit from TRIM considering SPEED alone. However, if they had a microprocessor on that HDD, they could make it MAJOR speedier and increase reliability. Gzip the data, TRIM so you got less data to consider, and be able to duplicate data on platter for reliability and prevent bad blocks from interfering with proper data access.

concerto49

@Rallias you're trending into something that Sandforce likely has a patent on. Maybe if you came up with that years ago.

Rallias

@concerto49 said:
Rallias you're trending into something that Sandforce likely has a patent on. Maybe if you came up with that years ago.

God... they shouldn't give patents out for a tower built out of linkin logs