Re: Is TRIM/DISCARD going to be a performance problem?

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Mon, May 11, 2009 at 10:50:59AM -0400, Theodore Tso wrote:
> On Mon, May 11, 2009 at 10:29:51AM -0400, Ric Wheeler wrote:
> > The key is not at the FS layer - this is an issue for people who RAID 
> > these beasts together and want to actually check that the bits are what 
> > they should be (say doing a checksum validity check for a stripe).
> 
> Good point, yes I can see why they need that.  In that case, the
> storage device can't just silently truncate a TRIM request; it would
> have to expose to the OS its alignment requirements.  The risk though
> is that more they try push this compleixity into the OS, the higher
> the risk that the OS will simply decide not to take advantage of the
> functionality.  Of course, there is the question why anyone would want
> to build a software-raid device on top of a thin-provisioned hardware
> storage unit.  :-)

It's not a problem for people who use Thin Provisioning, it's a problem
for people who want to run RAID-5 on top of SSDs.  If you have a sector
whose reads are indeterminate, your parity for that stripe will always
be wrong.

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html

[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [Samba]     [Device Mapper]     [CEPH Development]
  Powered by Linux