[lkml]   [2007]   [Apr]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
On Fri, 06 Apr 2007 19:47:36 PDT, said:
> On Fri, 6 Apr 2007 11:21:19 -0400, "Jan Harkes" <>

> > With compression there is a pretty high probability that one corrupted
> > byte or disk block will result in loss of a considerably larger amount
> > of data.
> Bad blocks are NOT dealt with by the filesystem,... so your comment is
> irrelevant, or just plain wrong.
> If your filesystem is writing to bad blocks, then throw away your
> operating system.

You know... occasionally, blocks go bad *after* you write to them. If
you have an uncompressed filesystem, it's often possible to recover most
of the file , and just have a few 512-byte blocks of zeros, simply by
doing something like 'dd if=bad.file of=bad.file bs=512 conv=noerror'
or careful applications of 'skip=N'. If it's compressed, you usually
can't recover the rest of a compression group if a previous block is lost.

(And for those who talk about backups - yes, taking backups is good.
However, it's the rare laptop or desktop machine that can afford the
luxury of RAID disks, and backups usually happen once a night, if that
often. This means that if you've been working hard on something important
all day, and the disk blows chunks at 4:30PM, you *will* be suddenly very
concerned over exactly how much you can recover off the failing drive....

And yes, I'd *love* to have all my users connected to nice SAN systems that do
snapshotting and remote replication to DR sites and all that - but have you
ever *priced* a petabyte of SAN storage, the NAS gateways to serve it to users,
and upgrading several tens of thousands of network ports to Gig-E? Hint -
US$1M would get us through a pilot, and probably $5M and up to *start*
deployment. Anybody wanna buy us an EMC DMX-3? :)

[unhandled content-type:application/pgp-signature]
 \ /
  Last update: 2007-04-07 19:43    [W:0.160 / U:2.140 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site