On Mon, 24 Mar 2014 13:52:52 +0100 (CET) David Vasek <va...@fido.cz> wrote:
> On Sun, 23 Mar 2014, Robert wrote: > > > Hi, > > > > I have two external USB disks, 3TB and 4TB, in use like that. > > So far no problems, even after hard reboots (power outage). > > They are used for backups, and it's USB 2.0 - so I can't really say much > > about "intense writing"... > > Hi, > > thanks for your response. > > Did you tune the host filesystem in any way? What mount options do you use > for both the host filesystem and the one on the vnd image? > > By intensive writing I mean usage like "tar xzf ports.tar.gz" and such. It > is not "so much" intensive, but it possibly may cause problems > nonetheless. > > I already did some experiments with a 40 GB vnd image. I saw a little slow > tranfers over NFS (~ 6 MB/s and less when reading from the filesystem on a > vnd) and one complete lock up when the vnd was under read/write load. But > I was not able to reproduce the lock up later. > > Regards, > David > No tuning whatsoever. The powers that be said "thou shall not twist knobs" ;) Mount options for the file and VND: noatime, nodev, nosuid, softdep Performance: I get 6MB/sec, but I guess that's the USB2.0 limit. Those 8MB/sec over NFS is what I get as well (gbit LAN) for the internal disks - no matter if the server disk is softraid/crypto, or VND/crypto. On the client side all the nfsio start eating the CPU, and on the server side the nfsd. At some point the server/nfsd starts waiting for inode&biowait, and everything comes to a halt - until all the data is written to the disk. E.g., try to "dd if=/dev/zero of=/nfs/file bs=4k" and wait for a while (I guess until some cache fills up), or use ctrl-c. Good luck tuning NFS... Otherwise it works fine; as I said, I'm using it for backup with rsync (locally, not over NFS). Writing 1TB+ of files in one go was no problem. kind regards, Robert
