Hi Bernd,<br><br>I am not quite clear how creating new OST on a loopback device would help:<br><br>Shall I create new OST on a loopback device formatting it with old index and label and then copy recovered objects to that OST and mount it to the filesystem?<br>
<br>I think I need to reformat old OST before mounting it as lustre type filesystem as although fsck recovered some objects (and I can access them mounting OST as ldiskfs) if you run tunefs.lustre on that OST device, tunefs.lustre complaints that it doesn't find any lustre filesystem.<br>
<br>As for the EAs I have created a backup of the recovered objects preserving EAs.<br><br>Best regards,<br><br>Wojciech<br><br><br> <br><br><div class="gmail_quote">On 26 October 2010 16:35, Bernd Schubert <span dir="ltr"><<a href="mailto:bernd.schubert@fastmail.fm">bernd.schubert@fastmail.fm</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">Hello Wojciech,<br>
<br>
I think both would work, but why don't just create a small OST with<br>
mkfs.lustre on a loopback device? And then copy over those files to your<br>
recovered filesystem.<br>
Hmm, well, e2fsck might not have fixed all issues and then a reformat indeed<br>
might be helpful.<br>
<br>
Also note: EAs on OST objects are a nice to have, but not absolutely required.<br>
<br>
Cheers,<br>
<font color="#888888">Bernd<br>
</font><div><div></div><div class="h5"><br>
<br>
On Tuesday, October 26, 2010, Wojciech Turek wrote:<br>
> Bernd, I would like to clarify if I understood you suggestion correctly:<br>
><br>
> 1) create a new OST but using old index and old label<br>
> 2) mount it as ldiskfs and copy recovered objects (using tar or rsync with<br>
> xattrs support) from the old OST to the new OST<br>
> 3) run --writeconf on MDT and OST of that filesystem<br>
> 4) mount MDT and all OSTs<br>
><br>
><br>
> I guess I could do it also that way:<br>
><br>
> 1) backup restored object using tar or rsync with xattrs support<br>
> 2) format old OST with old index and old label<br>
> 3) restore Objects from the backup<br>
><br>
> Do you think that would work?<br>
><br>
> Best regards,<br>
><br>
> Wojciech<br>
><br>
> On 22 October 2010 18:52, Bernd Schubert <<a href="mailto:bernd.schubert@fastmail.fm">bernd.schubert@fastmail.fm</a>> wrote:<br>
> > Hmm, I would probably format a small fake device on a ramdisk and copy<br>
> > files<br>
> > over, run tunefs --writeconf /mdt and then start everything (inlcuding<br>
> > all OSTs) again.<br>
> ><br>
> ><br>
> > Cheers,<br>
> ><br>
> > On Friday, October 22, 2010, Wojciech Turek wrote:<br>
> > > I have tried Bernd's suggestion and it seem to have worked, after<br>
> > > running e2fsck -D ll_recover_lost_found_objs didn't cause kernel panic<br>
> > > but moved<br>
> ><br>
> > a<br>
> ><br>
> > > number of objects to O directory. Problem is that I do not have<br>
> > > last_rcvd file so the OST has no index at the moment. What would be<br>
> > > the next step<br>
> ><br>
> > to<br>
> ><br>
> > > enable access to those files in the filesystem?<br>
> > ><br>
> > > Best regards,<br>
> > ><br>
> > > Wojciech<br>
> > ><br>
> > > On 22 October 2010 17:15, Andreas Dilger <<a href="mailto:andreas.dilger@oracle.com">andreas.dilger@oracle.com</a>><br>
> ><br>
> > wrote:<br>
> > > > On 2010-10-22, at 5:42, Bernd Schubert <<a href="mailto:bernd.schubert@fastmail.fm">bernd.schubert@fastmail.fm</a>><br>
> ><br>
> > wrote:<br>
> > > > > Hmm, e2fsck didn't catch that? rec_len is the length of a directory<br>
> > > ><br>
> > > > entry, so<br>
> > > ><br>
> > > > > after how many bytes the next entry follows.<br>
> > > ><br>
> > > > I agree that e2fsck should have caught that.<br>
> > > ><br>
> > > > > You can try to force e2fsck to do<br>
> > > > > something about that: e2fsck -D<br>
> > > ><br>
> > > > No, I would recommend against using -D at this point. That will cause<br>
> ><br>
> > it<br>
> ><br>
> > > > to re-write the directory contents, and given that the filesystem was<br>
> > > > previously corrupted I would prefer making as few changes as possible<br>
> > > > before the data is estranged.<br>
> > > ><br>
> > > > Wojciech,<br>
> > > > note that if you are able to mount the filesystem you could just copy<br>
> ><br>
> > all<br>
> ><br>
> > > > of the objects (with xattrs!) from lost+found on the bad filesystem,<br>
> > > > along with the last_rcvd file (if you can find it) into a new ldiskfs<br>
> > > > filesystem and then run ll_recover_lost_found_objs on that.<br>
> > > ><br>
> > > > > On Friday, October 22, 2010, Wojciech Turek wrote:<br>
> > > > >> Ok, removing and recreating the journal fixed that problem and I<br>
> > > > >> am able<br>
> > > ><br>
> > > > to<br>
> > > ><br>
> > > > >> mount device as ldiskfs filesystem. Now I hit another wall when<br>
> ><br>
> > trying<br>
> ><br>
> > > > to<br>
> > > ><br>
> > > > >> run ll_recover_lost_found_objs<br>
> > > > >> When I first time run ll_recover_lost_found_objs -d<br>
> > > > >> /mnt/ost/lost+found<br>
> > > ><br>
> > > > it<br>
> > > ><br>
> > > > >> only creates the O dir and exits. When I repeat this command again<br>
> > > ><br>
> > > > kernel<br>
> > > ><br>
> > > > >> panics. Any idea what could be the problem here?<br>
> > > > >><br>
> > > > >><br>
> > > > >> LDISKFS-fs error (device dm-4): ldiskfs_readdir: bad entry in<br>
> > > > >> directory #6831: rec_len is smaller than minimal - offset=0,<br>
> ><br>
> > inode=0,<br>
> ><br>
> > > > >> rec_len=0, name_len=0<br>
> > > > >> Aborting journal on device dm-4.<br>
> > > > >> Unable to handle kernel NULL pointer dereference at<br>
> > > > >> 0000000000000000<br>
> > > ><br>
> > > > RIP:<br>
> > > > >> [<ffffffff88033448>] :jbd:journal_commit_transaction+0xc5b/0x12db<br>
> > > > >> PGD 1a118d067 PUD 1ce7e7067 PMD 0<br>
> > > > >> Oops: 0002 [1] SMP<br>
> > > > >> last sysfs file: /class/infiniband_mad/umad0/port<br>
> > > > >> CPU 3<br>
> > > > >> Modules linked in: ldiskfs(U) crc16(U) autofs4(U) hidp(U) l2cap(U)<br>
> > > > >> bluetooth(U) rdma_ucm(U) rdma_cm(U) iw_cm(U) ib_addr(U)<br>
> > > > >> ib_ipoib(U) ipoib_helper(U) ib_cm(U) ipv6(U) xfrm_nalgo(U)<br>
> > > > >> crypto_api(U)<br>
> > > ><br>
> > > > ib_uverbs(U)<br>
> > > ><br>
> > > > >> ib_umad(U) mlx4_vnic(U) mlx4_vnic_helper(U) ib_sa(U) ib_mthca(U)<br>
> > > ><br>
> > > > mptctl(U)<br>
> > > ><br>
> > > > >> dm_mirror(U) video(U) backlight(U) sbs(U) power_meter(U) hwmon(U)<br>
> > > ><br>
> > > > i2c_ec(U)<br>
> > > ><br>
> > > > >> i2c_core(U) dell_wmi(U) wmi(U) button(U) battery(U) asus_acpi(U)<br>
> > > > >> acpi_memhotplug(U) ac(U) parport_pc(U) lp(U) parport(U) sr_mod(U)<br>
> > > ><br>
> > > > cdrom(U)<br>
> > > ><br>
> > > > >> mlx4_ib(U) ib_mad(U) ib_core(U) joydev(U) mlx4_core(U)<br>
> ><br>
> > usb_storage(U)<br>
> ><br>
> > > > >> pcspkr(U) shpchp(U) serio_raw(U) i5000_edac(U) edac_mc(U)<br>
> ><br>
> > dm_raid45(U)<br>
> ><br>
> > > > >> dm_message(U) dm_region_hash(U) dm_log(U) dm_mod(U)<br>
> > > > >> dm_mem_cache(U)<br>
> > > ><br>
> > > > nfs(U)<br>
> > > ><br>
> > > > >> lockd(U) fscache(U) nfs_acl(U) sunrpc(U) mptsas(U) mptscsih(U)<br>
> > > ><br>
> > > > mptbase(U)<br>
> > > ><br>
> > > > >> scsi_transport_sas(U) mppVhba(U) megaraid_sas(U) mppUpper(U) sg(U)<br>
> > > > >> sd_mod(U) scsi_mod(U) bnx2(U) ext3(U) jbd(U) uhci_hcd(U)<br>
> > > > >> ohci_hcd(U) ehci_hcd(U) Pid: 11360, comm: kjournald Tainted: G<br>
> > > > >> 2.6.18-194.3.1.el5_lustre.1.8.4 #1<br>
> > > > >> RIP: 0010:[<ffffffff88033448>] [<ffffffff88033448>]<br>
> > > > >><br>
> > > > >> :jbd:journal_commit_transaction+0xc5b/0x12db<br>
> > > > >><br>
> > > > >> RSP: 0018:ffff8101c6481d90 EFLAGS: 00010246<br>
> > > > >> RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00000000ffffffff<br>
> > > > >> RDX: 0000000000000000 RSI: ffff8101e9dab0c0 RDI: ffff81022fa46000<br>
> > > > >> RBP: ffff81022fa46000 R08: ffff81022fa46068 R09: 0000000000000000<br>
> > > > >> R10: ffff810105925b20 R11: 00000000fffffffa R12: 0000000000000000<br>
> > > > >> R13: 0000000000000000 R14: ffff8101e9dab0c0 R15: 0000000000000000<br>
> > > > >> FS: 0000000000000000(0000) GS:ffff810107b9a4c0(0000)<br>
> > > > >> knlGS:0000000000000000 CS: 0010 DS: 0018 ES: 0018 CR0:<br>
> > > > >> 000000008005003b CR2: 0000000000000000 CR3: 00000001eaffb000 CR4:<br>
> > > > >> 00000000000006e0 Process kjournald (pid: 11360, threadinfo<br>
> > > > >> ffff8101c6480000, task ffff81021c14c0c0)<br>
> > > > >> Stack: ffff8101a61b9000 000000002b8263c0 ffffffff00000000<br>
> > > ><br>
> > > > 0000000000000000<br>
> > > ><br>
> > > > >> 0000113b00000001 0000000000000013 0000000000000000<br>
> > > > >> 0000000000000111 0000000000000000 0000000000000000<br>
> > > > >> 0000000001282dd7 00000000000020dd Call Trace:<br>
> > > > >> [<ffffffff8003da91>] lock_timer_base+0x1b/0x3c<br>
> > > > >> [<ffffffff8004b347>] try_to_del_timer_sync+0x7f/0x88<br>
> > > > >> [<ffffffff88037386>] :jbd:kjournald+0xc1/0x213<br>
> > > > >> [<ffffffff800a0ab2>] autoremove_wake_function+0x0/0x2e<br>
> > > > >> [<ffffffff800a089a>] keventd_create_kthread+0x0/0xc4<br>
> > > > >> [<ffffffff880372c5>] :jbd:kjournald+0x0/0x213<br>
> > > > >> [<ffffffff800a089a>] keventd_create_kthread+0x0/0xc4<br>
> > > > >> [<ffffffff80032890>] kthread+0xfe/0x132<br>
> > > > >> [<ffffffff8005dfb1>] child_rip+0xa/0x11<br>
> > > > >> [<ffffffff800a089a>] keventd_create_kthread+0x0/0xc4<br>
> > > > >> [<ffffffff8014bcf4>] deadline_queue_empty+0x0/0x23<br>
> > > > >> [<ffffffff80032792>] kthread+0x0/0x132<br>
> > > > >> [<ffffffff8005dfa7>] child_rip+0x0/0x11<br>
> > > > >><br>
> > > > >><br>
> > > > >> Code: f0 0f ba 33 01 e8 42 fc 02 f8 8b 03 a8 04 75 07 8b 43 58 85<br>
> > > > >> RIP [<ffffffff88033448>]<br>
> > :<br>
> > :jbd:journal_commit_transaction+0xc5b/0x12db<br>
> > :<br>
> > > > >> RSP <ffff8101c6481d90><br>
> > > > >> CR2: 0000000000000000<br>
> > > > >> <0>Kernel panic - not syncing: Fatal exception<br>
> > > > >><br>
> > > > >> On 22 October 2010 03:09, Andreas Dilger<br>
> > > > >> <<a href="mailto:andreas.dilger@oracle.com">andreas.dilger@oracle.com</a><br>
> > > ><br>
> > > > wrote:<br>
> > > > >>> On 2010-10-21, at 18:44, Wojciech Turek <<a href="mailto:wjt27@cam.ac.uk">wjt27@cam.ac.uk</a>> wrote:<br>
> > > > >>><br>
> > > > >>> fsck has finished and does not find any more errors to correct.<br>
> > > > >>> However when I try to mount the device as ldiskfs kernel panics<br>
> ><br>
> > with<br>
> ><br>
> > > > >>> following message:<br>
> > > > >>><br>
> > > > >>> Assertion failure in cleanup_journal_tail() at<br>
> > > > >>> fs/jbd/checkpoint.c:459: "blocknr != 0"<br>
> > > > >>><br>
> > > > >>><br>
> > > > >>> Hmm, not sure, maybe your journal is broken? You can delete it<br>
> ><br>
> > with<br>
> ><br>
> > > > >>> "tune2fs -O ^has_journal" (maybe after running e2fsck again to<br>
> ><br>
> > clear<br>
> ><br>
> > > > the<br>
> > > ><br>
> > > > >>> journal), then re-create it with "tune2fs -j".<br>
> > > > >>><br>
> > > > >>> ----------- [cut here ] --------- [please bite here ] ---------<br>
> > > > >>> Kernel BUG at fs/jbd/checkpoint.c:459<br>
> > > > >>> invalid opcode: 0000 [1] SMP<br>
> > > > >>> last sysfs file: /class/infiniband_mad/umad0/<br>
> > > > >>> port<br>
> > > > >>> CPU 2<br>
> > > > >>> Modules linked in: obdfilter(U) fsfilt_ldiskfs(U) ost(U) mgc(U)<br>
> > > > >>> ldiskfs(U) crc16(U) lustre(U) lov(U) mdc(U) lquota(U) osc(U)<br>
> > > ><br>
> > > > ksocklnd(U)<br>
> > > ><br>
> > > > >>> ko2iblnd(U) ptlrpc(U) obdclass(U) lnet(U) lvfs(U) libcfs(U)<br>
> > > > >>> autofs4(U) hidp(U) l2cap(U) bluetooth(U) rdma_ucm(U) rdma_cm(U)<br>
> > > > >>> iw_cm(U)<br>
> > > ><br>
> > > > ib_addr(U)<br>
> > > ><br>
> > > > >>> ib_ipoib(U) ipoib_helper(U) ib_cm(U) ipv6(U) xfrm_nalgo(U)<br>
> > > ><br>
> > > > crypto_api(U)<br>
> > > ><br>
> > > > >>> ib_uverbs(U) ib_umad(U) mlx4_vnic(U) mlx4_vnic_helper(U) ib_sa(U)<br>
> > > > >>> ib_mthca(U) mptctl(U) dm_mirror(U) video(U) backlight(U) sbs(U)<br>
> > > > >>> power_meter(U) hwmon(U) i2c_ec(U) i2c_core(U) dell_wmi(U) wmi(U)<br>
> > > > >>> button(U) battery(U) asus_acpi(U) acpi_memhotplug(U) ac(U)<br>
> > > ><br>
> > > > parport_pc(U)<br>
> > > ><br>
> > > > >>> lp(U) parport(U) sr_mod(U) cdrom(U) mlx4_ib(U) ib_mad(U)<br>
> > > > >>> ib_core(U) joydev(U) mlx4_core(U) usb_storage(U) shpchp(U)<br>
> > > > >>> i5000_edac(U)<br>
> > > ><br>
> > > > edac_mc(U)<br>
> > > ><br>
> > > > >>> serio_raw(U) pcspkr(U) dm_raid45(U) dm_message(U)<br>
> > > > >>> dm_region_hash(U) dm_log(U) dm_mod(U) dm_mem_cache(U) nfs(U)<br>
> > > > >>> lockd(U) fscache(U) nfs_acl(U) sunrpc(U) mptsas(U) mptscsih(U)<br>
> > > > >>> mptbase(U)<br>
> > > > >>> scsi_transport_sas(U) mppVhba(U) megaraid_sas(U) mppUpper(U)<br>
> > > > >>> sg(U) sd_mod(U) scsi_mod(U) bnx2(U) ext3(U) jbd(U) uhci_hcd(U)<br>
> ><br>
> > ohci_hcd(U)<br>
> ><br>
> > > > >>> ehci_hcd(U) Pid: 13891, comm: mount Tainted: G<br>
> > > > >>> 2.6.18-194.3.1.el5_lustre.1.8.4 #1 RIP: 0010:[<ffffffff88034a95>]<br>
> > > > >>> [<ffffffff88034a95>]<br>
> > > > >>><br>
> > > > >>> :jbd:cleanup_journal_tail+0x9d/0x118<br>
> > > > >>><br>
> > > > >>> RSP: 0018:ffff81016f00da68 EFLAGS: 00010286<br>
> > > > >>> RAX: 000000000000005a RBX: ffff81012ca12c00 RCX: ffffffff80311da8<br>
> > > > >>> RDX: ffffffff80311da8 RSI: 0000000000000000 RDI: ffffffff80311da0<br>
> > > > >>> RBP: 0000000000000000 R08: ffffffff80311da8 R09: 0000000000000001<br>
> > > > >>> R10: 0000000000000000 R11: 0000000000000080 R12: 0000000000000002<br>
> > > > >>> R13: ffff81012ca12d4c R14: ffff81012ca12c24 R15: ffff81017a8d7400<br>
> > > > >>> FS: 00002abd7cef1f70(0000) GS:ffff810107b9acc0(0000)<br>
> > > > >>> knlGS:0000000000000000<br>
> > > > >>> CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b<br>
> > > > >>> CR2: 000000000042b000 CR3: 000000012813f000 CR4: 00000000000006e0<br>
> > > > >>> Process mount (pid: 13891, threadinfo ffff81016f00c000, task<br>
> > > > >>> ffff81022e1b7820)<br>
> > > > >>> Stack: 0000000000000000 ffff81012ca12c00 ffff81017a8d7400<br>
> > > > >>> ffffffff88037690<br>
> > > > >>><br>
> > > > >>> ffff81012ca12c00 ffff8102034ff000 ffff81017a8d7400<br>
> > > > >>> 0000000000000000 ffff8102034ff000 ffffffff88a9be56<br>
> > > > >>> 0000000001000000 ffff8101bf788000<br>
> > > > >>><br>
> > > > >>> Call Trace:<br>
> > > > >>> [<ffffffff88037690>] :jbd:journal_flush+0xbe/0x248<br>
> > > > >>> [<ffffffff88a9be56>]<br>
> > > > >>><br>
> > > > >>> :ldiskfs:ldiskfs_mark_recovery_complete+0x36/0x90<br>
> > > > >>><br>
> > > > >>> [<ffffffff88aa02e0>] :ldiskfs:ldiskfs_fill_super+0x1790/0x1950<br>
> > > > >>> [<ffffffff800eccd2>] get_filesystem+0x12/0x3b<br>
> > > > >>> [<ffffffff800e343e>] test_bdev_super+0x0/0xd<br>
> > > > >>> [<ffffffff88a9eb50>] :ldiskfs:ldiskfs_fill_super+0x0/0x1950<br>
> > > > >>> [<ffffffff800e43fd>] get_sb_bdev+0x10a/0x16c<br>
> > > > >>> [<ffffffff800e3d9a>] vfs_kern_mount+0x93/0x11a<br>
> > > > >>> [<ffffffff800e3e63>] do_kern_mount+0x36/0x4d<br>
> > > > >>> [<ffffffff800ee601>] do_mount+0x6a9/0x719<br>
> > > > >>> [<ffffffff800090d2>] __handle_mm_fault+0x96f/0xfaa<br>
> > > > >>> [<ffffffff8002c9e0>] mntput_no_expire+0x19/0x89<br>
> > > > >>> [<ffffffff8000a72a>] __link_path_walk+0xf1e/0xf42<br>
> > > > >>> [<ffffffff800220ce>] __up_read+0x19/0x7f<br>
> > > > >>> [<ffffffff80066b88>] do_page_fault+0x4fe/0x874<br>
> > > > >>> [<ffffffff8002c9e0>] mntput_no_expire+0x19/0x89<br>
> > > > >>> [<ffffffff8000ea45>] link_path_walk+0xa6/0xb2<br>
> > > > >>> [<ffffffff800cc329>] zone_statistics+0x3e/0x6d<br>
> > > > >>> [<ffffffff8000f2cf>] __alloc_pages+0x78/0x308<br>
> > > > >>> [<ffffffff8004c68e>] sys_mount+0x8a/0xcd<br>
> > > > >>> [<ffffffff8005d28d>] tracesys+0xd5/0xe0<br>
> > > > >>><br>
> > > > >>> Code: 0f 0b 68 3a 94 03 88 c2 cb 01 44 39 a3 58 01 00 00 75 0e c7<br>
> > > > >>> RIP [<ffffffff88034a95>] :jbd:cleanup_journal_tail+0x9d/0x118<br>
> > > > >>><br>
> > > > >>> RSP <ffff81016f00da68><br>
> > > > >>> <0>Kernel panic - not syncing: Fatal exception<br>
> > > > >>><br>
> > > > >>> Any idea how to fix this?<br>
> > > > >>><br>
> > > > >>> Many thanks<br>
> > > > >>><br>
> > > > >>> Wojciech<br>
> > > > >>><br>
> > > > >>><br>
> > > > >>> On 21 October 2010 17:54, Wojciech Turek < <<a href="mailto:wjt27@cam.ac.uk">wjt27@cam.ac.uk</a>><br>
> > > > >>><br>
> > > > >>> <a href="mailto:wjt27@cam.ac.uk">wjt27@cam.ac.uk</a>> wrote:<br>
> > > > >>>> Thanks Ken, that worked.<br>
> > > > >>>><br>
> > > > >>>><br>
> > > > >>>> On 21 October 2010 17:39, Ken Hornstein <<br>
> > > > >>>> <<a href="mailto:kenh@cmf.nrl.navy.mil">kenh@cmf.nrl.navy.mil</a>><br>
> > > > >>>><br>
> > > > >>>> <a href="mailto:kenh@cmf.nrl.navy.mil">kenh@cmf.nrl.navy.mil</a>> wrote:<br>
> > > > >>>>>> Now I have another problem. After last segfault I can not<br>
> ><br>
> > restart<br>
> ><br>
> > > > the<br>
> > > ><br>
> > > > >>>>> fsck<br>
> > > > >>>>><br>
> > > > >>>>>> due to MMP.<br>
> > > > >>>>>> [...]<br>
> > > > >>>>>> Also when I try to access filesystem via debugfs it fails:<br>
> > > > >>>>>><br>
> > > > >>>>>> debugfs -c -R 'ls' /dev/scratch2_ost16vg/ost16lv<br>
> > > > >>>>>> debugfs 1.41.10.sun2 (24-Feb-2010)<br>
> > > > >>>>>> /dev/scratch2_ost16vg/ost16lv: MMP: fsck being run while<br>
> > > > >>>>>> opening<br>
> > > > >>>>><br>
> > > > >>>>> filesystem<br>
> > > > >>>>><br>
> > > > >>>>>> ls: Filesystem not open<br>
> > > > >>>>>><br>
> > > > >>>>>> Is there a way to clear teh MMP flag so it allows fsck to run?<br>
> > > > >>>>><br>
> > > > >>>>> You want tune2fs -f -E clear-mmp<br>
> > > > >>>>><br>
> > > > >>>>> --Ken<br>
<br>
</div></div></blockquote></div><br><br clear="all"><br>-- <br>Wojciech Turek<br><br>Senior System Architect<br><br>High Performance Computing Service<br>University of Cambridge<br>Email: <a href="mailto:wjt27@cam.ac.uk" target="_blank">wjt27@cam.ac.uk</a><br>
Tel: (+)44 1223 763517 <br>