Archive for August, 2010

Mobile data coverage

Monday, August 23rd, 2010

I should point out right at the start of this that I rarely use a mobile phone (I have one supplied by my employer for work but it is a very basic phone and I keep it turned off most of the time, using it only to phone back to the office — typically when abroad.  I don’t think it can be used for internet access or anything fancy).  I don’t have a personal mobile phone.

When I bought my iPad i got the 3G model together with a micro SIM for O2 in the UK.   The thinking was that the O2 data connection can be set up on the iPad itself without having to make phone calls or enter in to contracts, and the cost is quite reasonable.  There is a £2 for 24 hours (limited to 500MB bandwidth) option and other more expensive options for 30 day periods with either 1GB or 3GB allowances for the 30 days.   They all come with free wi-fi for the corresponding period at O2 hotspots.  Given the often very expensive charge for a Wi-Fi connection in many hotels I thought it would be useful (at least in the UK when travelling).  I have used it a few times now at airports where the Wi-Fi is expensive (and where the frequent flyer lounge doesn’t offer free Wi-Fi) and it has worked well.

Recently I tried using it while travelling in a taxi on the M42 and M5 south.  This was not such a pleasant experience.   Given all of the hype around the connectedness of mobile phones and the like I was somewhat surprised that it was practically impossible to do anything useful on the iPad while travelling in the back of a taxi — and this wasn’t because of any rough ride. Actually getting a connection to O2 to buy access took probably 10 miles of travel.    For most of the journey there was very little data connectivity and when there was it was mostly EDGE rather than 3G.  In fact the coverage basically seemed to extend for a short distance around motorway junctions with virtually nothing in between.   Certainly it would not be much use for using any GPS application that required a data connection.   (Although provided you don’t want directions but just use the iPad as a replace for a road atlas MotionX GPS HD is very good and doesn’t require a data connection provided you download the OpenStreetMap tiles ahead of time.)  I don’t know whether the reception is any better on the UK railways; perhaps I’ll find out soon.


Updated post about using Topaz filters for high ISO photography

Monday, August 16th, 2010

A few weeks ago Topaz Labs announced an update to their Denoise filter to Denoise 5.  Having installed this I thought I should reprocess the example in a previous post to see how it worked for me.  I think the end result is pretty good given that the original photograph was a couple of stops underexposed at the highest ISO setting of my rather old Canon 300D (the original Digital Rebel in the US).

Time Machine fix

Saturday, August 7th, 2010

When I wrote the last post about back up strategy, I had intended to write about a small Time Machine problem I had and its solution.  Unfortunately the preamble became an entire post in its own right.

I recently had a situation where TIme Machine got stuck.  It was apparently preparing a back up but despite trying to stop it and to unmount the volume in various ways, I could not get it to stop.   One thing I didn’t try, which might have worked, was to logout.

However a search on the internet found this, although the key part of this hint is actually in the comments as for me, it was stopping and restarting the Spotlight indexing service that allowed Time Machine to make progress.

sudo service stop
sudo service start

Backups on Mac OS X

Saturday, August 7th, 2010

I tend to be quite paranoid about backing up data.   I think many people fail to realise how much “difficult to replace” data may be sitting on their hard drives: digital photographs (not like the old days when one had shoe boxes of prints and/or negatives), financial information, research notes (not just academic but also for hobbies and so on), e-mails (if not stored on IMAP servers — and even if they are I always like to have a back up), and so on.  There’s also a saying that if data is not stored in 3 places, then its not stored at all.

Apple’s Time Machine has been a tremendous boon to make back up easier.  The fact that it is mostly set it and forget it means that once one has bought an external drive that is either permanently connected for a desk top machine or at least regularly connected to a laptop then one is going to be able to recover files with ease (and not just the most recent version, but depending on the space on the Time Machine hard drive, possibly many months or even years).  I use Time Machine with all of my Macs.

The disadvantage with Time Machine is that you cannot boot from a Time Machine disk so that if a hard drive goes bad in your computer you need to reinstall the OS on a new drive and then use the Migration Assistant to recover from the Time Machine backup.  Another approach to backup is to make a clone of a hard drive.  Several applications support this, the best known being SuperDuper and Carbon Copy Cloner.  SuperDuper is free for simple use but the incremental back up features are enabled on payment.  Carbon Copy Cloner is donation ware.   I’ve used SuperDuper for some years now, although I did use Carbon Copy Cloner for a period when CCC had been upgraded for Leopard, but SuperDuper was lagging behind.  The great thing about both of these applications is that they can clone the hard drive so that the clone is bootable.   This is a great fallback if a hard drive fails when you really need the machine.   While running off an external hard drive is slow, it can be a life saver.   I’ve also used this when upgrading the operating system and deciding that I need to revert to the previous version.  In fact I always due a clone before installing software updates just in case there is a problem.  These are also essential tools if one is upgrading one’s system disk.

For my MacBook I have a TIme Machine backup and typically two cloned back-ups — one is on a desktop external hard drive and the other on a portable hard drive.

Of course, if all the hard drives that are used for back up are in the same place, then fire or a break-in may lead to the loss of all of them.  For this reason, one should keep a second copy of a backup elsewhere.  Many people keep a second cloned hard drive at their office (or at a relative’s house) and each week will swap over the drives.

The other option for offsite back up is to use one of the cloud back up services.   The big disadvantage of cloud back up is that it will take forever to do the initial backup given that most of us are on assymetric internet connections so our upload speed may only be 384Kb/s even if we have 8Mb/s download.  Also as some ISPs are imposing bandwidth restrictions and/or charging for bandwidth this can make online back up less practical.   I use Jungle Disk which effectively is a front-end to using Amazon S3 (which I use) and Rackspace Cloud Files.   However, I only back up online a portion of my data — primarily digital photographs and some documents.  Even so with the way digital photos grow, when I return from holiday it can take several weeks to get the photos uploaded because I limit the upload to being hours during the night when my ISP doesn’t count bandwidth usage.  Nevertheless, Jungle Disk works in the background unobstrusively and I’ve found it reliable and easy to use.  There are many similar services such as Carbonite and Mozy.

Another challenge for maintaining data is that when internal drives are not large enough to hold all of our data, then some of it will be moved to external drives.   Also external drives may be more convenient for sharing some sorts of data.   For example, my iTunes library on my iMac is on an external drive, and I shall probably have to split my iPhoto library into separate libraries some of which are on external drives.   In this case, again one needs to ensure that this data is stored in multiple places.  Time Machine can back up external drives but this is mostly going to be impractical unless one has a very large Time Machine drive and only small amounts of data held on external drives.  Another option is to regularly copy or clone the external drives.  Again SuperDuper or Carbon Copy Cloner can be used for this.  Also another possibility, is to use the built in rsync on Mac OS (or perhaps more easily the GUI interface arRsync) to keep two directories in synchronisation with one another.  An alternative method which I have used is to take advantage of the built in software RAID facilities in Mac OS X.   Disk Utility has the capability to set up two external drives (or partitions on external drives) in a RAID configuration.  These can be either mirrored (known as RAID 1, the OS mirrors one partition to the other), or striped (known as RAID 0, the OS splits data between the drives for faster access).  Disk Utility also allows the creation of volumes that span multiple drives (known as Just a Bunch of Disks).  For more information open up Disk Utility and go to the Help entry for Using RAID sets.  I’ve used this on my MacMini for managing media which are mirrored between two hard drives (the internal hard drive is no where near big enough).  I’ve also used it on my iMac with two external drives to mirror my iTunes library into which I progressively ripping my classical CDs (usually at a lossless setting).  This seems to work quite well although I’ve found that it can be tricky making sure that two disks come back online within the appropriate time interval when switching the machine on or rebooting.   If one of the drives doesn’t spring to life within the appropriate time it will be treated as damaged and the OS will continue using the other drive and then if the first one comes up the OS will recopy all of the data again.   (There is a setting in the command line version of Disk Utility to set the timeout — run “man diskutil” in a terminal window.)  This is probably most useful on machines that are never powered down (which is true of my MacMini, and mostly true of my iMac).  However, even in this case there is a need still to have a third copy of the data somewhere, preferably off site.

Probably the most painless way of achieving hardware redundancy but at a cost is the use of a Drobo.   This is a hardware RAID-like solution (“BeyondRAID”) which allow one to use a mixture of disks of various sizes and manufacture and the Drobo manages the drives such that one or more failures (depending on the product) can be tolerated.  It is also possible to hot swap drives.  They are very impressive and I’ve heard many good reports about them but haven’t used one myself, although I think I might well buy one next year as I’m getting to the stage of having so many odd external drives that it becomes difficult to manage.  It is possible to store a Time Machine on a Drobo in which case it provides redundancy for the Time Machine backup — although one still needs to think about an offsite back up of some form.

I mentioned e-mail at the beginning of this blog.   Obviously e-mail can be backed up with the rest of the Time Machine and cloned back ups, but another solution to e-mail is the application MailSteward which can be used to simply to archive e-mail to an external drive, but it also provides some very powerful indexing and database structures to rapidly search those many years of e-mail that all of us accumulate.  Obviously for many individuals retention of e-mails is not necessarily a problem, but anyone running a business will be aware of the need to retain large volumes of e-mail records.




Hard Drive Problems

Tuesday, August 3rd, 2010

This blog seems to be collapsing in to a tale of hardware / software problems, but I guess that these are the things that have been on my mind the last few weeks.

I had a rather strange hard drive problem recently.   It concerned a 500GB Western Digital external USB drive (one of the basic models).  I don’t use it heavily — it isn’t really part of my normal workflow, but it contains archived material which is not particularly essential although I would be sorry to lose the contents.   It is divided into two partitions — mostly for historical reasons that it itself replaced two smaller previous disks used for the same purpose.  I noticed one evening that only one of the partitions was showing up — something which I really couldn’t understand.  If OS X can see the disk it ought to be able to see both partitions not just one.   I thought that perhaps I’d unmounted one of the partitions, but a check with Disk Utility showed that OS X was only seeing the drive as a much smaller drive containing one partition.  Furthermore, it didn’t seem to be showing the files I expected within the partition that it could see.

Having bought Disk Warrior a while ago (and found it useful from time to time), I tried applying Disk Warrior to the drive.   I guess that because of the way that Disk Warrior works, it also could only see a smaller one partition drive, but if set to work it was claiming to be able to recover a lot more files.   I decided that I really didn’t want Disk Warrior to change anything at this time, because I realised that at least part of the problem was that the partition table wasn’t being read correctly — in fact it appeared that it was being read as the wrong format.

I started researching open and closed source packages that might help with resolving the problem.   Of the commercial packages “Data Rescue 3” looked like it might be a possibility but it isn’t particularly cheap.   Open source tools such as gparted seemed to largely involve building a boot CD which I wasn’t sure would actually work on the Mac, or testdisk had not yet been recompiled for Intel Macs and so needed Rosetta (which I’ve not installed since upgrading to Snow Leopard).  It being late in the evening I abandoned trying to do anything else and put it on my list of things to do some spare weekend.

Then the strange thing happened ….

The following day (or perhaps two days later), I plugged in the hard drive again and it came up perfectly as two partitions with all of the contents intact as if nothing had happened.

Clearly, something is not quite right with the drive although there has been no repeat of the problem since.  However, I did go out and buy another external drive (this time a Lacie external drive — not that I’m any great cheerleader for Lacie as I had a network drive from Lacie that failed just outside of warranty) and backed up the contents to the (twice as large Lacie).   In fact I think I’ll try to keep using the WD drive for the moment, but each time I modify it I’ll back up to the Lacie.

One of the nice things about the Mac is that rsync is built in to the OS which is a great command line tool for backing up or cloning data files.   However, to make it easier for myself (this must be a sign of old age), I downloaded a copy of arRsync (a gui front end for rsync) which saves me remembering all of the parameters needed by rsync.


iPhoto problem

Sunday, August 1st, 2010

My daughter had a problem with iPhoto on her MacBook.  It wouldn’t create any slideshows.  We checked for software updates and her machine was up to date except for the latest Safari update which we installed and which had the possible benefit of causing a reboot.   I did all the other things that I usually do to solve problems: used DiskUtility to verify the disc and also to repair permissions (there were a lot of permissions problems — although none of them appeared to relate to iPhoto — mostly they seemed to relate to Airport).  Fortunately, she hasn’t got a lot of stuff on her MacBook — only about 40GB so these scans were a lot faster than on my MacBook.  This didn’t solve the problem.

We next tried iPhoto in another user, and that worked perfectly so it appeared definitely to be a problem associated with her user account.   At this point we looked in to the ~/Library/Preferences directory to find anything for iPhoto and dragged the preference file out to the desktop.  I’ve often read about preference files causing problems but up until now this has never solved a problem for me.  However, this time we restarted iPhoto and of course it went through all of the “first time” messages but everything then worked perfectly.  So for the first time for me, trashing a preference file solved a problem.   I assured her that it was probably not anything she had done — more likely iPhoto had terminated unexpectedly and left the preference file in some incorrect state.  Anyway, she can now build slideshows again.