[mythtv-users] Adding an SSD to my MBE -- partitioning question

[R. G. Newbury]

On 02/13/2012 10:30 AM, Mark Lord wrote:
> On 12-02-13 09:32 AM, Mark J. Small wrote:
>>
>> In previous discussions about SSD's some folks suggested moving /tmp off the
>> SSD to keep it from wearing out, especially when there isn't a lot of spare
>> RAM to help mysql when the scheduler is run.  I was planning on using some of
>> the unpartitioned space on sdb for this.
>
> Your mechanical drives will be long dead and replaced at least once or twice
> before you ever wear out a modern SSD (assuming the SSD doesn't hold recordings).
>
> Most important thing to do:  ensure each partition on the SSD is aligned to
> an even power of two.  Eg. partition-1 should start at sector 64,
> rather than the (old) default of sector 63.
>
> And no need to bother with a separate /boot partition.

It is actually a 2048 sector alignment which works best. See here:

http://randomtechoutburst.blogspot.com/2010/03/4k-alignment-for-disks-important.html

Recent distro releases have started to use gpt partitioning (Fedora 16). 
If you want to continue to use the old-style (ms-dos) partition 
methodology, you should partition your new drive BEFORE commencing the 
installation.

Use gparted or such from a 'rescue disk' or USB key. I prefer 
System-Rescue-CD. What you want to see when you are done is something 
like this:

sfdisk -uS -l

Disk /dev/sda: 7297 cylinders, 255 heads, 63 sectors/track
Units = sectors of 512 bytes, counting from 0

    Device Boot    Start       End   #sectors  Id  System
/dev/sda1   *      2048  51206143   51204096  83  Linux  #this is 'root'
/dev/sda2      51206144  92166143   40960000  83  Linux  # home
/dev/sda3      92166144 110598143   18432000  83  Linux  # /usr/local
/dev/sda4     110598144 117229567    6631424  83  Linux  # /var

Note that the start sectors are all divisible by 2048. The '-uS' tells 
sfdisk to report in sectors not cylinders or bytes.

As to HOW you should partition, this is my thinking (and see above!)

Root will get updated and amended. You may want/need to re-install.
Home will NOT get formatted or updated and can carry forward through 
many updates. Just create the same user each time
/usr/local contains your myth programs and personal scripts Does not get 
formatted on upgrade
/var : where all the logging goes. If your system breaks and starts 
logging thousands of reports, it is not fatal to the system if the 'var' 
partition fills up. Things will still run, but odd things will happen 
since the system cannot write to /var. Delete some files and things will 
go back to normal. If you fill '/', you will likely end up re-installing 
as things can get ugly (not saying you cannot recover but it will not be 
easy).

Because /var is sacrificial, I put /var/lib/mysql and /var/www in 
/home/mythtv and put symlinks in their places. Again, var can be wiped 
clean without destroying your data. And myth CAN write lots of error 
messages if things go pear-shaped.

I have 4G RAM and dispense with a swap partition, both here on the 
desktop and on the mythbox.

The tv recordings are saved to /video on a 1TB /dev/sdb1 partition, 
along with copies of the important stuff. I save a copy of the installed 
/etc, /home/mythtv/, /usr/local, and /root. I cron a backup of the 
mythconverg database to /video early every morning.

/dev/sda partitions all use ext4. /video uses xfs with 
'alloc-size=512M'. That switch pre-allocates a half Gig at a time for a 
file being recorded. This means that the file goes down in contiguous 
half Gig chunks on the disk. Helps reduce fragmentation.

Geoff