40GB SSD as system + 500GB Hdd as home

[attila_66]

Yesterday I bought a 40 GB SSD drive (Corsair F40) and a WD 500Gb Hdd.

I plan to install the system (root) on the 40gb SSD and use 500GB hdd as my home directory.


What i plan is to make manual partitions on the drives.
36gb partition of SSD will have / mount point 4 gb swap area on SSD and Hdd will have /home mount point.

Is my plan ok or not?

[skunk]

Re: 40GB SSD as system + 500GB Hdd as home

I would advise against placing the swap partition on the SSD. I understand that SSDs have a limited numbed of write cycles before failing and anything that writes often to disk will be baaaaaad. Some people even advise against having /var on a SSD for the same reason.

[dibl]

Re: 40GB SSD as system + 500GB Hdd as home

Your plan will work, however, you need to make a study of several topics to get the most out of your SSD.

1. Partition Alignment -- if you are using the 40G drive as a single partition, then perhaps it doesn't matter (you could put swap on the hdd). But I would still review the guidance for aligning Corsair SSDs here: http://forum.corsair.com/v3/forumdisplay.php?f=188

I recently installed Debian on a 40GB OCZ Vertex 2, and did the alignment using fdisk, following this:

http://www.ocztechnologyforum.com/fo...l=1#post373226


2. Filesystem tweaks. ext4 will be a good filesystem, but you should slow down the journal writing, use "noatime" and perhaps other options that reduce unneeded disk writes, and mount /tmp to a tmpfs filesystem, so it runs in memory and not on the SSD. Here are a couple of links to help:

http://www.cyrius.com/debian/nslu2/linux-on-flash.html

http://cptl.org/wp/index.php/2010/03...ives-in-linux/

Here is the /etc/fstab file for my netbook with the OCZ SSD in it -- note the mount options:

UUID=42e0cce2-17f9-4452-ab24-f40d79e18ebc   /          ext4    defaults,noatime,errors=remount-ro,barrier=0,discard,commit=120 0 1
UUID=64097124-3a9a-45e1-a051-d470805bab1d   none         swap    sw 0 0
UUID=57281ba2-b8a0-4c5c-ae4f-a1048408752c   /home        ext4    defaults,noatime,errors=remount-ro,barrier=0,discard,commit=120 0 2
none                     /tmp         tmpfs   defaults,noatime,mode=1777 0 0

Here is the last part of the /etc/sysctl.conf file, where the virtual memory behavior is tweaked:

.
.
.
#
# Log Martian Packets
#net.ipv4.conf.all.log_martians = 1
#
vm.swappiness=1
vm.vfs_cache_pressure=25
vm.dirty_writeback_centisecs = 12000
vm.dirty_expire_centisecs = 12000
vm.dirty_ratio = 10
vm.dirty_background_ratio = 2
#

[oshunluvr]

Re: 40GB SSD as system + 500GB Hdd as home

Sounds OK to me - you might want to have a partition on the HD to back up your SSD since you'll likely have the space.

Other options: Since your SSD is so big (8gb is enough for kubuntu);

You could leave /home on the SSD and symlink to the hard drive. Thus having quicker access to your settings and such, while keeping your larger data - docs, pics, music... on the HD.

You could use a separate /tmp and use a smaller install partition so if you wanted to try a new release or distro you could do a full install without endangering your primary install. You can allow all you installs to share the /tmp. Another good use for this is to have two kubuntu installs along side and then you can pre-test updates/upgrade or other experiments without leaving you with a broken install.

Here's how I see it:

SSD
partition1 4 gb swap
partition2 8 gb /tmp
partition3 8 gb kubuntu
partition4 - extended
partition5 4 gb /home
partition6 8 gb second install (kubuntu?)
partition7 8 gb third install (some other distro?)

HD
partition1 4gb /home backup
partition2 24gb SSD install partitions backup
partition3 472gb file storage

The sizes will be a little different depending on how many actual bytes are on each device (drive makers have funny math) but you get the idea I think.

Bottom line - your idea is fine too.

My personal setup is a little different than the above suggestion - I leave /home within all my installs (I have room for 6) and keep all my files separate on a partition I have mounted as "files" and linked to all my /home's. In the above setup - I assumed the /home would be used only for the primary install and backed up to the HD. The secondary installs would have /home within the install.

The main thing for you will be to do some research on what is the best file system to use on the SSD and to use the most beneficial options for speed and longevity.

[attila_66]

Re: 40GB SSD as system + 500GB Hdd as home

Thank you for all replies.

You could leave /home on the SSD and symlink to the hard drive. Thus having quicker access to your settings and such, while keeping your larger data - docs, pics, music... on the HD.

This is a good idea. But how to do this ??

It would be great to use my existing home hdd with the distro updates.
On every distro update I have to backup all my home (About 250GB) then restore it on the newley installed distros home.

Thank you Dibl for suggestions I will look also for tuning my SSD.

Since I have 4gb ram swap area is rarely used on my system so dont have to be afraid where ists located.

Sunday will be my working day on this system.

[wizard10000]

Re: 40GB SSD as system + 500GB Hdd as home

I have Kubuntu 10.10 installed on Corsair Extreme X64 - / is on the SSD, /home and swap are on a 1TB mechanical drive. No worries so far.

I've tried putting /tmp on a ramdisk (64 bit OS, 6GB RAM) but it made Kubuntu a little cranky - slow to respond sometimes and things stuttered a bit on boot but it ran pretty okay. I ended up leaving /tmp on the SSD.

[dibl]

Re: 40GB SSD as system + 500GB Hdd as home

This is a good idea. But how to do this ??

There is a bash command, but it is so easy with Dolphin that I'd recommend you do it that way.

Just install Kubuntu -- the entire fileystem -- on the SSD. Afterward, open Dolphin, split the window, and while you leave one pane on your /home directory, in the other pane browse to wherever your DOCS, MUSIC, PIX, VIDEOS, or whatever data you have. Highlight the applicable data folder, say your docs, and drag them across the split to the DOCS folder in your home directory, and drop them there. The pop-up menu asks "Move, Copy, Link Here?" and you choose "Link Here". Very simple.

[blobfish]

Re: 40GB SSD as system + 500GB Hdd as home

some questions about ssd:

I understand moving swap space off of the ssd for increased life expectancy, but it seems to me that having swap space on ssd would be one of the bigger performance benefits of having an ssd. Am I overvaluing swap?

On ssds, at what scope does failure occur? Lets say I put a 4GB partition swap space on a ssd and "wore it out". Would the whole ssd become unusable or just that 4GB partition?

I have fooled around with gpt partition tables and I really like the absence of the primary, logical and extended partition types. Is there any implications of gpt on ssds? I would guess not, but thought I would ask.

[dibl]

Re: 40GB SSD as system + 500GB Hdd as home

I understand moving swap space off of the ssd for increased life expectancy, but it seems to me that having swap space on ssd would be one of the bigger performance benefits of having an ssd. Am I overvaluing swap?

On ssds, at what scope does failure occur? Lets say I put a 4GB partition swap space on a ssd and "wore it out". Would the whole ssd become unusable or just that 4GB partition?

I have fooled around with gpt partition tables and I really like the absence of the primary, logical and extended partition types. Is there any implications of gpt on ssds? I would guess not, but thought I would ask.

The utility of swap on a SSD depends on your usage scenario. swap space has basically 2 functions in life:

1. To accommodate applications demand for memory space that exceeds your physical installed memory

2. To provide a place for "hibernate" aka "suspend to disk" aka "S2Disk" -- an image of the running memory

So, you will only "need" swap if #1 or #2 (or both) are applicable to your computer and your use of it. I put "need" in quotes -- meaning "your computer will lock and crash without it", as opposed to "you will feel nervous anxiety in your stomach if you don't see it being used".

Suppose, like me, you have a recent model netbook, with 2GB of installed memory, and all you normally do with it is run a browser, e-mail, play videos with flash or Kaffeine, listen to music while travelling, etc. Doing those things, you will never saturate the physical memory, so Reason #1 is N/A. But, suppose your travels take you to places and times when you do not know when your next opportunity to recharge the battery will come. So you're going for the absolute maximum battery life, and that means you would rather "S2Disk" than "S2RAM", because S2RAM keeps a trickle of battery power going all the time, and S2Disk absolutely shuts down the computer -- there's no battery consumption while it's hibernated. Therefore, you do want a swap partition (or a swap file), and you want it to be the size of your RAM, so there's no concern about how much is going on at the moment that you need to hibernate it.

As far as impact on the SSD, other things (like your browser cache, and system logging in /var/log) are going to do far more writing to the media than your periodic hibernate commands, so it's not credible, in the usage scenario above, that using swap for S2Disk will ever be the primary factor in determining the life of the SSD.

On the other hand, if your SSD is in a desktop system, where you push the system into swapping all the time by running multiple memory-hungry packages that need more memory than you have installed, then it is possible that you could could get more write/erase cycles going in the swap partition that anywhere else, especially if you have optimized it by mounting the /tmp and /var directories on tmpfs filesystems.

I'm still studying GPT and trying to figure out whether it has any ramifications for SSD partitioning and usage -- so far it's not obvious that it does. But it is obvious that you want to understand how partition alignment works, and what the erase block size of your SSD is, so you can align your partition starting cylinders.

Hope this helps.

[Snowhog]

Re: 40GB SSD as system + 500GB Hdd as home

I think, that in time, and likely not to much time, users, as well as the industry, are going to find that the trade-off of speed vs life of SSDs isn't worth it. Prices for SSDs having the same capacity of a HDDs are much higher. Why would you want to spend so much more for something that won't last nearly as long as a HDD? Don't get me wrong, there are definitely places where SSDs are needed/desired. But I wouldn't use one where read/writes are the norm.

[dibl]

Re: 40GB SSD as system + 500GB Hdd as home

the trade-off of speed vs life of SSDs isn't worth it. Prices for SSDs having the same capacity of a HDDs are much higher. Why would you want to spend so much more for something that won't last nearly as long as a HDD?

As a pure value judgment, that would be more true if the situation were static, but it isn't. Prices for SSDs are falling (maybe not as fast as hdd prices), SSD capacities are increasing, and (perhaps most importantly) the performance capabilities are far surpassing anything that we will ever see from conventional drives. So, if the purchase decision is strictly "GB/$", then hdds win, but for those enthusiastics who will pay a premium for better performance, SSDs are looking very attractive already, and still improving. SATA 3, at 6GB/s transfer speeds, won't ever be saturated by conventional hdds, as far as I can learn -- they've hit their performance limits. SSDs are still developing improved performance, and when SLC nand begins to replace MLC nand flash memory in consumer devices, they will become even more attractive to the "performance-oriented" consumer, even while the cost per GB continues to decline. That's my opinion.

[attila_66]

Re: 40GB SSD as system + 500GB Hdd as home

This is a good idea. But how to do this ??

There is a bash command, but it is so easy with Dolphin that I'd recommend you do it that way.

Just install Kubuntu -- the entire fileystem -- on the SSD. Afterward, open Dolphin, split the window, and while you leave one pane on your /home directory, in the other pane browse to wherever your DOCS, MUSIC, PIX, VIDEOS, or whatever data you have. Highlight the applicable data folder, say your docs, and drag them across the split to the DOCS folder in your home directory, and drop them there. The pop-up menu asks "Move, Copy, Link Here?" and you choose "Link Here". Very simple.

Did it this way but asks for password to access HDD.

[dibl]

Re: 40GB SSD as system + 500GB Hdd as home

I hope your /home/user folder is not owned by root! Better right-click it with Dolphin and see what it says on the "permissions" tab. Then do the same thing with the source folder where you are linking from. I fear one of them is owned by root.

The default owner of hard drives and partitions is root. I don't recommend changing that. It's better to make directories (aka "folders") on the mounted partition(s), and make your user the owner of the folder(s) and contents. So, if your partition (or entire drive) is mounted on /mnt as "sdb1" for example, you would do:

sudo mkdir -p /mnt/sdb1/MUSIC

to make a new directory named "MUSIC" on it. But the new directory is still owned by root.

During installation of Kubuntu, your /home/user folder was created with you (the user) as the owner, not root.

To change the ownership of a directory and its contents, from your KDE desktop you can open Dolphin with Super User privileges:

Alt-F2 "kdesudo dolphin" with no quote marks, and give the password. Browse to /mnt/sdb1/MUSIC, and right-click on the folder. Click the "permissions" tab, and note that the user and group both say "root". Change these to your user's name, and "x" the box where it says "apply to changes to subfolders", and then "Apply" and you now have a folder owned by your user, where you can save data, or link it to your /home/user/music folder.

Don't use Dolphin in Super User mode for anything that you don't require root privileges for -- you can lose access to your home folder if you save anything in it "as root".

Also, the bash command that you (with "sudo" prefix) can use to change the ownership of a file or folder is "chown", if you prefer to work in the terminal.

[attila_66]

Re: 40GB SSD as system + 500GB Hdd as home

After some install and systemcrash tests decided to make clean install "System on SSD" and "Home on HDD".
(no home on SSD)

Since I dont care about the life of SSD no modification is also done on journaling of Ext4 file system.

Thank you again for all suggestions and information.

[blobfish]

Re: 40GB SSD as system + 500GB Hdd as home

Maybe this article would add more to this ssd discussion.

http://www.zdnet.com/blog/perlow/gee...and-linux/9190

I know, I know its zdnet, but not everyone there is Ed Bott.