[SOLVED] SSD + 2HDD partitioning help.

Eurt · Last edited by Eurt on Mon May 14, 2012 5:23 pm; edited 1 time in total

Greetings. I've just purchased a 64GB SSD and a 1TB caviar black. I have the following:
sda is the SSD
sdb is the caviar black
sdc is my storage hdd
I want to use sda just for system, sdb just for software installation and sdc as storage.
The problem is I don't know how to split gentoo system (in sda) and portage installations (in sdb). Any advice?
Thanks.

NeddySeagoon · Posted: Wed May 09, 2012 6:07 pm Post subject:

Eurt,

Put /boot, / (root) and /usr on the SSD.
You don't need a separate /boot if you don't want it.
/ is the top level of the filesystem tree, /usr is where you system binaries go.
Swap here will be fastest but you may never need swap. You should have 512Mb of swap anyway, or swap=RAM if you want suspend to disk.

You can make separate partitions on your second drive for /var and /usr/portage and even /usr/portage/distfiles and /usr/portage/packages. I'll come back to /var in a minute
/usr/portage contains a large number of very small files. You can save space by making the block size 1k. Most of the files in the treee are smaller than that. If you use a 4k block sixe, you need four times as much space for your portage tree. Set the inode to block ratio to 1.

packages and distfiles contain mostly large tarballs, use a filesystem with 4k blocks and a lot of blocks per inode.
A separate /var may turn out to be a curse as newer udev needs it to be mounted before udev starts.

Put /home on either /dev/sdb or /dev/sdc

If you thing you will want to move space around, look into using Logical Volume Manager. My system looks like

Eurt · Posted: Wed May 09, 2012 7:06 pm Post subject:

The problem is that sda (SSD) will be shared by Windows and Gentoo, half and half, so I don't want to install every piece of software portage compiles into the ssd as I only have 30GB for each OS. My intention is to place just lib files in the ssd and the rest at another hdd. Should I mount /usr at sdb and /usr/lib32, /usr/lib64, /lib32, /lib64 at SSD?
By the way, thanks for the info

NeddySeagoon · Posted: Wed May 09, 2012 7:33 pm Post subject:

Eurt,

/lib, /lib32 and /lib64 must be on the root filesystem as programs in /sbin need them.
Consider what mount will do if its libraries are not on root. It will fail and nothing will mount.

You really don't want to split up /usr, other then moving portage out. You can have a separate /usr if you wish but this will lead to extra complexity when you move to >=udev-182.

What is your real objective in splitting up your system this way - what do you hope to achieve?
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

Eurt · Posted: Wed May 09, 2012 7:46 pm Post subject:

My target is to have this distribution:
sda (SSD) -> system
sdb -> programs
sdc -> storage

NeddySeagoon · Posted: Wed May 09, 2012 8:57 pm Post subject:

Eurt,

OK - but why?
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

Eurt · Posted: Wed May 09, 2012 10:01 pm Post subject:

Because I only have nearly 30GB for gentoo and to minimize writing to the ssd. I'll be using gentoo daily, as main OS (programming, studying...) and use windows just for gaming. That's why I think 30gb for installing programs won't be enaugh.

Arkhelion · Apprentice Joined: 07 Sep 2010 Posts: 151 Location: France

Hi,

I seriously have a hard time seeing how you could even approach 30GB for a root fs in Gentoo. If you keep your /home separated (absolutely no point to put it on an SSD), then 30GB is just huge!
For instance, I just checked my whole desktop system at home is 16GB and that's adding portage FS, logs, database files. Let's say (because that's what we are) you want to compile LibreOffice with your choice of USE flags you need an extra 10GB that'd make 26GB...

If you want to keep far from that, you could put your portage files on a separate partition like NeddySeagoon said. Now if you wanna install heavy softwares on your system, maybe games, you can always symlink /usr/games so that it won't clutter your root fs.
_________________
Arkhelion

NeddySeagoon · Posted: Thu May 10, 2012 6:20 pm Post subject:

Eurt,

My root plus /usr, without /usr/portage is 22G and I will have a few G of kernels in /usr/src, which can be moved out with a symlink, so say 20G.
Your 30G for root plus /usr looks fairly safe.

Why put gameloader OS on SSD if thats all it will be used for? The OS speed is not important there, its game data loading speed you are interested in.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

SDNick484 · Apprentice Joined: 05 Dec 2005 Posts: 231

I have a laptop (Lenovo T400) with a similar setup sda is a SSD and sdb is a HDD. Beyond the recommendations in the thread, I also suggest making /tmp (and possibly /var/tmp/portage) to be tmpfs. I have 8 GB on this laptop and this setup works well for me. It also has the advantage of reducing a number of small writes/erases on my SSD while still giving a performance boost. I have a 4 GB swap file, but I rarely hit it. I started using /tmp as a tmpfs after admining Solaris for a number of years (it's the OS default there).

Eurt · Posted: Thu May 10, 2012 9:19 pm Post subject:

Thanks for your answers, I'm building a good idea with those

Eurt · Posted: Thu May 10, 2012 9:26 pm Post subject:

NeddySeagoon · Posted: Fri May 11, 2012 5:19 pm Post subject:

Eurt,

/tmp on tmpfs is good, /var/tmp/portage is actually less important. If you have the RAM, the -pipe CFLAG has almost the same effect. That has the benefit of not invoking the OOM manager if you think you have enough RAM for /var/tmp/portage in tmpfs but really you don't.

All /var/tmp/portage in tmpfs gives you is the bragging rights to claim you can compile libre office in RAM and right now that needs 16G RAM.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

SDNick484 · Apprentice Joined: 05 Dec 2005 Posts: 231

Eurt · Posted: Fri May 11, 2012 9:28 pm Post subject:

Great info in this thread, seriously. Thanks everyone

.
I just did not realize something really important...
I'm using gentoo right now on my laptop as main OS, which actually is the only OS living in my 250GB HDD.
I'm analyzing disk usage with xdiskusage right now. Even though I have my system daily updated, with lots of programs, /usr just weight 14.74GB, I don't need anything more in my laptop so my PC /usr partition should weight at least the same. The other one is /home, which weights 50GB. That would be out of the SSD on my PC so isn't a problem. Finally, I have 11.53 GB occupied by inodes, which I actually have no idea of what they are. The rest of folders are irrelevant, they don't even appear in the graphic. So, keeping in mind that I'll be using about 15Gb of my SSD, I can install the gameloader in the SSD too.

NeddySeagoon · Posted: Sat May 12, 2012 10:58 am Post subject:

Eurt,

An i-node is a block of 128b or 256b, (its a filesystem creation option) used to store data about files. Each file needs at least one i-node, so you can get out of disk space errors either because you have no i-nodes left or the partition is full. Its space on disk the filesystem uses to store data about the files.
Some filesystems, e.g. the extX series, preallocate this space, others, e.g. reiser allocate space for this task as files are created.

The inode to data blocks ratio is set at filesystem make time and connot be changed.
For /usr/portage (just the tree) one inode per block is good as most files are smaller then one block

For /usr/portage/distfiles, which stores largw files, one inode per 1000 blocks may be ok.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

Eurt · Posted: Mon May 14, 2012 5:22 pm Post subject:

Thanks again! You all really solved my problems.

gcyoung · Posted: Thu Oct 04, 2018 6:51 pm Post subject: SSD drive

Have just aquired an SSD disk and have studied all of the above, and found it to be most helpful, Thanks to all.
I enquired of the vendor what the block erase size was and he didn't seem to know what that was, let alone the size itself.

Can anyone tell me if and how this can be obtained from the disk itself, or must I try and get this from the manufacturer ?
Also:--
Systemd and various other changes have taken place since the above was discussed. I note that on my current setup /dev /dev/sh /run and /sys/fs/cgroup are all installed (by gentoo), as a 'tmpfs's and /var/tmp/portage needs a minimum of 3.1G to function. There seems to be far more use of ram than formerly.

I don't see why /dev should not be placed on a secondary drive to spare some ram for /var/tmp/portage, since I am limited to 8Gig ram.

Any views/comments would be appreciated?