SSD+HDD RAID+lvm2 formatting strategy help.

[1clue]

Hi everyone.

I recently had a system failure, a drive went bad. I grabbed my data on a removable and set about installing Gentoo again. I had 4x750g drives set up as LVM2 with a removable drive for backups. I actually kept backups, so nothing really lost here but hardware. I couldn't find my exact drive anywhere. The other 3 have no faults.

I picked up a Corsair Force 3 240g drive. This is a lower-cost drive from a company I like for memory products.

I hadn't really planned to get an SSD so I have no plan, I'm caught with my pants down. I'm going through http://en.gentoo-wiki.com/wiki/Solid_State_Disk and getting some questions.

I had thought that SSDs required a scatter filesystem to prevent too many writes in one spot. The wiki says this is false because SSDs have a controller which takes this into account. The documentation on this drive don't say anything about that, and since it's a lower cost model I wonder if it has the controller, or if they just didn't mention it. Is there some way I can tell?

If these were all spinning disks, my /boot would be raid1x4 from each drive, swap would be four single SWAP partitions (no RAID) and everything else would be RAID with LVM2 on top. Everything except /boot would be EXT4 or XFS or Reiser, because those filesystems can be resized while mounted and they cover all my data needs.

Here's my modified strategy, somebody please check sanity on this and offer advice.

SSD format:

1. /boot
   
2. LVM2 vg=ssdvg
   

HDD format, all identical, 3 disks:

1. 12g SWAP
   
2. 400g RAID vg=raid5vg
   
3. * RAID vg=raid0vg
   

The HDD format is basically what I had before. I have 12g RAM. I have a lot of SWAP defined, but I use TMPFS for /var/tmp/portage and a few other places, and have never actually touched a SWAP partition other than for hibernate. My prior filesystem map actually looks a lot like the SSD wiki recommendations.

I have 2 partitions for RAID on each spinning disk, and generally mix modes. I would use the 400g partition for RAID5 (RAID6 if I had all 4 disks) and maybe raid 0 for the remainder of the disk for a quick data dumping ground for non-critical data.

I also have a large removable disk with xfs on it, used for backups.

Thanks in advance.

[VinzC]

Indeed SSD have everything needed to use all the memory cells efficiently without requiring any particular filesystem. You might also want to read an article I found lately about SSD. An interesting feature is the elevator=noop kernel argument; SSD don't need clever I/O scheduling and all I/O requests can pass-thru without impacting performance. If you're curious .

EDIT: BTW I would place on the SSD only what changes rarely, just to make sure the drive lasts the longest possible. So I'm not Sure LVM is a wise option here... unless you dedicate a specific group and physical volume to it. So filesystems such as /var, /run and /home are best out of an SSD.
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[1clue]

VinzC,

Thanks for the response.

I'm reading your article now, but does elevator=noop affect my spinning drives?

The ssd would be its own volume group, all it would give me is adjustable partition sizes.

I will probably have 2 volume groups on the spinning array.

Thanks.

[1clue]

Can I do root partition on LVM?

My current thought is no, I've never done it that way. But I'm curious.

Thanks.

[darklegion]

[VinzC]