I'm considering my current system and trying to determine the best way to
allocate drive space. System currently has the following drives installed:
120g ATA (backups), 500g SATA (mp3, audio, etc.), 500g SATA (videos), 400gig
(data, documents, downloads), 300g SATA (/, home, var, etc...). I also have
a 500g ATA drive not currently in use.

It sounds like I should sell my 300g and 400g drives and get another 500g
and move to Raid5.

This is how I see the pros and cons of LV vs RAID5. Does this sound right?

Logical Volumes:
+ use any size drives without losing usable space
- Any drive fails and your filesystem is damaged. You WILL lose data.
- Data fills one drive, then the next, etc. You could lose a large percent
of your data if the first drive fails.

Raid5:
+ Any single drive failure does not cause any loss of data
+ Only requires the space of one drive to store parity. More drives means a
lower percentage of space allocated to parity. (5x100gig in Raid5 gives 400g
of usable space. 2x250gig in Raid5 gives only 250gig of useable space)
? Parity and Data is spread evenly across multiple drives.
- All drives in the array need to be the same size or you will waste usable
space on the larger drives.

So anyway, it was like, 16:06 CET Nov 06 2007, you know? Oh, and, yeah,
Noozer was all like, "Dude,

> I'm considering my current system and trying to determine the best
> way to allocate drive space. System currently has the following
> drives installed: 120g ATA (backups), 500g SATA (mp3, audio, etc.),
> 500g SATA (videos), 400gig (data, documents, downloads), 300g SATA
> (/, home, var, etc...). I also have a 500g ATA drive not currently
> in use.
>
> It sounds like I should sell my 300g and 400g drives and get another
> 500g and move to Raid5.
>
> This is how I see the pros and cons of LV vs RAID5. Does this sound
> right?

If you ask me, the two are not mutually exclusive (since they solve
different problems), but rather complement each other. I'd use logical
volumes with RAID5 (or 6, if you want that extra redundancy).

In your case, you'd in fact have four 500 gig drives to work with if
you went along with the plan, which is pretty ideal for a RAID5 setup.
You'd have (more or less, depending on how you count the bytes) 1.5TB
(1TB with RAID6, but then you'd be safe from any two disk failures)
worth of storage with the freedom to resize volumes and you could lose
any of the drives without losing data.

--
Time flies like an arrow, fruit flies like a banana. Perth ---> *
16:22:03 up 14 days, 6:51, 2 users, load average: 0.15, 0.07, 0.07
Linux 2.6.23 x86_64 GNU/Linux Registered Linux user #261729

"Johan Lindquist" <spam@smilfinken.net> wrote in message
news:qnd605-tip.ln1@news.smilfinken.net...
> So anyway, it was like, 16:06 CET Nov 06 2007, you know? Oh, and, yeah,
> Noozer was all like, "Dude,
>
>> I'm considering my current system and trying to determine the best
>> way to allocate drive space. System currently has the following
>> drives installed: 120g ATA (backups), 500g SATA (mp3, audio, etc.),
>> 500g SATA (videos), 400gig (data, documents, downloads), 300g SATA
>> (/, home, var, etc...). I also have a 500g ATA drive not currently
>> in use.
>>
>> It sounds like I should sell my 300g and 400g drives and get another
>> 500g and move to Raid5.
>>
>> This is how I see the pros and cons of LV vs RAID5. Does this sound
>> right?
>
> If you ask me, the two are not mutually exclusive (since they solve
> different problems), but rather complement each other. I'd use logical
> volumes with RAID5 (or 6, if you want that extra redundancy).
>
> In your case, you'd in fact have four 500 gig drives to work with if
> you went along with the plan, which is pretty ideal for a RAID5 setup.
> You'd have (more or less, depending on how you count the bytes) 1.5TB
> (1TB with RAID6, but then you'd be safe from any two disk failures)
> worth of storage with the freedom to resize volumes and you could lose
> any of the drives without losing data.

I don't follow how I could use both LV and Raid5 together with four 500g
drives...

Would I use Raid5 to create a 1.5g PE and then create a single LV filesystem
on that PE? If so, how would I go about growing the filesystem later with
another 500g drive?

Noozer wrote:

> Logical Volumes:
> + use any size drives without losing usable space
> - Any drive fails and your filesystem is damaged. You WILL lose data.

Depends on your LVM system setup, LVM supports mirroring in the same way as
Raid1, so no data loss is necessary.


> - Data fills one drive, then the next, etc. You could lose a large percent
> of your data if the first drive fails.

Or you could loose all data, if you setup a LVM stripe without mirroring, in
the same way as you would use Raid0.


--

//Aho

So anyway, it was like, 18:10 CET Nov 06 2007, you know? Oh, and, yeah,
Noozer was all like, "Dude,

[..]

> Would I use Raid5 to create a 1.5g PE and then create a single LV
> filesystem on that PE? If so, how would I go about growing the
> filesystem later with another 500g drive?

Adding another drive to the array will increase the space of the
device, after that you should be able to grow the physical volume
using pvresize. After that, add or resize logical volume(s) on the
physical volume.

--
Time flies like an arrow, fruit flies like a banana. Perth ---> *
12:02:46 up 15 days, 2:31, 2 users, load average: 0.05, 0.08, 0.08
Linux 2.6.23 x86_64 GNU/Linux Registered Linux user #261729

"Johan Lindquist" <spam@smilfinken.net> wrote in message
news:ovi805-u94.ln1@news.smilfinken.net...
> So anyway, it was like, 18:10 CET Nov 06 2007, you know? Oh, and, yeah,
> Noozer was all like, "Dude,
>
> [..]
>
>> Would I use Raid5 to create a 1.5g PE and then create a single LV
>> filesystem on that PE? If so, how would I go about growing the
>> filesystem later with another 500g drive?
>
> Adding another drive to the array will increase the space of the
> device, after that you should be able to grow the physical volume
> using pvresize. After that, add or resize logical volume(s) on the
> physical volume.

I see... So, without LV I can't just add a drive to the Raid5 array and grow
the filesystem?

So anyway, it was like, 12:43 CET Nov 07 2007, you know? Oh, and, yeah,
Noozer was all like, "Dude,
> "Johan Lindquist" <spam@smilfinken.net> wrote in message
> news:ovi805-u94.ln1@news.smilfinken.net...
>> So anyway, it was like, 18:10 CET Nov 06 2007, you know? Oh, and, yeah,
>> Noozer was all like, "Dude,

>>> Would I use Raid5 to create a 1.5g PE and then create a single LV
>>> filesystem on that PE? If so, how would I go about growing the
>>> filesystem later with another 500g drive?
>>
>> Adding another drive to the array will increase the space of the
>> device, after that you should be able to grow the physical volume
>> using pvresize. After that, add or resize logical volume(s) on the
>> physical volume.
>
> I see... So, without LV I can't just add a drive to the Raid5 array
> and grow the filesystem?

You might be able to extend an ext partition without LVM (not sure on
the details here), but the advantages of using LVM instead of fdisk
for managing partitions and disk space are, to me, reason enough to
use it on my systems.

I generally set up two RAID devices, the system partitions exist on
a mirrored set of disks (RAID1) and the user data on a larger RAID5
device, usually a single volume. I use LVM on both arrays to manage
partitions, and if I ever have to resize a partition, LVM makes it
fairly easy to do so and even keep the partitions continous.

--
Time flies like an arrow, fruit flies like a banana. Perth ---> *
13:26:13 up 15 days, 3:55, 2 users, load average: 0.15, 0.13, 0.09
Linux 2.6.23 x86_64 GNU/Linux Registered Linux user #261729

On Tue, 06 Nov 2007 15:06:59 +0000, Noozer wrote:

> I'm considering my current system and trying to determine the best way
> to allocate drive space. System currently has the following drives
> installed: 120g ATA (backups), 500g SATA (mp3, audio, etc.), 500g SATA
> (videos), 400gig (data, documents, downloads), 300g SATA (/, home, var,
> etc...). I also have a 500g ATA drive not currently in use.
>
> It sounds like I should sell my 300g and 400g drives and get another
> 500g and move to Raid5.
>
> This is how I see the pros and cons of LV vs RAID5. Does this sound
> right?

Right now I've got a honking-ass kicker Fedora Core6 system and a F7
laptop. I went to the point of ripping out LV from the FC6 system, but
(don't know why) left LV on the F7 system. Right about now, I'm kicking
myself. LV seems to be a major boon.

On the FC6 system, I've got about 300+G dedicated to music and 300+G
dedicate to video, with 300G dedicated to OS. This is possibly the
stupidest SysAdmin thing I've done in 15 years.

On the F7, I've got a cheezy 80G drive, with a / partition, with
everything else on a LV. This approach is *much* better -- as I travel,
the stuff on the LV can expand/contract as I get various downloads
(podcasts, family guy, etc etc).

In short; I wish I would've put my Video+Music on a single 600G LV
partition (the music is filling up, while the video is ludicrously low on
utilization). Right now, backups are to a different system with a 500G
disk drive there.

If you're asking; I'd put all Music/Video on a single LV, put "/" and
boot on local real partitions, the rest of the OS on a LV. Keep the
backup disk as separate partition (or LV group if you've more than one),
and replicate your precious data there....