raidreconfig advice

raidreconfig advice

[Max Waterman]

OK, I am going to try to expand the capacity of my raid5 array and I 
want to make sure I've got it right.

So, first thing to check is that they are identical drives. I figure 
fdisk is enough :

foreach disk ( `cat /proc/diskstats | perl -ne '{ /((hd|sd)[a-z])\s+/; 
print "$1\n" if ( $1 ) }'` )
foreach? /sbin/fdisk -l /dev/$disk
foreach? end

Disk /dev/hda: snip...

Disk /dev/hdg: 200.0 GB, 200049647616 bytes
255 heads, 63 sectors/track, 24321 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/hdg doesn't contain a valid partition table

Disk /dev/hdi: 200.0 GB, 200049647616 bytes
255 heads, 63 sectors/track, 24321 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/hdi doesn't contain a valid partition table

Disk /dev/hdk: 200.0 GB, 200049647616 bytes
255 heads, 63 sectors/track, 24321 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/hdk doesn't contain a valid partition table

Disk /dev/sda: 200.0 GB, 200049647616 bytes
255 heads, 63 sectors/track, 24321 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sda doesn't contain a valid partition table

Disk /dev/sdb: 200.0 GB, 200049647616 bytes
255 heads, 63 sectors/track, 24321 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sdb doesn't contain a valid partition table

Disk /dev/sdc: 200.0 GB, 200049647616 bytes
255 heads, 63 sectors/track, 24321 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sdc doesn't contain a valid partition table

Disk /dev/sdd: 200.0 GB, 200049647616 bytes
255 heads, 63 sectors/track, 24321 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/sdd doesn't contain a valid partition table
[mwaterman@localhost /proc]$

My current RAID5 is on hd[gik] (hdm is RMAd), plus /dev/sdd as a spare.

I have sd[ab] as a RAID0 containing a backup.

This leaves me with sdc which I can try to add. If that goes OK, I'll 
trash the backup and add sd[ab] too.

1) Do the disks look identical (they're all WD2000, but some are PATA 
and some SATA).

2) Where do I get raidreconfig from? Google wasn't much help.

3) Are there any instructions for raidreconfig? I understand is uses 
some non-mdadm config files as from/to input.

4) I use xfs. Has anyone used xfs_growfs?

Thanks.

Max.

Re: raidreconfig advice

[David Greaves]

> 4) I use xfs. Has anyone used xfs_growfs?

Yes - it's been flawless.
I've used it on lvm2 over md

David

Re: raidreconf advice

[Max Waterman]

thanks.

Also, I note that the tool is called raidreconf, not raidreconfig, as I 
had in my original email.

Max.

David Greaves wrote:
> 
>> 4) I use xfs. Has anyone used xfs_growfs?
> 
> 
> Yes - it's been flawless.
> I've used it on lvm2 over md
> 
> David

Re: raidreconfig advice

[Mike Hardy]

Max Waterman wrote:
> OK, I am going to try to expand the capacity of my raid5 array and I 
> want to make sure I've got it right.

Not a bad idea, as its all or nothing...

> Disk /dev/hdg: 200.0 GB, 200049647616 bytes
> Disk /dev/hdi: 200.0 GB, 200049647616 bytes
> Disk /dev/hdk: 200.0 GB, 200049647616 bytes
> Disk /dev/sda: 200.0 GB, 200049647616 bytes
> Disk /dev/sdb: 200.0 GB, 200049647616 bytes
> Disk /dev/sdc: 200.0 GB, 200049647616 bytes
> Disk /dev/sdd: 200.0 GB, 200049647616 bytes

They certainly all looked the same (including the C/H/S counts)

> This leaves me with sdc which I can try to add. If that goes OK, I'll 
> trash the backup and add sd[ab] too.

I'd be very wary of this, for two reasons. One, you have the backup 
during the add for a reason. If anything goes wrong, there goes your 
data. Second, where would you ever back your raid up to? What about fs 
corruption?

The rule of thumb with databases is to always have enough contiguous 
scratch space to dump and restore your biggest table. With large RAID, 
you should always be able to dump and restore your largest raid device, 
imho. Its a bunch more disk yes, but you'll need it at some point, I 
promise. Many future tears can be averted...

> 2) Where do I get raidreconfig from? Google wasn't much help.

I saw you noticed it raidreconf - you should be set there

> 3) Are there any instructions for raidreconfig? I understand is uses 
> some non-mdadm config files as from/to input.

the man page is great - honest. Two conf files (current and future) and 
you're set

The last question should be an open-ended "is there anything else"?

1) Run a long SMART test on all drives first. Imagine if you get a bad 
block during the reconfig...
2) Validate your backup (just in case)
3) ?? It takes a long time to do, be patient I guess
4) You could use the script I posted earlier that sets up a loopback 
device practice raid set to practice perhaps (if you really wanted)

Good luck-
-Mike

Re: raidreconfig advice

[Max Waterman]

Mike Hardy wrote:
> 
> 
> Max Waterman wrote:
> 
>> OK, I am going to try to expand the capacity of my raid5 array and I 
>> want to make sure I've got it right.
> 
> 
> Not a bad idea, as its all or nothing...
> 
>> Disk /dev/hdg: 200.0 GB, 200049647616 bytes
>> Disk /dev/hdi: 200.0 GB, 200049647616 bytes
>> Disk /dev/hdk: 200.0 GB, 200049647616 bytes
>> Disk /dev/sda: 200.0 GB, 200049647616 bytes
>> Disk /dev/sdb: 200.0 GB, 200049647616 bytes
>> Disk /dev/sdc: 200.0 GB, 200049647616 bytes
>> Disk /dev/sdd: 200.0 GB, 200049647616 bytes
> 
> 
> They certainly all looked the same (including the C/H/S counts)
> 
>> This leaves me with sdc which I can try to add. If that goes OK, I'll 
>> trash the backup and add sd[ab] too.
> 
> 
> I'd be very wary of this, for two reasons. One, you have the backup 
> during the add for a reason. If anything goes wrong, there goes your 
> data. Second, where would you ever back your raid up to? What about fs 
> corruption?
> 
> The rule of thumb with databases is to always have enough contiguous 
> scratch space to dump and restore your biggest table. With large RAID, 
> you should always be able to dump and restore your largest raid device, 
> imho. Its a bunch more disk yes, but you'll need it at some point, I 
> promise. Many future tears can be averted...

I'm not worried about losing my data enough to make regular backups.
I recently thought I'd lost all my data - it wasn't that much of a 
shock. I since discovered I hadn't lost it all, so all is well.

I've made a backup onto a spare array, plus onto one of the 200GB disks 
which I will use as a spare later.

> 
>> 3) Are there any instructions for raidreconfig? I understand is uses 
>> some non-mdadm config files as from/to input.
> 
> 
> the man page is great - honest. Two conf files (current and future) and 
> you're set

Yeah, but I don't know how to use raidconf files. I use mdadm. I 
currently have in my mdadm.conf :

DEVICE /dev/hd[egik]
ARRAY /dev/md0 level=raid5 num-devices=4  devices=/dev/hd[egik]

I think my target mdadm.conf would be :

DEVICE /dev/hd[egik] /dev/sd[abc]
ARRAY /dev/md0 level=raid5 num-devices=7
devices=/dev/hd[egik],/dev/sd[abc]

What are these in raidtab(5) terms?

Max.