Topic: IBM eServer w/onboard ServRAID Card, 6 36g scsi drives

[jdanvers]

I've trolled though the forums here a bit and found one thread of someone who built an sme box on a compaq with a similar set up (h/w raid ctrl & 6 drives).  I have a similar machine available to me @work that I'm salvaging from the dumpster (corporate waste at its finest).

Seeking suggestions or advice:  Should I just let the raid manager auto-cfg all six drives as raid 5 where it uses 5 of the 6 and sets one aside as the hot spare (I think this is what it defaults to) or should I just glob 'em all together into a single array w/no hot spare?  I guess the question actually is - will sme see the spare drive?

Also - I'm hoping to get some storage out of this thing but am thinking that sme sets up a "mirror" by default - so what would I wind up with for usable storage if I just accept defaults?  Assuming sme wants to take 3 of the 6, and use the other 3 for the mirror - 36*3 = 108gig?  Or would it in fact go raid 5 and (assuming using all 6 drives) 36*5 = 180 gig usable?

Thanks guys....

-=- jd -=-

[janet]

jdanvers

Hardware drive devices are seen by sme as one drive, so other references you refer to relate to software control of drives to make software RAID.

Your hardware RAID will use whatever the controller is configured to do with the six drives, and present it to sme as one drive.

If you were able to use software RAID then as per FAQ & Raid howto sme will auto create RAID5 in a 5+spare arrangement. If you use the nospare switch at install time then sme will use all 6 disks in RAID5.

Also see the Booting howto.
Google RAID5 for final storage capacity depending how many drives you use.

[kevinb]

Comment: with six disks "SME nospare" will configure as RAID 6.

[janet]

jdanvers

RAID5 storage = (number of disks - 1) x smallest disk size
In your case = (5 - 1) x 36 = 144Gb

[jdanvers]

Thanks for the responses folks.  Long story short - I came across another old server that they were planning on tossing that had 4 73 gig (U320 15k's -- ) so I used those instead of the smaller 36'ers.  I configured the array to use all 4 w/no spare and just presented that to sme and let it do its thing.

73x4 = 292

This is what I wound up with:
[root@bigbubba ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/main-root
                      198G  9.3G  179G   5% /
/dev/md1               99M   24M   71M  26% /boot
none                 1014M     0 1014M   0% /dev/shm

So . . . I'm not sure what it (sme) decided to use on its own.  Appears to be raid 5'ish, but the numbers don't quite jive - 292-73=219 but I actually wound up with a 198g partition as shown above.

Whatever - the thing is WAY better than the previous machine that I was running off of
and I have lots more storage available that I did too.  ( my old "server" was an old circa 2001 pc w/a single 30 gig ide drive and 256m ram . . .   )  That old thing ran quite well for quite a few years though... 

[Stefano]

Thanks for the responses folks.  Long story short - I came across another old server that they were planning on tossing that had 4 73 gig (U320 15k's -- ) so I used those instead of the smaller 36'ers.  I configured the array to use all 4 w/no spare and just presented that to sme and let it do its thing.

73x4 = 292

This is what I wound up with:
[root@bigbubba ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/main-root
                      198G  9.3G  179G   5% /
/dev/md1               99M   24M   71M  26% /boot
none                 1014M     0 1014M   0% /dev/shm

So . . . I'm not sure what it (sme) decided to use on its own.  Appears to be raid 5'ish, but the numbers don't quite jive - 292-73=219 but I actually wound up with a 198g partition as shown above.

Whatever - the thing is WAY better than the previous machine that I was running off of
and I have lots more storage available that I did too.  ( my old "server" was an old circa 2001 pc w/a single 30 gig ide drive and 256m ram . . .   )  That old thing ran quite well for quite a few years though... 

the difference between the theorycal space and the physical one depends on:
- swap partition (double size of RAM)
- root's reserved space on FS (about 5%)..

as far as I understand you are using a IBM server with 73GB scsi 15k hd.. why did you choose to use SME's sw raid? I normally use sw raid if I don't have a REAL hw raid controller.. but ServRAID Card is worth to be used IMHO

Ciao

[smeghead]

I have quite a few DL380 G3's used for SME, work great & should be the last server the clients needs for SME until the hardware dies.

Use the 2 spare slots you have to add a one or two 36GB drives as spares for backups (assuming your backup is small enough for this space to be usable).  Once setup on the RAID controller I add them to SME but don't use LVM to make them somewhat more portable to another server in case of failure.  Most of the info you need to do this is in the wiki.

Setup one of the backup apps to use the drives & it flys.

I even have a mate that has his server colocated with a new 300GB drive for backup so he doesn't need any more rackspace & can get about 5 backups to fit on the 1 drive.

[Stefano]

Use the 2 spare slots you have to add a one or two 36GB drives as spares for backups

making backups on hd on the SAME hw is not a wise idea.. if something goes wrong you'd loose your live data and your backup

backup should always be done on external/removable/remote media

my 2c

[smeghead]

While I understand why Stefano says what he does the setups I use have a split hotswap backplane on seperate RAID controllers; there is no simple or cost effective way to backup the amount of data I need to other than using this methodolgy.

I also run a manual backup to external HDD's on some servers when any major changes occur.

In a perfect world I'd have a NAS in another datacentre with a 10GB backbone connection, alas not to be.

[Stefano]

there is no simple or cost effective way to backup the amount of data I need to other than using this methodolgy.

well.. I'm pretty sure that a used LTO scsi tape will not cost a lot.. I am sure that your data are worth more than 500 €

all IMVHO

[janet]

smeghead

... there is no simple or cost effective way to backup the amount of data I need to....

You don't say how much data, but a 1Tb external USB drive is only AUD$150, which used in conjunction with the default dar full/daily incremental backup or even the rdiff backup contrib, will do a good job of onsite backup (using hardware physically seperate to the server).

Also for next to no cost (except additional drive capacity if necessary), the Affa backup contrib can be installed on any existing remotely located web connected sme server, and be configured to backup any other sme server (or even multiple servers), thus creating a very easy to configure and virtually no effort to maintain, remote offsite backup system. Affa will do an initial full backup and then daily incrementals, so the daily data transfer cost is kept to a minimum. On broadband connections with generous or "unlimited" data allowances for a fixed monthly plan $ cost, using Affa is very inexpensive to run.

[smeghead]

.. on some servers 30-40GB of only moderately compressible data; with servers in a datacentre access is limited/restricted & rackspace costly.  I always do full backups, I have found incrementals to be problematic due to various reasons over the years.  With the size of some of the datafiles on some servers even incremental backups may not be that small.

The spare HS drive(s) in the chassis hasn't failed me yet in over 20 years, tho I've only needed to run a restore a handful of times due to using good, reliable, high end servers that are severely 'burned in' before deployment & well maintained afterwards.

It works for me in my situation.

Nuff said.