Koozali.org formerly Contribs.org

hardware raid

carload

hardware raid
« on: June 21, 2004, 08:58:07 PM »
Hi,
anyone with experience implementing ATA hardware raid please email me if you are willing to answer a few questions.  
I posted a question on this to the general discussion board, a guest said he had success with 3ware ATA raid controller, but haven't been able to raise him again for followup..
Thanks.

berzek

3ware EIDE ATA - OK
« Reply #1 on: June 22, 2004, 12:51:06 AM »
hello,

here in italy/florence i used 2 models of 3ware with different versions of e-smith form the old 4.1.2 with a driverdisk (dd) durning boot time and then with ver5.5 and also with ver6.03beta. The models were the 74xx and 75xx series, the newer ones only superseed the old ones and should work right out of the box, but i cannot confirm that.

The latter versions have the module already into the kernel so you don't need to have the original dd.

here are 3 links to pdf files taken from a a running machine to give you an idea of what it looks like via the web based panel::
http://www.berzek.com/SCSI%20ID%200%20%203ware%207500%204LP%20ATA%20RAID%20Controller%20Configure%20page.pdf
http://www.berzek.com/SCSI%20ID%200%20%203ware%207500%204LP%20ATA%20RAID%20Controller%20Home%20page.pdf
http://www.berzek.com/Technical%20Detail%20View%20page.pdf

Important point with 3ware is their naming scheme , which is correct in a switch baseed configuration, so a 4 port card supports a MAX of only  4 disks In a switch conf, there is no master slave DMA switching/talking but a true logic transfer to the port hence 4p has max 4 disks and 8p ahs 8 disks and so on.

There is a nice web based controller program on port :1080 which satisfys my (tech admin) requirements, this way you can even port forward from putty to check in for remote administration. The series i used was the old 74xx and 75xx series of 64bit PCI 66MHz performance (bus side, not the O.S.) The LP cards are Low Profile ie: they have a mounting bracket supplied which allows you to change the slot height down to a 2U chasis (as the card is under 2U in height)  else a standard PC case mounting is available.

a good base configuration is with 4 disks where all disks should preferably be of the same batch, ie: p/n should be within the same series to have a minimum tolearance difference between them (not to be really taken care of unless you are a fanatic or the client itself !) also this way you would get all with the same firmware version (hopefully) Also here I will not comment on the choice of supplier/brand of disks as that is another ball game in the industry. rule of thumb is check how the warranty/gurantee is handled and how many years does the dealer give you and howmany years is it actually covered by the manufacturer ?

even better performance (speed and relability wise)is held in RAID 5 with more higher number of disks (increasing probability of failure) so in that case if you buy a 8port card use a nice balance of 6 disks in RAID5 and 2 disks for 2 spare units for automatic rebuilding, please note that the 2 spare disks are alwalys on and hence alwalys spinning so take proper calculations of power consumption on the ATX unit ! That also means that they are how spare and not Hot swappable unless you buy the correct hot swap cages that 3ware makes (a common misbelief on hot swapping)

On the fanatic side i instaled 5 2.5" 15GB disks (yes thats correct laptop portable disks with respective converters) on a 4 port 3ware card with a slightly decreased performance as compared to its equivalent in 3.5" disks , but the assumed (assumed ... because we still don't know these disks have only finished 3 years of service) risks are lower as laptop disk drives heat up less, are designed to take more rough handling and consume less power (consider that 3 years ago ATX units of 300W was server class !

well much of this has nothing to do with 3ware and e-smith but hardware raid incurs a more tactical approach not just stuffing the machine with disks, (remember, the more you you have the difficult it gets ! that goes for life too :)
----------------------------
the step below is at your own risk, and be warned that you risk  damadged disks, controller card, motherboard, ATX powersupply or a combination of these. It is not meant for a demonstration but to give an insight of one of the possible suitations in the life of a disk. So DO NOT do this step unless you are in an sponsered LAB.

Dangerous step starts here ::

   consider what steps you will take to rebuild a H/W disk failure in RAID 5 for example. A suggestion is build the machine and then check it's functionally by taking the power connector away from a working disk unit (stimulates a case of hardware failure like a disk crash, or motor drive currents rushing very high! or simple thunder storms on the ATX unit or a faulty connector or drive electronics gone faulty) if the controller card and drive is good nothing should burn, and the spare unit should automatically kick in to fill the simulated drive failure.

V.IMP::

 DO NOT put back the power connector to the drive, this way you migh still not have damadged the whole onetime test. continue instead by checking data integrity and check for sizes and also unmount the file system and check for missing inodes or bad file indexes. if the H/W implemented RAID subsystem is good then everything should work like clockwork, time to get back to a balanced RAID 5 should depend upon IO speed with the drives and disk capacity that was actually in use.
-----------------------------------

last point you must configure the card/disk units at BIOS time else there is no use of it and all disks will be seen seperately !

Sorry in if this post has bored you ! :hammer:

cheers,
.aniston

PS:: I do not work for 3ware nor am i in any way connected to them, neither do i resell 3ware  for them or against them, all findings are based on practical usage.

carload

hardware raid
« Reply #2 on: June 22, 2004, 02:00:00 AM »
Thank you, berzek, for all the good info!

Anyone else ?

Berzek, if you would be kind enough to email
me (carl at rhinehart-family.com) so I could
maybe ask you a question or two off line?
Thanks again!