Disk Mirroring and Disk Striping W/ Parity at same time - Bad on HD??

[Pinkman]

We have a client that wanted to have fault tolerance on thier boot\system partition along with there data.&nbsp;&nbsp;They have 3-8 gig SCSI HDs.&nbsp;&nbsp;I mirrored the boot/system partition, then created a stripe set with parity on the remaining free space on the three disks.<br><br>Everything works fine, but the disk I/O is going crazy.&nbsp;&nbsp;It is writing all the time - even when the server is idle.&nbsp;&nbsp;Is a huge amount of write activity normal on this type of set up?<br><br>If this is normal - what is the life of a HD with this type of I/O constantly being written to it?<br><br>Any tips would be great.<br><br>Thanks,<br>Pinkman MCP

 

[MrGeek]

Hmm not to be doubting you, but could you explain how you did all that on 3 drives?&nbsp;&nbsp;I mean give me the whole setup info!! <p>The Geek<br><a href=mailto: > </a><br><a href= > </a><br>Dont be afraid to share what you know. There are no losers in our arena, only self rightous monkeys atop their own tree.

 

[SRaji]

Hi,<br><br>Surely you will not have any problem. Dont doubt your hard disk life.<br><br>Regards,<br>Rajalakshmi. MCSE<br><A HREF="mailto:dassraji@hotmail.com">dassraji@hotmail.com</A>

 

[Pinkman]

MrGeek . . .<br><br>First I created the Mirror of the boot/system partition.  It was only about 1.0 gig worth of information.  It was created on C and D which are two HD's on seperate controller cards.<br><br>With the remaining room from C D and E (again all on seperate controller cards) - I created the RAID 5 with parity.  Pretty simple really.  I had to make sure that I deleted any extended partitions affiliated with the disks so I could utilize the maximum data store space.  Each drive was 8 gig . . . after creating the mirror, I ended up with about 15 gig of data space that is protected by the RAID 5 with parity.<br><br>SRaji . . .<br><br>Thanks for the optimism!  I am hoping the same thing! <br><br>Thanks for the posts . . . <br>Pinkman

 

[cadman2]

Perhaps managing the swapfile size would minimize some IO activity...setting the max and min size the same.<br><br>John Payne <p> <br><a href=mailto: > </a><br><a href= > </a><br>

 

[ATCal]

Are you also mirroring the swap file? You should have some room left on the third drive (1 gig mirror on two drives should leave you a gig on the third). I would create my swapfile there as it does not require any redundancy. <p>Al<br><a href=mailto: atc-computing@home.com> atc-computing@home.com</a><br><a href= > </a><br>

 

[RichardMoran]

Surely, your explaination of your drive setup clearly illustrates the reason for high activity, if I've understood you correctly.<br><br>If you have mirrored your boot/system partition using drives C & D, every write access to the original partitition is duplicated on the mirrored partion. This will include temporary files, swap files, etc...<br><br>This means that the physical drives C & D are quite active.<br><br>You then have created a RAID 5 partition using the space left on C,D, & E. Any writes to this partition will be striped across all 3 drives, even though C & D, are already being used for the mirror set.<br><br>With the exception of the E drive, your drives are being fairly hammered.<br><br>I would install another two drives to enable the mirror set, and RAID array, to exist on seperate physical drives. Not only would this solve the activity issue, it would also improve the performance.<br><br>Rik<br><br>

 

[fenris]

I have a qestion regarding the mirroring and strip set being used on the same machine, isn't that a bit of overkill? Or is it just an added level of redundancy?<br><br><br> <p>Troy Williams B.Eng.<br><a href=mailto:fenris@hotmail.com>fenris@hotmail.com</a><br><a href= > </a><br>

 

[RichardMoran]

fenris,<br><br>My understanding ( which may be completely wrong! ) is this.<br><br>If you are using a hardware RAID solution, you can just have the whole of NT, or any other operating system, striped across all of the disks, if that's what you want.<br><br>If however, you are using NT's built in fault tolerance ( software based ), it is a different matter.<br><br>I believe that to get fault tolerance on your system/boot partition you cannot have it as part of a striped set, but instead you have to include it in a separate mirrored set.<br><br>My guess would be that NT cannot read the striped set, until it has been able to load the relevant code from the Operating System.<br><br>This would make it impossible to boot from a striped set on it's own! <br><br>Additionally, if the C drive failed, you wouldn't be able to reconstruct the drive from the striped set, as you would no longer be unable to load the OS.<br><br>Therefore, you would definitely need the system/boot partition on a separate disk.<br><br>I hope this makes sense.<br><br>Rik<br><br>p.s. If my understanding is wrong, I would welcome any comments.

 

[fenris]

If I understand this correctly, you are running NT off of c: and have it mirrored. Everything else, except NT,is on the raid. If this is the case then it makes sense.<br><br>Where I am now we just use mirrored drives because all the data we use fits on a 9Gb drive. That is why I was confused. But I will have to remember that for the future.<br><br>Thanks for the explaination. <p>Troy Williams B.Eng.<br><a href=mailto:fenris@hotmail.com>fenris@hotmail.com</a><br><a href= > </a><br>

 

[MasterRacker]

Rik,<br><br>Your description makes sense to me.&nbsp;&nbsp;I would also recommend using one pair of disks for the mirror and a completely different physical set of disks for the RAID. <p> Jeff<br><a href=mailto: masterracker@hotmail.com> masterracker@hotmail.com</a><br><a href= > </a><br>If everything seems to be going well: you don't have enough information.......

 

[ATCal]

One of my clients has a sever setup this way and in theory it looks good- however I would like to see someone crash a setup like this and recover before I would recommend it. If redundancy is that important an issue (I think so) why not spring for a hardware RAID card and have a bootable stripe set?

 

[fenris]

I was wondering about that myself, why not spring for the hardware. I found that windows works much better when it doesn't have to do anything Sometimes I find I get more worke done with it off ;-)

 

[ATCal]

Most good server boards with onboard SCSI like the Intel L440GX (found in many Branded servers) have a Raid Port on one of the PCI slots. Adaptec has a card called the ARO-1130U2 that snaps in without even removing a cable. Cost through distribution is @$250. It takes standard EDO Dimms for increased memory. Worth the price if you ask me.