Three-way mirror disk requirement

In Windows 2012 Storage Space, why 3-way mirror requires minimum 5 disks instead of 3? How does 3 way mirror works? I tried to find the tech paper on MS website but either I didn't try hard enough or the info is not there.

Hi,
The reason is that a 3-way mirror uses a quorum. In order to keep running, the mirror space must keep over 50% of the disks functioning. So a 3-way mirror must have at least 5 physical disks to be able to survive the loss of up to 2 physical disks.
For more detailed information, please refer to the links belwo:
Tip Of the Day: 3-way Mirrors
http://blogs.technet.com/b/tip_of_the_day/archive/2013/08/29/tip-of-the-day-3-way-mirrors.aspx
mirror in storage pool
http://social.technet.microsoft.com/Forums/windowsserver/en-US/2e6955b7-b293-4880-8fb3-8b4ce0e02ec9/mirror-in-storage-pool?forum=winserver8gen
You could also refer to the article below to know more about three-way mirror:
Windows Server 2012 SMB 3.0 File Shares: An Overview
http://www.petri.co.il/windows-server-2012-smb-3-file-shares.htm
Please Note: Since the website is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.
Regards,
Mandy
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Similar Messages

How to calculate the disk failure level for a 3-way mirror pool?

On another post in this forum, the following information regarding a 3-way mirroring storage pool is given:
Pool requires a quorum of 50% plus drives to be present to survive.
with 3 way mirror - we have a guarantee of surviving 2 disk failure.
Maintaining the above requirements and providing the guarantee -
mandates us to have minimum 5 disks in pool. As if we loose 2, we still
have 3 in the pool (>50%) for pool to maintain it's quorum.
Just to be sure, I would like Microsoft to confirm that the following calculation applies to any number of disks in a 3-way mirroring pool.
If the number of disks in a 3-way mirroring pool is n, INT(n/2) disks can fail without data loss.
Examples:
With 5 disks, INT(5/2)=INT(2.5)=2 disks can fail.
With 6 disks, INT(6/2)=INT(3)=3 disks can fail.
With 9 disks, INT(9/2)=INT(4.5)=4 disks can fail.
Am I right in this assumption?
Thanks for your answer.

Hi,
>>Am I right in this assumption?
Based on my understanding, it’s not this case.
Mirror spaces are designed for increased performance and protect your files from drive failure by keeping more than one copy. Two-way mirror spaces make two copies of your
files and can tolerate one drive failure, while three-way mirror spaces can tolerate two drive failures.
Regarding this point, the following thread can be referred to for better understanding.
Storage Spaces - Disk resiliency
http://social.technet.microsoft.com/Forums/en-US/8f13ecf3-61c8-4505-90da-e8a01023c62d/storage-spaces-disk-resiliency?forum=winserverfiles
In addition, regarding storage spaces, the following article can be referred to for more information.
Storage Spaces Overview
http://social.technet.microsoft.com/wiki/contents/articles/15198.storage-spaces-overview.aspx
Best regards,
Frank Shen

2 / 3 way mirror - any visible difference ?

Hi - I created some 2 & 3-way mirrored storage spaces (on Win2012R2)
(Luckily, when I created them I used "sensible" names, so I know which is 2-way and which is 3-way)
But since then, I've been up&down Server Manager's menus, but I can't see anywhere where Server Manager shows if it's a 2 or 3-way mirror
Have I missed something, or do I have to resort to PowerShell to display this information ?

Hi,
In the Server Manager, you could right click the virtual disk, click Properties, then click
Details, in the Property drop-down box choose NumberOfDataCopies. The value 2 indicates two-way mirror and the value 3 indicates three-way mirror. You could also use the PowerShell command “get-virtualdisk –friendlyname <friendly
name> | fl” to get the value of NumberOfDataCopies.
Best Regards,
Mandy
Please remember to mark the replies as answers if they help and unmark them if they provide no help. If you have feedback for TechNet Subscriber Support, contact [email protected]

Clustered Storage Spaces - 3 disk minimum for 2-way mirror?

Why will a 2 disk, 1 column, 2-way mirrored space work fine outside of a cluster? Yet, when I want to use clustered storage spaces I need a minimum of 3 physical disks for a 2-way mirrored space? Killing me...
I mean if I add 2 additional disks and do a 4 disk, 2 column, 2-way mirrored space it's ok. What would be the purpose of using 3 disks as a minimum?
Thanks,
Scott

Hi,
Could you please give us more detailed explanation to help us understand your question?
“Cluster storage space” did you mean “Cluster Share Volume” for Hyper-V Cluster?
What did you mean “mirrored space”, did you mean software mirrored volume? For a cluster, we recommend you use a shared storage and configure disk fault tolerance with hardware RAID.
Give us more information of your questions for further troubleshooting.
For more information please refer to following MS articles:
Mirrored Volumes
http://technet.microsoft.com/en-us/library/cc938487.aspx
How to Configure a Clustered Storage Space in Windows Server 2012
http://blogs.msdn.com/b/clustering/archive/2012/06/02/10314262.aspx
Understanding Requirements for Failover Clusters
http://technet.microsoft.com/en-us/library/cc771404.aspx
Hope this helps!
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Question for GR IR functionality - audit requirement (three-way) match

Hello,
I have a question in regards to three way match functionality in SAP (matching of PO, GR and IR). Auditors asked us if GR-IV indicator is checked for every PO, and for our company this indicator cannot be checked for every PO due to drop shipments, LC terms, etc. However, AP is ensuring that GR document is posted prior to posting IR for all POs. In this case, even though GR-IV indicator is not checked at PO item level, does SAP enforce automatic three way matching based on the tolerance key set (DQ and PP), or does SAP not perform three way match since the GR-IV indicator was not set in the first place?
Please share some insight. Thank you.

Hi,
As you know three ways match related to PO-GR-IV but in your case you want pay drop shipments and LC terms to vendor where you need two way match which is with PO-IV. The disadvantage in two way match, you never know whether the whole PO amount is delivered or not in your system (in real scenario). For two way match, select those vendors in t.code:XK02 and do not select check box of “GR-Based Inv. Verif.” in Control data segment in Purchasing data view & then save.
Now create a new PO and go for directly invoice verification WRT new PO.
For more refer threeway match details
SAP Threeway Match Functionality & configuration
Regards,
Biju K

2 Way mirror via Storage Spaces using 2xJBODS

Looking to setup 2xJBODS connected to a cluster File Servers & use 2-WAY mirror for the pool. Its clear that w. a 2way mirror that it can only handle 2 drives failing before seeing data loss but is that 2 drives between both JBODS or is that 2 driver
per JBOD? Also I know that if 1 JBOD were to completely go offline that I would need a total of 3 JBODS in order for vms,etc to not be affected but what is the expected behavior. A jbod goes offline and we lose vms but data is not loss? Once the jbod
comes back data will be back to normal?

if you are going to mirror the 2 of them yes
What are the resiliency levels provided by Enclosure Awareness?
Storage Space Configuration
All Configurations are enclosure aware
Enclosure or JBOD Count / Failure Coverage
Two JBOD
Three JBOD
Four JBOD
2-way Mirror
1 Disk
1 Enclosure
1 Enclosure
3-way Mirror
2 disk
1 Enclosure + 1 Disk
1 Enclosure + 1 Disk
Dual Parity
2 disk
2 disk
1 Enclosure + 1 Disk
REF: Storage Spaces Frequently Asked Questions (FAQ)
Storage Spaces, JBODs, and Failover Clustering – A Recipe for Cost-Effective,
Highly Available Storage
This post is provided AS IS with no warranties or guarantees, and confers no rights.
~~~
Questo post non fornisce garanzie e non conferisce diritti

Allocation of space for 3-Way Mirror

A picture paints a thousand words, so I painted. Far easier than tying myself up in knots of words.
Many thanks.

Hi,
A1: 450GB is correct.
A2: The 2 disks requirement is not static. See the explanation in following article, that why it needs 5 disks for a 3-way mirror:
http://blogs.technet.com/b/tip_of_the_day/archive/2013/08/29/tip-of-the-day-3-way-mirrors.aspx
The reason is that a 3-way mirror uses a quorum. In order to keep running, the mirror space must keep over 50% of the disks functioning. So a 3-way mirror must have at least 5 physical disks to be able to survive the loss of up to 2 physical
disks.
Below is my personal view: With 9 disks act as 3-way mirror, we could lost 6 disks in maximum. As it must keep over 50% of disks in running, we need more than 4.5 disks which is 5, so we need 2 more disks.
Please remember to mark the replies as answers if they help and un-mark them if they provide no help. If you have feedback for TechNet Support, contact [email protected]
Thanks for this, Shaon Shan.
When it comes to a 3-way mirror, is a better way of calculating the total amount of enclosure storage for the desired amount of usable storage, to multiply your desired usable storage by a factor of 5?
So, if using 500GB drives, to have 1TB of usable storage from a 3-way mirrored virtual disk, I would need to have 5TB of total storage, so a complete total of 10 drives?

Three-Way Pegging

Please explain me what is Three-Way Pegging ?

Three-Way Pegging is used to plan and schedule bulk shipments based on supply and demand information. The term three-way refers to demand items (stock requirements or customer requests), supply avails (what is produced, purchased, or in stock), and transportation avails (vehicles, vessels, or pipelines available to complete the shipment).
The term pegging refers to the matching of demand items to supply avails and transportation avails for the purpose of scheduling of bulk shipments, such as marine voyages or pipeline batches. You plan and schedule bulk shipments, by assigning the pegged items to the Distribution Schedule in Three-Way Pegging. From the Distribution Schedule you can create carrier nominations, as well as continuously update the schedule.

Booting from a mirrored disk on a zfs root system

Hi all,
I am a newbee here.
I have a zfs root system with mirrored disks c0t0d0s0 and c1t0d0s0, grub has been installed on c0t0d0s0 and OS booting is just fine.
Now the question is if I want to boot the OS from the mirrored disk c1t0d0s0, how can I achieve that.
OS is solaris 10 update 7.
I installed the grub to c1t0d0s0 and assume menu.lst need to be changed (but i don't know how), somehow no luck.
# zpool status zfsroot
pool: zfsroot
state: ONLINE
scrub: none requested
config:
NAME STATE READ WRITE CKSUM
zfsroot ONLINE 0 0 0
mirror ONLINE 0 0 0
c1t0d0s0 ONLINE 0 0 0
c0t0d0s0 ONLINE 0 0 0
# bootadm list-menu
The location for the active GRUB menu is: /zfsroot/boot/grub/menu.lst
default 0
timeout 10
0 s10u6-zfs
1 s10u6-zfs failsafe
# tail /zfsroot/boot/grub/menu.lst
title s10u6-zfs
findroot (BE_s10u6-zfs,0,a)
bootfs zfsroot/ROOT/s10u6-zfs
kernel$ /platform/i86pc/multiboot -B $ZFS-BOOTFS
module /platform/i86pc/boot_archive
title s10u6-zfs failsafe
findroot (BE_s10u6-zfs,0,a)
bootfs zfsroot/ROOT/s10u6-zfs
kernel /boot/multiboot kernel/unix -s -B console=ttya
module /boot/x86.miniroot-safe
Appreciate anyone can provide some tips.
Thanks.
Mizuki

This is what I have in my notes.... not sure if I wrote them or not. This is a sparc example as well. I believe on my x86 I still have to tell the bios to boot the mirror.
After attaching mirror (if the mirror was not present during the initial install) you need to fix the boot block.
#installboot -F zfs /usr/platform/`uname -i`/lib/fs/zfs/bootblk /dev/rdsk/c0t1d0s0
If the primary then fails you need to set the obp to the mirror:
ok>boot disk1
for example
Apparently there is a way to set the obp to search for a bootable disk automatically.
Good notes on all kinds of zfs and boot issues here:
http://www.solarisinternals.com/wiki/index.php/ZFS_Troubleshooting_Guide#ZFS_Boot_Issues

Though the root disk is mirrored, server is unable to boot from alternate disk (mirror disk)

Hi PPl,
It happened second time in a row. Though the root disk is mirrored, server is unable to boot from alternate disk (mirror disk)
When the disk was found faulty, still unable to boot the OS from alternate disk, it says it still probe/look for other disk
Here are the console log when I tried to boot the OS
sc> console
Enter #. to return to ALOM.
WARNING: /pci@0/pci@0/pci@2/scsi@0 (mpt0):
Disconnected command timeout for Target 1
WARNING: /pci@0/pci@0/pci@2/scsi@0 (mpt0):
Disconnected command timeout for Target 1
WARNING: /pci@0/pci@0/pci@2/scsi@0 (mpt0):
Disconnected command timeout for Target 1
In such condition left out with only two options.
1) Remove the faulty disk physically and boot
(or)
2) Replace the faulty disk and boot it
Any way, I can disable the faulty disk in BIOS (or) booting from cd-rom and do something to avoid it?

You can't boot from systems earlier than that shipped with the computer. For example, early 2008 Mac Pros come with 10.5.1 and can't boot 10.5
Also you can't boot with a DVD that was shipped with a different model Mac.

Can I do a three-way conversation on iMessage or FaceTime?

I'm using an iPad 2, I want to to do a three-way with my friend and her sister. They're both using iPhone 4S. All Running iOS 5, obviously...
Even if there's any applications that someone knows of we could install, please answer. Thanks!

Hi Teach,
Unfortunately conference calls are not an application that Facetime supports. In my opinion, it would probably not work very well with personal Lan networks because it would require too much bandwidth, since streaming video does require quite a bit of it. So for now, it has to be one on one.
Wuz

Three way matching: the ultimate solution

All,
I've been looking for the ultimate solution and answer with regard to three way matching and how to make sure that it is always in place.
Up to now I used to rely on the GR based IV flag in the PO in combination with tolerance limits and MRBR for MIRO.
Lately the option if the GR and the IR indicator in the PO popped up but this leaves me with a couple of questions:
How do we know for sure that the goods receipt are always linked to the PO? (otherwise this will leave me a bunch of invoices I won't be paying)
How do we know for sure that all the invoices are linked to the PO? (Since MIRO provides me other options as well)
How do I know for sure that the invoice are blocked based on the right propositions? (I guess the tolerance limits but I really want to be sure this time)
How do I know for sure that the unblocking is done timely and is valid?
What's the impact of the document types in this story and how can I manage these best?
What it basically comes down to is that I'm more than happy to believe that setting the GR and the IR indicator in the PO is sufficient in combination with tolerance limits but I would appreciate it when somebody is able to talk me through the three way matching logic in SAP and the configuration impact.
Hopefully somebody can help me out.
Regs,
Paul

With regards to GR, if you are doing a 101 movement type Goods Receipt, it requires either a PO or a Production order to receive against. Receipts without a PO, 501's, 561's,etc should be restricted in the system. In most SAP implementations, the receiving department can usually just use the 101 (receipt against a PO) or a 102 (reversal) and 122 (return to vendor). So you should be pretty secure the receipts (if being done) are done against a PO.
I do not remember the table, but there was a table (at least in 4.7) that restricted the ability to do 2-way match (not allowed). You can also set the fields on the PO as required "GR-based IV"(WEBRE) and "IR Required" (REPOS field) to make sure it is required to have an IR and GR-based IV. GR Required indicator (WEBRE) should also be required if 3-way is ALWAYS happening.
I hope this helps?

Mirroring Disk Drive Question. Using SVM for Disk Mirroring.

Hello,
I am trying to do mirror in solaris 9 using Solaris Volume Manager. I have total 0-7 disks
4 5 6 7
0 1 2 3
Drive 0 and Drive 4 = Boot Drives
Need to Mirror following drives.
Drive 1 and Drive 5 = Need to mirror
Drive 1 was mounted on: /prod1, /prod2, /prod3, /prod4, /prod5.
Drive 5 was mounted on:/prod16-----/prod20
Then i have umounted both drives and then using format command to equalize the parititions.
Then
I have done following steps.
metadb -a -f /dev/dsk/c1t1d0s7
metadb -a -f /dev/dsk/c1t5d0s7
2)
metainit -f d100 1 1 c1t1d0s0
metainit -f d101 1 1 c1t5d0s0
metainit d0 -m d100
metattach d0 d101
3)
# newfs /dev/md/rdsk/d0
newfs: /dev/md/rdsk/d0 last mounted as /prod16
newfs: construct a new file system /dev/md/rdsk/d0: (y/n)? y
4)
# mount -F ufs /dev/md/dsk/d0 /prod16
Now, target 5 is submirror with target 1 mirror. I was wanted to do /prod1 but some reason it showing /prod16. How can i change this to /prod1?
OR
2nd question: do i need to mirror each drive vice verse?
for example:
metainit -f d102 1 1 c1t5d0s0
metainit -f d103 1 1 c1t1d0s0
metainit d1 -m d102
metattach d1 d103
Let me know.
Thanks
Adeel

I do it a little differently, as follows, which I gleaned from http://slacksite.com/solaris/disksuite/disksuite.html
Create state replicas on slices 6 & 7 (any could be used but we usually use 6/7)
metadb -a -f /dev/dsk/c1t0d0s6
metadb -a /dev/dsk/c1t0d0s7
metadb -a -f /dev/dsk/c1t1d0s6
metadb -a /dev/dsk/c1t1d0s7
Initialize submirrors for root slice 0 on both drives, and create one-way mirror between metadevice d0 & first sub-mirror
metainit -f d10 1 1 c1t1d0s0
metainit -f d20 1 1 c1t1d0s0
metainit d0 -m d10
update root entry in /etc/vfstab
metaroot d0
Initialize submirrors for swap slice on both drives, and create one-way mirror between metadevice d1 & first sub-mirror
metainit -f d11 1 1 c1t0d0s1
metainit -f d21 1 1 c1t1d0s1
metainit d1 -m d11
Initialize submirrors for /var slice5 on both drives, and create one-way mirror between metadevice d5 & first sub-mirror.
metainit -f d15 1 1 c1t0d0s5
metainit -f d20 1 1 c1t1d0s5
metainit d5 -m d15
Edit /etc/vfstab
add these lines to /etc/vfstab
/dev/md/dsk/d1 - - swap - no -
/dev/md/dsk/d5 /dev/md/rdsk/d5 /var ufs 1 no logging
REBOOT server
Attach second half of mirrors to allow two drives to synchronize
metattach d0 d20
metattach d1 d21
metattach d2 d25
I hope this helps.
Stephanie

Disable the conference call/ three-way calling function

I have a BlackBerry Bold 9930 - NEED HELP - Is there any way to disable the conference call/ three-way calling function on this phone???? I can't make a normal phone call without randomly starting a three-way call with someone from my contact list or recent call log. I can only keep the phone so far away from my ear!!!! Please help this is a real problem!

Does ‘DM’ mean ‘direct message’ like this email or do I need to send this email somewhere else to reach ‘BobbyS_VZW’. Would like to know before I send my billing password & phone number.
Thank you,
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Message was edited by: Admin Moderator

Three-Way Match

We currently use three-way match as a standard AP process. A recent change has required a number of suppliers to be paid before actual goods receipt.
What is the best practice for the scenario where invoice needs to be paid ahead of physical goods receipt?
Can configuration be done to have match compare inbound delivery instead of goods receipt?
Regards,
JG

Hi Jeff,
SAP also has a prepayment process. Here are links to the SAP Help information on this process.
[PrePayment|http://help.sap.com/erp2005_ehp_04/helpdata/EN/29/6eec40a600e015e10000000a114b1d/frameset.htm]
[Entering Invoices|http://help.sap.com/erp2005_ehp_04/helpdata/EN/29/6eec40a600e015e10000000a114b1d/content.htm]
[Posting Prepaid Logistics Invoices|http://help.sap.com/erp2005_ehp_04/helpdata/EN/29/6eec40a600e015e10000000a114b1d/frameset.htm]
In the off chance you sometime do not plan to enter goods receipts or the order document would be considered a "blanket" type order, you could always use the standard functionality of Framework Orders (FO purchase order type) which only expect invoices.
SDN Link:[Framework Order|Framework Order]
Regards

Three-way mirror disk requirement

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