RAID 0, RAID 1, RAID 5, RAID 1+0 explained

RAID stands for Redundant Array of Independent Disks, originally known for Redundant Array of Inexpensive Disks.

Most commonly used RAID levels:

RAID 0

RAID 1

RAID 5

RAID 10 (also known as RAID 1+0)

In all the explanation below:

• A, B, C, D, E, F - represents blocks.
• p1, p2, p3 - represents parity.
• Parity - an error protection scheme which is a widely used method in information technology to provide fault tolerance in a given set of data.
• Strip - chunks of data are spread across multiple arrays, possibly all the drives in the system.

RAID LEVEL 0

RAID 0 – Blocks striped. No Mirror. No Parity.

Key points:

• Minimum 2 disks.
• Excellent performance ( as blocks are striped ).
• No redundancy ( no mirror, no parity ).
• not recommended to be used with critical systems.

RAID Level 1

RAID 1 – Blocks Mirrored. No Stripe. No Parity.

Key points:

• Minimum 2 disks.
• Good performance (no striping. no parity).
• Excellent redundancy (as blocks are mirrored).

RAID Level 5

RAID 5 – Blocks Striped. Distributed Parity.

Key points:

• Minimum 3 disks.
• Good performance ( as blocks are striped ).
• Good redundancy ( distributed parity ).
• Best cost effective option providing both performance and redundancy. Use this for DB that is heavily read oriented. Write operations will be slow.

RAID Level 10

RAID 10 – Blocks Mirrored. Blocks Striped.

Key points:

• Minimum 4 disks
• Also called "stripe of mirrors"
• Excellent redundancy ( as blocks are mirrored )
• Excellent performance ( as blocks are striped )
• If you can afford the dollar, this is the BEST option for any mission critical applications (especially databases).

Detailed explanation on RAID levels @ http://en.wikipedia.org/wiki/Standard_RAID_levels

VMWARE VMDK to HyperV VHD

wonderful free converter to switch from vmware storage to hyperv storage.

I could convert vmware machines (server 2008 R2/ SQL 2008 R2) to hyperV machines using 2Tware convert software without any hassles. After the hard-disk conversion, bring the machine online for which the process of attaching the vhd file remains same.

NAS

reliable backup storage

NAS - network attached storage - reliable backup storage

I inherited a couple Netgear ReadyNAS boxes 3 years ago and certainly do not regret purchasing the network attached storage. Coz. price fits within budget, lot of functionalities, centralized backups, data redundancy (go with RAID or not its up to customer), ease to use and performance is great.

By RAID5 approach we could get only 1.4T of 500GBx4. I would rather prefer 1.5Tx4 and align storage schedule in 4 drives separately. So Sun to Wed storage schedule from disk 1 to 4. In the event of a disk failure we can rely on other 3 disks.

OR RAID0 configuration - 1.5Tx4 with 2 volumes of 3T=3Tx2. This way storage schedule can be pointed to two volumes relying on 3Tera redundancy. If RAID5 with 1Tx4 we could get only 2Tera approx and a redundancy of 4 disk which is actually not required in terms of a network storage.

Here I opted RAID0 as we have a separate storage share where backups are stored. So even if 1 drive fails i can still rely on the other storage share.

I have used ReadyNAS NV+ second box with RAID5 config where all critical storage happens and from there the data is collected to tape

Netgear ReadyNAS FAQ http://www.readynas.com/kb/home

check for updates on your computer to resist vulnerable attacks

Microsoft has released recent correction in update codes prompting you to install new windows update software. Windows update message: "Install new windows update software".

Make sure updates are tested and deployed on all systems regularly by 2nd week of every month.

refer why to secure your system?

Window Error on Updates: resolved

common window update error which eventually ends in frustration..

code 8024402F

Resolution:

i) reset internet explorer settings to their default conditions. Tools >> internet options >> Advanced Tab >> Reset >> make sure delete personal settings check box is selected >> Reset.

ii) check for updates now. If persists,

login with local admin and proceed.

With admin login the updates went through perfectly without any traces of pending updates.

Emails Sent by Users Stuck in Outbox/Draft Folder - Exchange 2007

Make sure that the Anti-Virus Exclusion lists are enabled on ePO enterprise server level  (Antivirus Management level) as per the recommended Microsoft article-

Directory Exclusion lists for Exchange (exchange 2007)

PickupDirectoryPath:

C:\Program Files\Microsoft\Exchange Server\TransportRoles\Pickup

ReplayDirectoryPath:

C:\Program Files\Microsoft\Exchange Server\TransportRoles\Replay

RootDropDirectoryPath:

C:\Program Files\Microsoft\Exchange Server\TransportRoles\data\Queue

C:\Program Files\Microsoft\Exchange Server\TransportRoles\data\IpFilter

C:\Program Files\Microsoft\Exchange Server\Working\OleConverter

C:\WINDOWS\system32\inetsrv

C:\Program Files\Microsoft\Exchange Server\ClientAccess

Process Exclusions and File Name Extension Exclusions

Refer Microsoft recommended Article at: http://technet.microsoft.com/en-us/library/bb332342(EXCHG.80).aspx

Refer managing McAfee Anti-Virus file and folder exclusion at https://kc.mcafee.com/corporate/index?page=content&id=KB50998&pmv=print