1. Concatenation? That's the same thing as striping, and there is no
such official RAID level called concatenation. The correct designations
of RAID levels are:
list of 5 items
• RAID 0 (Disk striping): RAID 0 splits data across any number of disks
allowing higher data throughput. ... (Sounds like concatenation, doesn't
it?)
• RAID 1 (Disk Mirroring): ... Replicates or "shadows" volumes for
failover protection; if one disk fails, the volume remains intact and
accessible.
• RAID 5 (Striping with parity): ...
• RAID 6 (Striping with double parity): ...
• RAID 10 (Striping + Mirroring):
list end
"Raid 10" is a misnomer. Its proper notation is RAID 1+0--mirroring plus
striping.
2. RAID 5 and 6 are not a simple concatenation of disk space, like
striping is. A RAID 5 set consists of a minimum of three disks, one of
which does not contain any usable data. It is the disk that contains the
checksum information to recreate data in the event that any disk in the
set is lost or damaged. Therefore, the size of a RAID 5 set is equal to
the value (n minus 1) times the size of the smallest disk in the set.
RAID 6 is the same as RAID 5, but with an additional checksum disk,
giving extra redundancy and protection in case of failure. Synology is
famous for using RAID 6, although they call their version something
else, and if I remember correctly, they say it is not compatible with
what most would call true RAID 6.
3. Striping (RAID level 0) is the most dangerous kind of RAID
arrangement on which to rely totally because if you lose one disk, you
lose it all. If I were you, I'd seriously rethink that stripe set of yours.
4. Don't combine striping and mirroring. It's inefficient, and could
cost you if you do it the wrong way. Plus, whether it's a mirrored
stripe set or a striped mirror, you're getting the space from only half
the disks used. Choose RAID 5 instead; then you'll be getting the disk
space from n-minus-1 times the size of the smallest disk (see above),
and you can always add more, one at a time, unlike a mirrored stripe or
striped mirror, where you'll have to add two disks at a time.
HTH
On 12/16/2018 1:28 PM, Eric Oyen wrote:
Well, I have found that to keep the prices down (IOW, keep your wallet
from going nuclear), it would probably be best to get several of the
smaller drives (like 4TB) and then raid them together . This will not
only allow you a larger filesystem, but also increased performance.
Striping raid is best for performance, while mirroring allows for
complete redundant backup with a CRC failover. I have several 3 TB
externals. Here all in raid 1 (striping), which gives me an effective
12 TB external with the max performance bandwidth that USB 3 can
provide (it’s not as fast as the 3GPS SATA drives, but it’s more than
fast enough).
Now, there are three methods of raid you need to be aware of (2 of
which I just mentioned):
1. Striping
2. Mirroring
3. Concatenation
The third one above simply allows you to append 1 drive to another.
This is also the easiest method to use if you simply want to add more
drives to the raid. It doesn’t have the performance of striping or the
redundancy of mirroring, but as a simple large drive, it works ok.
Basically, it’s up to you what you want to use. Just bear in mind,
none of the above solutions is for the newbie. A bit of reading will
be required.
-Eric
On Dec 16, 2018, at 2:49 AM, Ramy Moustafa <ramy.moustaf...@gmail.com
<mailto:ramy.moustaf...@gmail.com>> wrote:
Aha i understand now.
but all my external HDs will be more than 4 TB, and i will not be
able to buy 8 TB HD.
All my data now are 8 TB storage, so, must i buy 16 TB hard drive?
so, what will be teh 2nd solution?
On Dec 14, 2018, at 4:31 PM, 'Tim Kilburn' via MacVisionaries
<macvisionaries@googlegroups.com
<mailto:macvisionaries@googlegroups.com>> wrote:
Hi,
No, it can be just one backup volume. First limitation is that the
backup volume should be about twice as big as the data being stored.
So, if you have less than 2 TB of data that needs backed up, then a
4 TB Time Machine backup volume is perfect. If the total is greater
than that, you might be fine, but the backup may run out of space
too quickly. All that out of the way, you just go into your Time
Machine pane in System Prefs, press the Options button and make sure
that none of your external drives are excluded from the backup.
Essentially, that's all you need to do. Leave all drives connected
all the time and let Time Machine do its thing automatically. Note
that the first backup may take days as the data is being prepared
for and backed up to the new drive. All subsequent backups should
be much faster.
Later...
Tim Kilburn
Apple Teacher
(with Swift Playgrounds Recognition)
Fort McMurray, AB Canada
On Dec 14, 2018, at 06:32, Ramy Moustafa <ramy.moustaf...@gmail.com
<mailto:ramy.moustaf...@gmail.com>> wrote:
My friends:
I finally got 4 tb hard disk, that i plan to use it for weekly backup,
I have more than 3 hard disks that i hope to backup them on this hd,
so, must i divide this new hd to 3 volumes to use time machines?
or what is the best thing?
Thanks for helping.Ramy moustafa saber
licturer at:
faculty of musical education
music arranger and sound engineer
Sent from my iPhone
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