And to be safe or double safe the best ones to use are: Raid 1 mirroring, That way if a disk dies you have a copy.
Raid 5, However I say minimum 5 disks that way if a disk dies you still have a functioning array if a second disk dies then your in a state of what’s known as stuffed.although still functioning. Raid 6 is the same as 5 but with one more safety drive. Raid 10 although the costly option still what I call the best option your covered very well And I highly suggest hardware raid over software raid, The hardware opton to me gives better options for recovery or getting things back on line. From: macvisionaries@googlegroups.com <macvisionaries@googlegroups.com> On Behalf Of Steve Matzura Sent: Wednesday, 19 December 2018 2:31 PM To: macvisionaries@googlegroups.com Subject: Re: 4 tb hd, what is the best backup plan? 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 -- The following information is important for all members of the Mac Visionaries list. If you have any questions or concerns about the running of this list, or if you feel that a member's post is inappropriate, please contact the owners or moderators directly rather than posting on the list itself. Your Mac Visionaries list moderator is Mark Taylor. 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