I was using the literal definition (to append linearly) Striping places a cylinder of each drive in order after the previous from another drive. It’s a bit different from simply appending a drive into the filesystem.
Thanks for the correction though. Btw, trying to recover files from a striped raid is a real pain in the A$$ because of how files are written in the filesystem. Basically, if you lose any 1 drive in that type of raid, you are effectively screwed. That’s the nice thing about mirroring. It creates a mirrored image on another drive of identical specification and then writes a CRC checksum to a primary drive (if all you have is 3, then the primary is drive 1 and the two mirrored are 2 and 3 respectively. When adding to such a raid, you must always add 2 drives. Btw, if 1 drive (other than the CRC drive) Fails, then recovery is as simple as removing the bad drive, inserting new and issuing the mirror command. Anyway, that’s about the extent of my knowledge (I have used raid partitions before, but right now, I don’t have 1 setup.) -Eric > On Dec 18, 2018, at 6:30 PM, Steve Matzura <numb...@noisynotes.com> wrote: > > 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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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. You can reach mark at: mk...@ucla.edu and your owner is Cara Quinn - you can reach Cara at caraqu...@caraquinn.com The archives for this list can be searched at: http://www.mail-archive.com/macvisionaries@googlegroups.com/ --- You received this message because you are subscribed to the Google Groups "MacVisionaries" group. To unsubscribe from this group and stop receiving emails from it, send an email to macvisionaries+unsubscr...@googlegroups.com. To post to this group, send email to macvisionaries@googlegroups.com. Visit this group at https://groups.google.com/group/macvisionaries. For more options, visit https://groups.google.com/d/optout.
