And I still don't understand the appeal of a mirroring RAID system (e.g., RAID10) over, say, RAID5 plus redundant on- and off-site HDD backups. Yes it provides more protection against some failure in the RAID itself, but not against all the other stuff that can bite you... OS burps, viruses, surges, operator headspace errors, etc.[a href=\"index.php?act=findpost&pid=95485\"][{POST_SNAPBACK}][/a]
The main advantages of RAID 10 are the better redundancy (under certain circumstances), faster write times, and the fact that you could recover the whole array from a single disk from each mirror pair. I use it in my data array but my backup array which has the last 3-5 images of each of my logical system & data disks is RAID 5. My system disk is striped (RAID 0, which as Jani mentions has no redundancy).
When working your storage strategy, you need to keep in mind everyone's storage requirements have differences. My basic average requirement per single photo image adds up to around 220MB, 20MB for the raw 17MPxl file and 200MB for the working PSD. I could store maybe 18-20 in a DVD ... This is very different from Nil's, who has much smaller files but many, many more. How the storage configuration responds to his files will be very different from my files.
To sumarize:
- It cannot be over-emphasized, RAID (especially 0!) does not replace backups. It's complementary technology that can make your life more trouble-free and save you time when used properly.
- RAID 0 is strictly for performance, the more spindles (drives) the faster, but also more fragile. You lose one drive and you've lost the whole array content, not just the one drive's. 2 drives are almost not worth it but you get to 4 and you're flying. Get smaller drives because they add up. And DO NOT use more than one partition actively or you'll lose the performance advantage. IMO best for system and scratch disks.
- RAID 1 uses mirrored pairs, so you can lose one drive of each mirror and survive. You lose half the storage capacity of the combined disks. It has noticeably better write performance than RAID 5 because it doesn't have to calculate parity, but slower reads because it is not striped. Safe but slow.
- RAID 5 uses parity for redundancy and stripes the drives. You lose only 1 drive's worth of storage capacity so you can get relatively inexpensive huge capacities. Fast reads, writes similar to a single drive. You can lose 1 drive and function. IMO good for backup of several drive images.
- RAID 6 is like RAID 5 but uses a second drive for redundant parity. You can lose 2 drives and function, but you lose 2 drives from storage capacity. IMO best for backup if you can afford it.
- RAID 10 uses two or more RAID 1 mirrored pairs and stripes them (RAID 1, + RAID 0 on top) so it's much faster than RAID 1. Needs at least 4 drives. A 4-drive RAID 10 reads as fast as a 3-drive RAID 5 because it's in pairs, but writes faster than a 4-drive RAID 5. IMO best for data if you can afford it.
- Keep in mind that in striped arrays (0, 10, 5, 6) speed is gained from separate drives being accessed. A 4-drive RAID 5 will read faster than a 4-drive RAID 10 because the RAID 5 is accessing 3 spindles and the R10 only 2 (one in each mirror).
Hope I got it down clearly and correctly ...