raid10.. how many drives can fail and still have the array in tact? (4 drives/8 drives)
in [Storage]
|
Prev: raid10.. how many drives can fail and still have the array in tact? (4 drives/8 drives)
Next: What Determines Which Drive Is HD0?
From: Arno Wagner on 20 Dec 2007 08:45 Previously markm75 <markm75c(a)msn.com> wrote: > On Dec 20, 1:35 am, Arno Wagner <m...(a)privacy.net> wrote: >> Previously markm75 <markm...(a)msn.com> wrote: >> > With a 4 drive raid10.. i'm a little unclear on how many can fail here >> > and still work.. >> >> A raid 10 uses RAID1 components as basis to build a RAID 0 on >> top. If in any of the RAID1 subcomponents two drives fail, the >> whole array fails. >> >> For 4 drives that would be two RAID1 pairs. If 1 drive fails, >> the array works. If 2 drives fail, it may or may not work. >> 3 drives kill oit reliably. >> >> > Same with 8 drive? >> >> That would be 4 RAID1 pairs. >> >> 1 drive failure will not kill it. 2-4 drive failures may or may >> not kill it, depending on whcih drives fail. 5 drives reliably >> kill the array. >> >> Arno > So basically with 4 drive.. there are two on each side.. if 1 drive on > one side dies.. its ok.. but if 1 drive on each side dies then its a > goner.. if 2 drives fail on one side.. i'd think it would be ok, just > not mirrored.. Exactly. > I'm trying to decide for my beefy virtual hosting server and file > server what to do.. i have 8, 500gb drives.. > i originally was going to do 4 drive raid 5 for the main filesharing/ > shares area.. then raid10 4 drive, for the virtual servers being > hosted on this box (8 of them, only 3 remotely beefy i guess).. i'd > prefer an all in one solution, but that would mean either going 8 > drive raid5 (which would be horribly slow on rebuilds) or 8 drive > raid10, which sounds a little risky but fast on writes. You should determine what your bottlenecks are first. You may even have time for RAID6 without knowing it. Arno
From: Arno Wagner on 20 Dec 2007 18:48 Previously markm75 <markm75c(a)msn.com> wrote: > On Dec 20, 8:45 am, Arno Wagner <m...(a)privacy.net> wrote: >> Previously markm75 <markm...(a)msn.com> wrote: >> > On Dec 20, 1:35 am, Arno Wagner <m...(a)privacy.net> wrote: >> >> Previously markm75 <markm...(a)msn.com> wrote: >> >> > With a 4 drive raid10.. i'm a little unclear on how many can fail here >> >> > and still work.. >> >> >> A raid 10 uses RAID1 components as basis to build a RAID 0 on >> >> top. If in any of the RAID1 subcomponents two drives fail, the >> >> whole array fails. >> >> >> For 4 drives that would be two RAID1 pairs. If 1 drive fails, >> >> the array works. If 2 drives fail, it may or may not work. >> >> 3 drives kill oit reliably. >> >> >> > Same with 8 drive? >> >> >> That would be 4 RAID1 pairs. >> >> >> 1 drive failure will not kill it. 2-4 drive failures may or may >> >> not kill it, depending on whcih drives fail. 5 drives reliably >> >> kill the array. >> >> >> Arno >> > So basically with 4 drive.. there are two on each side.. if 1 drive on >> > one side dies.. its ok.. but if 1 drive on each side dies then its a >> > goner.. if 2 drives fail on one side.. i'd think it would be ok, just >> > not mirrored.. >> >> Exactly. >> >> > I'm trying to decide for my beefy virtual hosting server and file >> > server what to do.. i have 8, 500gb drives.. >> > i originally was going to do 4 drive raid 5 for the main filesharing/ >> > shares area.. then raid10 4 drive, for the virtual servers being >> > hosted on this box (8 of them, only 3 remotely beefy i guess).. i'd >> > prefer an all in one solution, but that would mean either going 8 >> > drive raid5 (which would be horribly slow on rebuilds) or 8 drive >> > raid10, which sounds a little risky but fast on writes. >> >> You should determine what your bottlenecks are first. You >> may even have time for RAID6 without knowing it. >> >> Arno- Hide quoted text - >> >> - Show quoted text - > Hi there.. > What did you mean by that ...(bottlenecks).. Slowest components that matter. > RAID6.. how many drives can fail here.. is it the same as raid5.. i > have forgotten.. i think there was extra parity? RAID6 can survive loss of any two disks. Since parity is not enough, it will be slow with two failed drives. > So raid6, 8 drives of 500gb.. does this still equate to 3.5TB? 3TB. > I didnt think the writes were any better with raid6 than raid5.. i've > always been a fan of the writes of raid10. RAID6 is about good redundancy. Arno
From: Arno Wagner on 20 Dec 2007 18:51 Previously markm75 <markm75c(a)msn.com> wrote: > On Dec 20, 8:45 am, Arno Wagner <m...(a)privacy.net> wrote: >> Previously markm75 <markm...(a)msn.com> wrote: >> > On Dec 20, 1:35 am, Arno Wagner <m...(a)privacy.net> wrote: >> >> Previously markm75 <markm...(a)msn.com> wrote: >> >> > With a 4 drive raid10.. i'm a little unclear on how many can fail here >> >> > and still work.. >> >> >> A raid 10 uses RAID1 components as basis to build a RAID 0 on >> >> top. If in any of the RAID1 subcomponents two drives fail, the >> >> whole array fails. >> >> >> For 4 drives that would be two RAID1 pairs. If 1 drive fails, >> >> the array works. If 2 drives fail, it may or may not work. >> >> 3 drives kill oit reliably. >> >> >> > Same with 8 drive? >> >> >> That would be 4 RAID1 pairs. >> >> >> 1 drive failure will not kill it. 2-4 drive failures may or may >> >> not kill it, depending on whcih drives fail. 5 drives reliably >> >> kill the array. >> >> >> Arno >> > So basically with 4 drive.. there are two on each side.. if 1 drive on >> > one side dies.. its ok.. but if 1 drive on each side dies then its a >> > goner.. if 2 drives fail on one side.. i'd think it would be ok, just >> > not mirrored.. >> >> Exactly. >> >> > I'm trying to decide for my beefy virtual hosting server and file >> > server what to do.. i have 8, 500gb drives.. >> > i originally was going to do 4 drive raid 5 for the main filesharing/ >> > shares area.. then raid10 4 drive, for the virtual servers being >> > hosted on this box (8 of them, only 3 remotely beefy i guess).. i'd >> > prefer an all in one solution, but that would mean either going 8 >> > drive raid5 (which would be horribly slow on rebuilds) or 8 drive >> > raid10, which sounds a little risky but fast on writes. >> >> You should determine what your bottlenecks are first. You >> may even have time for RAID6 without knowing it. >> >> Arno- Hide quoted text - >> >> - Show quoted text - > btw.. it took 10hr 37 min for my 4 drive (500gb each) raid5 set to > build on this card.. and it took 1hr 41 min for the raid10 4 drive set > to build. The RAID10 time is standard. The RAID5 time is extremely poor. I have a 8 500GB disk software RAID6 on older hardware, that builds in about 4 hours on Linux. Arno
From: Arno Wagner on 20 Dec 2007 18:52 Previously markm75 <markm75c(a)msn.com> wrote: > On Dec 20, 8:45 am, Arno Wagner <m...(a)privacy.net> wrote: >> Previously markm75 <markm...(a)msn.com> wrote: >> > On Dec 20, 1:35 am, Arno Wagner <m...(a)privacy.net> wrote: >> >> Previously markm75 <markm...(a)msn.com> wrote: >> >> > With a 4 drive raid10.. i'm a little unclear on how many can fail here >> >> > and still work.. >> >> >> A raid 10 uses RAID1 components as basis to build a RAID 0 on >> >> top. If in any of the RAID1 subcomponents two drives fail, the >> >> whole array fails. >> >> >> For 4 drives that would be two RAID1 pairs. If 1 drive fails, >> >> the array works. If 2 drives fail, it may or may not work. >> >> 3 drives kill oit reliably. >> >> >> > Same with 8 drive? >> >> >> That would be 4 RAID1 pairs. >> >> >> 1 drive failure will not kill it. 2-4 drive failures may or may >> >> not kill it, depending on whcih drives fail. 5 drives reliably >> >> kill the array. >> >> >> Arno >> > So basically with 4 drive.. there are two on each side.. if 1 drive on >> > one side dies.. its ok.. but if 1 drive on each side dies then its a >> > goner.. if 2 drives fail on one side.. i'd think it would be ok, just >> > not mirrored.. >> >> Exactly. >> >> > I'm trying to decide for my beefy virtual hosting server and file >> > server what to do.. i have 8, 500gb drives.. >> > i originally was going to do 4 drive raid 5 for the main filesharing/ >> > shares area.. then raid10 4 drive, for the virtual servers being >> > hosted on this box (8 of them, only 3 remotely beefy i guess).. i'd >> > prefer an all in one solution, but that would mean either going 8 >> > drive raid5 (which would be horribly slow on rebuilds) or 8 drive >> > raid10, which sounds a little risky but fast on writes. >> >> You should determine what your bottlenecks are first. You >> may even have time for RAID6 without knowing it. >> >> Arno- Hide quoted text - >> >> - Show quoted text - > From looking at this description.. it would appear that all but one > drive can fail on each side and the array still works? > http://en.wikipedia.org/wiki/Nested_RAID_levels#RAID_1.2B0 (so 4 on > each side, 3 can fail on each side in raid10)? No. Example: If A1 and A1 fail, the whole array is broken.
From: Arno Wagner on 20 Dec 2007 18:53
Previously markm75 <markm75c(a)msn.com> wrote: > On Dec 20, 8:45 am, Arno Wagner <m...(a)privacy.net> wrote: >> Previously markm75 <markm...(a)msn.com> wrote: >> > On Dec 20, 1:35 am, Arno Wagner <m...(a)privacy.net> wrote: >> >> Previously markm75 <markm...(a)msn.com> wrote: >> >> > With a 4 drive raid10.. i'm a little unclear on how many can fail here >> >> > and still work.. >> >> >> A raid 10 uses RAID1 components as basis to build a RAID 0 on >> >> top. If in any of the RAID1 subcomponents two drives fail, the >> >> whole array fails. >> >> >> For 4 drives that would be two RAID1 pairs. If 1 drive fails, >> >> the array works. If 2 drives fail, it may or may not work. >> >> 3 drives kill oit reliably. >> >> >> > Same with 8 drive? >> >> >> That would be 4 RAID1 pairs. >> >> >> 1 drive failure will not kill it. 2-4 drive failures may or may >> >> not kill it, depending on whcih drives fail. 5 drives reliably >> >> kill the array. >> >> >> Arno >> > So basically with 4 drive.. there are two on each side.. if 1 drive on >> > one side dies.. its ok.. but if 1 drive on each side dies then its a >> > goner.. if 2 drives fail on one side.. i'd think it would be ok, just >> > not mirrored.. >> >> Exactly. >> >> > I'm trying to decide for my beefy virtual hosting server and file >> > server what to do.. i have 8, 500gb drives.. >> > i originally was going to do 4 drive raid 5 for the main filesharing/ >> > shares area.. then raid10 4 drive, for the virtual servers being >> > hosted on this box (8 of them, only 3 remotely beefy i guess).. i'd >> > prefer an all in one solution, but that would mean either going 8 >> > drive raid5 (which would be horribly slow on rebuilds) or 8 drive >> > raid10, which sounds a little risky but fast on writes. >> >> You should determine what your bottlenecks are first. You >> may even have time for RAID6 without knowing it. >> >> Arno- Hide quoted text - >> >> - Show quoted text - > Btw.. forgot.. that 10hr build time was a background build, not > foreground and the raid10 time was foreground only. What is a background build? Arno |