May 2, 201610 yr Hi All, I recently decided to awake my old Dell PowerEdge T410 to turn it into my new virtualization rig (it was asleep because it make to much noise...). Inside I actually have a PERC 200 with 4 x 300 GB SAS 15K disks. I plan to use them as cache in a RAID 10 configuration (600 GB then), but would it be better to get 2 SSD (500 GB in RAID 1) instead ? Is this supported in Unraid to set a hardware RAID 10 as a Cache ? (weird to set a Raid un UnRaid, I know). When I bought this server SAS 15k where the recommandation for I/O performance, but how does it compare to SSD ? I forgot to mention that I will use UnRaid for NAS, Virtualization (several big VMs), and maybe gaming if I find which GPU I can add to this rig. best regards, STEMax
May 2, 201610 yr I'm also interested to know if I can create a RAID0 with SSDs and use them as cache + another SSD for parity
May 2, 201610 yr If you have the hardware to create the RAID volume(s), unRaid will happily make use of them. My 8TB parity "drive" is actually a 2x 4TB RAID0 volume.
May 2, 201610 yr I'm also interested to know if I can create a RAID0 with SSDs and use them as cache + another SSD for parity You can use BTRFS RAID0 on SSDs and use them for cache if you want to, but the use of an SSD as a parity drive is not supported.
May 2, 201610 yr I'm also interested to know if I can create a RAID0 with SSDs and use them as cache + another SSD for parity You can use BTRFS RAID0 on SSDs and use them for cache if you want to, but the use of an SSD as a parity drive is not supported. Oh, I was almost sure that you could select an SSD drive to be a parity of another SSD acting as cache . How do you do to make sure your cache data is safe then? just back it up to your HDDs?
May 2, 201610 yr I'm also interested to know if I can create a RAID0 with SSDs and use them as cache + another SSD for parity You can use BTRFS RAID0 on SSDs and use them for cache if you want to, but the use of an SSD as a parity drive is not supported. Oh, I was almost sure that you could select an SSD drive to be a parity of another SSD acting as cache . How do you do to make sure your cache data is safe then? just back it up to your HDDs? When you said "parity" I assumed you meant unRAID's parity disk(s). Do you actually mean some form of protection for the cache disk? If you do then just use BTRFS for the cache pool. If you then have a cache pool of two SSDs they will be set up as a RAID1 mirror. So a pair of 250 GB SSDs would give you 250 GB of protected cache. If that isn't enough you could use four 250 GB SSDs to give you 500 GB of protected cache. Various other combinations are also possible, such as three 250 GB SSDs to give you 375 GB protected, or two 250 GB and one 500 GB to give you 500 GB protected.
May 2, 201610 yr I'm also interested to know if I can create a RAID0 with SSDs and use them as cache + another SSD for parity You can use BTRFS RAID0 on SSDs and use them for cache if you want to, but the use of an SSD as a parity drive is not supported. Oh, I was almost sure that you could select an SSD drive to be a parity of another SSD acting as cache . How do you do to make sure your cache data is safe then? just back it up to your HDDs? When you said "parity" I assumed you meant unRAID's parity disk(s). Do you actually mean some form of protection for the cache disk? If you do then just use BTRFS for the cache pool. If you then have a cache pool of two SSDs they will be set up as a RAID1 mirror. So a pair of 250 GB SSDs would give you 250 GB of protected cache. If that isn't enough you could use four 250 GB SSDs to give you 500 GB of protected cache. Various other combinations are also possible, such as three 250 GB SSDs to give you 375 GB protected, or two 250 GB and one 500 GB to give you 500 GB protected. Thanks! My idea was to improve the speed by doing a RAID0 (2x250gb = 500gb RAID0) and use another SSD for example a 500GB for parity. If there's no support for parity per se, then I guess I would need to do 2xRAID0 in RAID1?. BTW, the RAID is created on unRAID or is it created on MB's RAID controller?
May 2, 201610 yr Author Hi Guys, Thanks for the answer, I will go for a RAID 10 then and see if it's ok, may be I'll switch to a Cache Pool of SSD if things seems to slow (but I doubt it for now). Best regards STEMax
May 2, 201610 yr Hi All, I recently decided to awake my old Dell PowerEdge T410 to turn it into my new virtualization rig (it was asleep because it make to much noise...). Inside I actually have a PERC 200 with 4 x 300 GB SAS 15K disks. I plan to use them as cache in a RAID 10 configuration (600 GB then), but would it be better to get 2 SSD (500 GB in RAID 1) instead ? Is this supported in Unraid to set a hardware RAID 10 as a Cache ? (weird to set a Raid un UnRaid, I know). When I bought this server SAS 15k where the recommandation for I/O performance, but how does it compare to SSD ? I forgot to mention that I will use UnRaid for NAS, Virtualization (several big VMs), and maybe gaming if I find which GPU I can add to this rig. best regards, STEMax The right SSDs will outperform 15k SAS drives, easily. IOPS for SAS is measured in 100s, and for SSD 10,000s. Now I am not sure you will notice that difference without a performance benchmarking tool But you will notice they are quieter, and consume less power, and generate less heat.
May 2, 201610 yr I'm also interested to know if I can create a RAID0 with SSDs and use them as cache + another SSD for parity You can use BTRFS RAID0 on SSDs and use them for cache if you want to, but the use of an SSD as a parity drive is not supported. Oh, I was almost sure that you could select an SSD drive to be a parity of another SSD acting as cache . How do you do to make sure your cache data is safe then? just back it up to your HDDs? When you said "parity" I assumed you meant unRAID's parity disk(s). Do you actually mean some form of protection for the cache disk? If you do then just use BTRFS for the cache pool. If you then have a cache pool of two SSDs they will be set up as a RAID1 mirror. So a pair of 250 GB SSDs would give you 250 GB of protected cache. If that isn't enough you could use four 250 GB SSDs to give you 500 GB of protected cache. Various other combinations are also possible, such as three 250 GB SSDs to give you 375 GB protected, or two 250 GB and one 500 GB to give you 500 GB protected. Thanks! My idea was to improve the speed by doing a RAID0 (2x250gb = 500gb RAID0) and use another SSD for example a 500GB for parity. If there's no support for parity per se, then I guess I would need to do 2xRAID0 in RAID1?. BTW, the RAID is created on unRAID or is it created on MB's RAID controller? unRAID isn't RAID and doesn't need a RAID controller to perform any of its functions. That said, some people use hardware RAID cards to trick unRAID into thinking a pair of small disks are in fact a single large one. The 2 x 250 + 500 question was answered above (quoted in bold). The cache SSDs are managed by BTRFS and this provides the protection you require. All you need to do is assign the three SSDs to the cache pool and it intelligently lays out the data across them, ensuring that there are two copies of each block on different devices. Like I said, if you talk about parity in the unRAID forum people assume you mean the parity that protects the main unRAID array.
May 3, 201610 yr Author The right SSDs will outperform 15k SAS drives, easily. IOPS for SAS is measured in 100s, and for SSD 10,000s. Now I am not sure you will notice that difference without a performance benchmarking tool But you will notice they are quieter, and consume less power, and generate less heat. Thanks for the update. I will try with the SAS 15K and then update to SSD if needed. I'm not to much concerned by the noise as this server will not be stored in my house Best regards STEMax
May 7, 201610 yr thanks John_M! I had no idea BTRFS was that smart setting up the disks. I'm clear that if I have 250gb+250gb+500gb, that will be effectively a 2x250 RAID0 + 500GB for redundancy. However, the RAID0 will outperform the 500gb disk alone... would this affect the performance of the RAID0*? Also, how is supposed to work when I have 3x250 drives? Would I get the performance of a RAID0? *sorry for saying "RAID0", I'm not entirely sure if the BTRFS system creates a RAID0 or something else that is called differently.
Archived
This topic is now archived and is closed to further replies.