Write speed and flashdrive endurance


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Greetings,

 

I have three concerns before using unraid:

1. In case I have two HDD drives (not counting a parity one) does UnRAID put some files on 1hdd and other files on 2hdd? I've seen complaints about unraid write speed limited to speed of one hdd. Is it mitigated somehow, not counting SSD cache?
 

2. Does unraid do any pendrive endurance actions? Like its own quasi-trim? Or dividing a pendrive to X segments and migrating itself to next one every X time to avoid nand burning?

 

3. Some people here mention dreaded HBA controllers from LSI (FreeNAS-related problems with MB/RAID SATA ports). So I am concerned - does unRAID need special controlers? Or can I use happily 8xSATA from X570 w/o any problems?

 

CobraPL

Edited by CobraPL
Added Q3
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Unraid IS NOT RAID. There is no striping. Each disk is an independent filesystem. Each file exists completely on a single disk. Folders can span disks, this is known as User Shares. There is also a parity disk which provides redundancy so a missing disk can be recreated from reading all other disks.

 

This makes Unraid slower than striped RAID, but it also makes it possible to use different sized disks in the array, disks not being used can be spun down, and since each data disk is an independent filesystem, they can be read by themselves on any linux.

 

Reading is at the speed of the disk being read. Write speed is somewhat slower since parity is updated realtime.

 

There is also faster storage (pools) usually SSDs and these can have redundancy (btrfs raid modes) and can work with the parity array to cache User Share writes to be moved to the slower parity array later.

 

If by pendrive you mean the boot flash drive, it is mostly only accessed at boot time, and written when you make configuration changes. The boot flash is not the Operating System, it just contains the archives of the OS. These archives are unpacked fresh from the boot flash at each boot into RAM, and the OS runs completely in RAM. Configuration settings you make in the webUI are written to the boot flash so they can be reapplied at boot. Other than that the boot flash isn't written much.

 

 

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Regarding #3, the main disk controller issue is with any that uses a Marvell chipset (whether on the motherboard or on an add-in board).    Port multipliers can also be problematical.  This is a generic Linux issue with recent kernels and is not unRaid specific.
 

Not sure why you talk about the ‘dreaded’ LSI HBA controllers - ones based on thenLSI chipset have proved to be the most reliable, although they do need to be flashed to IT mode rather than RAID mode for unRaid to be able to use them optimally.

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5 hours ago, itimpi said:

Regarding #3, the main disk controller issue is with any that uses a Marvell chipset (whether on the motherboard or on an add-in board).    Port multipliers can also be problematical.  This is a generic Linux issue with recent kernels and is not unRaid specific.
 

Not sure why you talk about the ‘dreaded’ LSI HBA controllers - ones based on thenLSI chipset have proved to be the most reliable, although they do need to be flashed to IT mode rather than RAID mode for unRaid to be able to use them optimally.

Yeah, LSI HBAs are brilliant, but FreeNAS problem with SATA is dreaded. FreeNAS/TrueNAS has a lot of critical pitfalls. Have mobo's AHCI SATA? All data lost.

I look at hardware requirements. There are no AMD SATA controllers there.

Is X570 so much problematic? Is the issue common?


 

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