Raid in SSD issue with Trim

Question

Yesterday I posted a question about Storage Spaces and ReFS about cache turn off (write through mode) and it's settled. I thought it will be simple, but it turns out far from simple and ran into another issue. Storage Spaces doesn't recommend having TRIM turn on for stripe SSD and ReFS is not recommended for database usage yet (from a couple of discussion in the forum). Which is a major downfall, ouch. I have to change plan now.

I'm having 2 SSD Intel S3710 which I will RAID as RAID 1. The problem is Intel only supports trim at RAID 0 level. I'm hoping at RAID 1, but it doesn't! Ouch!

So I'm thinking of a couple of solutions now :

1. Continue with RAID 0 with Intel SSD Trim supports and use it in conjunction with Stabelbit Drivepool and Scanner. I have no experience with Stablebit at all. Will SB Drivepool able to detect changes made in the file which has already copied? Example: You have a word or excel file that keeps growing because the changes are made every day, the database grows larger and larger too. Will SB Drivepool able to detect these changes and accommodate it at the duplicated files as well? If yes, then it will behave more like RAID 1.

2. Can I use RAID 0 and put it in SB Pool? If yes, then which drive letters will appear on screen? The native Intel Raid or The Drivepool version? Excuse my newbies question for this one.

3. If the answer is no, I cannot combine it. Does Stablebit Drivepool support SSD Trim in a pool? Say I combine all S3710 SSD inside, can I have the TRIM supports too?

4. Other solution that supports Software RAID with Trim (other than RAID 0). I have done a lot of research but NO definitive answer. SnapRAID, FlexRaid, etc, etc. I just assume that it isn't possible in any way. Any suggestion?

Any advice/suggestion is greatly appreciated!

Thanks! Rivai

Answer 1

Intel S3710 SSD are very consistent enterprise drives. You simply don't need to worry about TRIM on these drives.

Answer 2

I have the same question too. I got some information.

SoftRaid

OpenZFS

openzfs trim support in freebsd

ZOL not release, DO NOT APPLY THIS PATCH IF YOU CARE ABOUT YOUR DATA

MDADM

Since version 3.7 of the Linux kernel mainline, md supports TRIM operations for the underlying solid-state drives, for linear, RAID 0, RAID 1, RAID 5 and RAID 10 layouts

CentOS 6.5 The mdadm tool now supports the TRIM commands for RAID0, RAID1, and RAID10.

Hardware Raid

Avago LSI

LSI Check Interoperability and Compatibility

You can make sure the device in the interoperability and compatibility list. Intel DC S3710 has no problem. I 'm not found any messages about ssd trim, only LSI Fastpath to optimize ssd raid (raid 0,raid 5) LSI-PB-MR-FastPath

HP Raid

(source)
TRIM is supported on various SSDs when using RAID (1,0,10), but I 'm found anything in HP raid controller spec file.
I guess the same support with Dell and LSI.

Microsoft softraid

And the document show could support trim when using RAID(0,1,5)

SSD Over-provisioning

Good news is there are more Over-provisioning in Intel DC S3710. The DC S3710 leverages BGA-mounted 20nm 128Gb NAND. Over-provisioning varies based upon capacity, but ranges between 30 to 40 percent
Compare with DC S3610 and DC S3510, if you write full your SSD, Over-provisioning will hold the performance, reduce the effect by garbage collection.

If you want make sure the size of Over-provisioning. There are a lot of documents about "Enable HPA". SSD_Over-provisioning_using_hdparm#Enabling_the_Host_Protected_Area

For example

User Capacity:    900,184,411,136 bytes [900 GB]
awk 'BEGIN{print 900184411136/1024/1024/1024}'
838.362
hdparm -N /dev/sdb
max sectors = 1953525168/1953525168, HPA is disabled
awk 'BEGIN{print 1953525168*512/1024/1024/1024}'
931.513

In my example about 11% Over-provisioning.

Ext4 trim
⁠XFS Online Discard Support
How these hardware connect is another problem, you need avoid the bottle neck.

DMI bandwidth DMI 2.0, introduced in 2011, doubles the data transfer rate to 2 GB/s with a ×4 link. It is used to link an Intel CPU with the Intel Platform Controller Hub (PCH), which supersedes the historic implementation of a separate northbridge and southbridge.

DMI 3.0, released in August 2015, allows the 8 GT/s transfer rate per lane, for a total of four lanes and 3.93 GB/s for the CPU–PCH link. It is used by two-chip variants of the Intel Skylake microprocessors, which are used in conjunction with Intel 100 Series chipsets

I suggest extend more SATA SSD raid volume (large than 4(DMI2) or 6(DMI3)) by PCIE Gen3/4 x8/x16 adapter.

If your OS are not freebsd, I think mdadm + ext4 is a good choice.