Question: SSD L2 smart? Topic is solved

[escaward]

Hello Romex,

Question 1: One SSD Only (OS + L2 on same SSD)
If I have C: on SSD1, E: as PrimoCache L2 on SSD1, D: HDD, and Z: HDD would the E: L2 cache on SSD1 be smart enough to not cache any READ data from C: as it is the same SSD1?

Question 2: One OS SSD and One L2 SSD
If I have C: on SSD1, E: as PrimoCache L2 on SSD2, D: HDD, and Z: HDD would the E: L2 cache on SSD2 be smart enough to not cache any READ data from C: as it is an SSD?

Regards,
escaward

PS. I am currently in Question 1 mode with my OS and L2 on the same SSD and it looks like I am not seeing any L2Storage Writes.

[BonzaiDuck]

The situation #1 would only occur if you chose to cache the C : drive to itself. If C : is not included in any caching task using the L2 cache, then no read data will be cached on the SSD. You can cache the C : drive to RAM, and give it 0 bytes for using a caching L2 SSD volume.

Those choices are in the configuration dialog for each caching task. My advice, given the nature of your questions, gets a preamble: PrimoCache is a versatile Swiss Knife of storage caching. But simple is best. You don't NEED to cache to RAM a drive cached to a dedicated SSD volume. You don't NEED to cache your OS-boot-system volume on the same physical disk to the L2 volume that is on that physical disk.

If you compare -- for certain usage profiles -- the benchies for caching an HDD to RAM and caching an HDD to both RAM and SSD, I don't think you'll see a difference. Support tells us that the SSD-caching occurs when the system is idle, and doesn't show up in benchies for version 2.7.x Figure the SSD-caching of an HDD will be in range of 80% of the SSD's own performance. Depending on how much data needs to remain in the cache, a RAM cache may show considerably more performance even if only a few GB of RAM are allocated.

It used to be the case that a regular SATA SSD worked wonders with a large capacity HDD -- and it still does. But NVMe M.2 SSDs increase the speed improvement by maybe a factor of 10x for an HDD and 4x for an SATA SSD. It changes the whole ball-game. Yet the same imperatives apply: Don't cache one volume on the same SSD to an L2 on that SSD. At best, it just consumes additional clock-cycles. At worst, I wouldn't be able to say. But for the data on the non-L2 Volume, there would be no improvement, would there?

[Support]

Question 1: One SSD Only (OS + L2 on same SSD)If I have C: on SSD1, E: as PrimoCache L2 on SSD1, D: HDD, and Z: HDD would the E: L2 cache on SSD1 be smart enough to not cache any READ data from C: as it is the same SSD1?

Yes, PrimoCache recognizes such scenario and will not cache any read data from C: even you enable L2 caching for C:.

Question 2: One OS SSD and One L2 SSDIf I have C: on SSD1, E: as PrimoCache L2 on SSD2, D: HDD, and Z: HDD would the E: L2 cache on SSD2 be smart enough to not cache any READ data from C: as it is an SSD?

No. PrimoCache cannot recognize this case and will cache read data from C:.
Users may use a faster SSD to speed up a slow SSD, so we don't automatically bypass read data from a drive just because it is a SSD.

[BonzaiDuck]

I would like to ask a question, Support.

Escaward's questions refer to the caching volume as "E :" -- implying that he gave a disk letter to the volume.

From the standpoint of PrimoCache operation, would it at all make a difference as to how it worked with or without the drive letter?

What are the drawbacks -- if any -- of assigning a drive letter? And what are the drawbacks of removing any drive-letter assignment?

I personally wouldn't think it would matter, but the drive letter exposes the caching volume to the OS's file management and programs, like "File Explorer" or "Windows Explorer." That's the personal basis I have for avoiding drive-letter assignment.

[Support]

@BonzaiDuck, no difference for PrimoCache with or without the drive letter. It is recommended to remove the drive letter, thus Windows explorer won't see this volume that is not recognized by Windows and won't pop up a message box to ask you if format it.
Actually PrimoCache automatically remove the drive letter when you convert a normal volume to a L2Storage volume.